2016 data analysis update - project clean water

EXHIBIT E 2016 Data Analysis Update

Final

EFFECTIVENESS ASSESSMENT MONITORING FOR THE SAN DIEGO HYDROMODIFICATION MANAGEMENT PLAN

2016 Data Analysis Update

Prepared for November 2016 County of San Diego and Municipal Copermittees

Final

EFFECTIVENESS ASSESSMENT MONITORING FOR THE SAN DIEGO HYDROMODIFICATION MANAGEMENT PLAN


Prepared for November 2016 County of San Diego and Municipal Copermittees

Click here and down arrow to select office address

Irvine

Los Angeles

Oakland

Orlando

Pasadena

Petaluma

Portland

Sacramento

San Diego

San Francisco

Santa Monica

Seattle

Tampa

Woodland Hills

140075.07

OUR COMMITMENT TO SUSTAINABILITY | ESA helps a variety of public and private sector clients plan and prepare for climate change and emerging regulations that limit GHG emissions. ESA is a registered assessor with the California Climate Action Registry, a Climate Leader, and founding reporter for the Climate Registry. ESA is also a corporate member of the U.S. Green Building Council and the Business Council on Climate Change (BC3). Internally, ESA has adopted a Sustainability Vision and Policy Statement and a plan to reduce waste and energy within our operations. This document was produced using recycled paper.

TABLE OF CONTENTS San Diego HMP – 2016 Data Analysis Update

Page

I. Introduction..................................................................................................................... 1

II. HMP Monitoring Background........................................................................................ 1 A. Low-Flow Thresholds ................................................................................................... 2 B. Receiving Channel Monitoring Sites ............................................................................ 3 C. BMP Monitoring Sites .................................................................................................. 5

III. Question 1 – Validity of Low-Flow Thresholds ........................................................... 5 A. Approach ...................................................................................................................... 5 B. Data Collection ............................................................................................................. 6 C. Data Analysis ............................................................................................................... 9

i. Peak Discharge Estimates ................................................................................... 9 ii. Rating Curve Analysis ......................................................................................... 9 iii. Event-based Work Curves.................................................................................. 9

D. Results and Discussion ............................................................................................. 10 i. Peak Discharge Estimates ................................................................................. 10 ii. Rating Curve Analysis ....................................................................................... 11 iii. Event-based Work Curves................................................................................ 12 iv. Comparison of Results ..................................................................................... 12

IV. Question 2 – Performance of Flow-Control BMPs ................................................... 14 A. Approach .................................................................................................................... 14 B. Data Collection ........................................................................................................... 14 C. Data Analysis ............................................................................................................. 14 D. Results and Discussion ............................................................................................. 15

V. Question 3 – Stability of Receiving Channels ........................................................... 17 A. Approach .................................................................................................................... 17 B. Data Collection ........................................................................................................... 18 C. Data Analysis ............................................................................................................. 20 D. Results and Discussion ............................................................................................. 20

i. Changes in Channel Cross Section and Profile ................................................ 20 ii. Channel Slope Comparisons ............................................................................ 24 iii. Summary of Channel Changes ........................................................................ 24

VI. Conclusions .................................................................................................................. 25 A. Effectiveness Assessment ......................................................................................... 25

VII. References .................................................................................................................... 27

VIII. List of Preparers ........................................................................................................... 29

San Diego HMP – 2016 Data Analysis Update i ESA / 140075.07 Technical Report September 2016

Table of Contents

Page

Appendices A. Analytical Examples ........................................................................................................ A-1 B. Rating Curves .................................................................................................................. B-1 C. Work Curves .................................................................................................................... C-1 D. Channel Surveys ............................................................................................................. D-1

List of Figures Figure 1 Phased monitoring approach (Source: Weston, 2014) .......................................... 2 Figure 2 Overview of monitoring sites (Source: Weston, 2016) ........................................... 4 Figure 3 The geomorphically effective flow range (PWA 2009) ......................................... 10 Figure 4 Bedload rating curve and trend for Flanders. ..................................................... A-2 Figure 5 De-trended bedload rating curve. ....................................................................... A-3 Figure 6 Normal distribution showing area under curve (e.g., probability) for values

below 0.5. ............................................................................................................ A-3 Figure 7 Standardized residuals for the Flanders bedload rating curve data. .................. A-4 Figure 8 Sediment work curve and flow threshold example. ............................................ A-5 Figure 9 Illustration of spliced flow data. ........................................................................... A-7 Figure 10 Illustration of sediment load binning for computation flow thresholds. ............... A-8 Figure 11 Bedload rating curve for MEDIUM/cobble-bed channels. .................................. B-2 Figure 12 Bedload rating curve for MEDIUM/cobble-bed channels using a log-log

plot. ...................................................................................................................... B-2 Figure 13 Bedload rating curve for HIGH/sand-bed channels. ........................................... B-3 Figure 14 Bedload rating curve for HIGH/sand-bed channels using a log-log plot. ........... B-3 Figure 15 Suspended load rating curve for MEDIUM/cobble-bed channels. ..................... B-4 Figure 16 Suspended load rating curve for MEDIUM/cobble-bed channels using a

log-log plot. .......................................................................................................... B-4 Figure 17 Suspended Load Rating for HIGH/sand-bed channels. ..................................... B-5 Figure 18 Suspended Load Rating for HIGH/sand-bed channels using a log-log

plot. ...................................................................................................................... B-5 Figure 19 Flanders work curve for February 27, 2012. ....................................................... C-2 Figure 20 Flanders work curve for March 17, 2012. ........................................................... C-2 Figure 21 Flanders work curve for April 13, 2012. .............................................................. C-3 Figure 22 Flanders work curve for December 13, 2012. .................................................... C-3 Figure 23 Flanders work curve for January 25, 2013. ........................................................ C-4 Figure 24 Flanders work curve for February 19, 2013. ....................................................... C-4 Figure 25 Flanders work curve for March 8, 2013. ............................................................. C-5 Figure 26 Saratoga work curve for February 27, 2012. ...................................................... C-6 Figure 27 Saratoga work curve for March 17, 2012. .......................................................... C-6 Figure 28 Saratoga work curve for March 25, 2012. .......................................................... C-7 Figure 29 Saratoga work curve for December 13, 2012. .................................................... C-7 Figure 30 Saratoga work curve for January 25, 2013. ........................................................ C-8 Figure 31 Saratoga work curve for February 8, 2013. ........................................................ C-8 Figure 32 Saratoga work curve for March 8, 2013. ............................................................ C-9 Figure 33 Saratoga work curve for October 29, 2013. ........................................................ C-9 Figure 34 Saratoga work curve for December 7, 2013. .................................................... C-10 Figure 35 Saratoga work curve for December 19, 2013. .................................................. C-10 Figure 36 Saratoga Work Curve for March 11, 2016 ........................................................ C-11 Figure 37 Bear Valley work curve for December 13, 2012. .............................................. C-12 Figure 38 Bear Valley work curve for March 8, 2013. ....................................................... C-12

San Diego HMP – 2016 Data Analysis Update ii ESA / 140075.07 Technical Report September 2016

Table of Contents

Page

List of Figures (continued) Figure 39 Bear Valley work curve for February 28, 2014. ................................................ C-13 Figure 40 Bear Valley work curve for December 2, 2014. ................................................ C-13 Figure 41 Bear Valley work curve for December 12, 2014. .............................................. C-14 Figure 42 Bear Valley work curve for December 17, 2014. .............................................. C-14 Figure 43 Bear Valley work curve for March 1, 2015. ....................................................... C-15 Figure 44 Bear Valley work curve for January 6, 2016 ..................................................... C-15 Figure 45 Bear Valley work curve for March 11, 2016 ...................................................... C-16 Figure 46 MDS work curves for February 28, 2014. ......................................................... C-17 Figure 47 MDS work curves for December 17, 2014. ....................................................... C-17 Figure 48 MDS work curves for March 2, 2015. ............................................................... C-18 Figure 49 MDS work curves for March 7, 2016 ................................................................ C-18 Figure 50 Otay Village work curves for December 12, 2014. ........................................... C-19 Figure 51 Otay Village work curves for December 17, 2014. ........................................... C-19 Figure 52 Schoolhouse work curve for March 11, 2016 ................................................... C-20 Figure 53 Deer Valley Work Curves for January 7, 2016 ................................................. C-21 Figure 54 Best-fit cumulative work curves for bedload transport using a 95%

threshold............................................................................................................ C-21 Figure 55 Flow Peak Attenuation for DC-11 BMP Site– 2015-2016 Wet Season ................ 16 Figure 56 Flow Duration Curve for DC-11 BMP Site – 2015-2016 Wet Season .................. 16 Figure 57 Monitored Hydrographs for DC-11 BMP Site – November 2015 ......................... 17 Figure 58 Otay Village cross section. .................................................................................. D-2 Figure 59 Otay Village longitudinal profile. ......................................................................... D-2 Figure 60 Bear Valley cross section. ................................................................................... D-3 Figure 61 Bear Valley longitudinal profile. .......................................................................... D-3 Figure 62 MDS channel cross section. ............................................................................... D-4 Figure 63 MDS longitudinal profile ...................................................................................... D-4 Figure 64 Deer Valley cross section. .................................................................................. D-5 Figure 65 Deer Valley longitudinal profile. .......................................................................... D-5 Figure 66 Sycamore Canyon cross section. ....................................................................... D-6 Figure 67 Sycamore Canyon channel profile. ..................................................................... D-6 Figure 68 Ramona Grasslands cross section ..................................................................... D-7 Figure 69 Ramona Grasslands longitudinal profile ............................................................. D-7 Figure 70 Schoolhouse Canyon cross section.................................................................... D-8 Figure 71 Schoolhouse Canyon longitudinal profile. .......................................................... D-8 Figure 72 Flanders Canyon cross section. ......................................................................... D-9 Figure 73 Flanders Canyon longitudinal profile .................................................................. D-9 Figure 74 Saratoga cross section. .................................................................................... D-10 Figure 75 Saratoga longitudinal profile. ............................................................................ D-10 Figure 76 MDS Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-11 Figure 77 MDS Site Initial and 2016 Survey Left Bank and Right Bank Comparison

Photos ............................................................................................................... D-12 Figure 78 Bear Valley Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-13 Figure 79 Bear Valley Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-14 Figure 80 Deer Valley Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-15

San Diego HMP – 2016 Data Analysis Update iii ESA / 140075.07 Technical Report September 2016

Table of Contents

Page

List of Figures (continued) Figure 81 Deer Valley Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-16 Figure 82 Flanders Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-17 Figure 83 Flanders Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-18 Figure 84 Ramona Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-19 Figure 85 Ramona Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-20 Figure 86 Saratoga Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-21 Figure 87 Saratoga Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-22 Figure 88 Schoolhouse Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-23 Figure 89 Schoolhouse Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-24 Figure 90 Sycamore Site Initial and 2016 Survey Downstream and Upstream

Comparison Photos .......................................................................................... D-25 Figure 91 Sycamore Site Initial and 2016 Survey Left Bank and Right Bank

Comparison Photos .......................................................................................... D-26

List of Tables Table 1 Receiving Channel Monitoring Sites ............................................................................ 3 Table 2 BMP Monitoring Site ..................................................................................................... 5 Table 3 2012 Wet Season Monitoring Events (Adapted from Weston, 2012a) ........................ 6 Table 4 2013 Wet Season Monitoring Events (Adapted from Weston, 2013) .......................... 6 Table 5 2014 Wet Season Monitoring Events (Adapted from Weston, 2014) .......................... 7 Table 6 2015 Wet Season Monitoring Events (Adapted from Weston, 2015) .......................... 7 Table 7 2016 Wet Season Monitoring Events (Adapted from Weston, 2016) .......................... 8 Table 8 Summary of Monitoring Events and Total Samples (Adapted from Weston,

2016). ...................................................................................................................... 8 Table 9 Comparison of Peak Discharge Estimates for Pre-Development Conditions ............ 11 Table 10 Results of Visual Inflection Analysis ......................................................................... 11 Table 11 Sediment Transport Rating Curve Trend Equations ................................................ 12 Table 12 Results of De-Trended Inflection Analysis ............................................................... 13 Table 13 Comparison of low Thresholds for Bedload Transport Suggested by

Different Analysis Methods ................................................................................... 13 Table 15 Summary of Revised Geomorphic Assessments for Monitoring Sites .................... 19 Table 16 Comparison of Average Longitudinal Profile Slopes................................................ 24 Table 17 Summary of Channel Changes Inferred from Survey* ............................................. 25 Table 18 Limits of Detection (LOD) Analysis from the 2015 Receiving Channel

Surveys ................................................................................................................. 25 Table 19 Interpretation of Hypothetical Monitoring Results .................................................... 26

San Diego HMP – 2016 Data Analysis Update iv ESA / 140075.07 Technical Report September 2016

I. Introduction The County of San Diego and Municipal Copermittees have initiated a long-term monitoring project to assess the effectiveness of their Hydromodification Management Plan (HMP) (Brown and Caldwell, 2011). The Copermittees defined an effective plan as one that ensures compliance with HMP design criteria, and results in no significant stream degradation due to increased erosive force caused by new development. The plan presented three questions to assess the effectiveness of monitoring activities:

1. Do field observations confirm that the HMP appropriately defines the flow rate (expressed as a function of the 2-year runoff event) that initiates movement of receiving channel bed or bank materials?

2. Are hydromodification mitigation facilities (flow-control BMPs) adequately meeting the flow duration design criteria outlined in the HMP?

3. What is the effect of development on the cross-sectional stability of downstream receiving channels?

This report evaluates these three questions with data collected over 5 years from the 2011-2012 to the 2015-2016 wet-weather monitoring season. This report is organized as follows. First, a background of the HMP is presented. Next, the approach, methods, and results are discussed for each monitoring question. Finally, overall conclusions related to the effectiveness of the HMP are made.

II. HMP Monitoring Background ESA and Weston Solutions (Weston) have been contracted by the County to help develop and implement a monitoring project that addresses the core questions listed above. The project has been divided into three phases, which are being implemented over a 5-year period (Figure 1). Phase I of the project began in 2011 with a focus on developing standardized protocols for receiving channel surveys, geomorphic assessments, and in-stream monitoring of water and sediment. Phase I protocols were applied to an initial set of reference (undeveloped) and urban (developed prior to HMP implementation) monitoring sites during a portion of the 2012 wet season (February to April). Phase II began during the second half of 2012 with the goal of adding development sites to wet season monitoring. Development sites are sites that are currently undeveloped but where development plans have been submitted, and where development will comply with the HMP runoff requirements. Two development sites were added and monitored during the 2013 wet season. An additional development site was added and monitored during the 2014 wet season. The third and final phase of the project began in 2015 with expanded monitoring to include the continuous monitoring of constructed BMPs. Together these monitoring activities will collect the necessary data to assess the effectiveness of the HMP.

ESA was also tasked to analyze all in-stream monitoring data collected by Weston. The primary goal of this analysis was to assess if the monitoring data supports the use of the low-flow thresholds currently assigned to different channel types and associated susceptibility ratings (e.g., HIGH, MEDIUM, or LOW susceptibility to hydromodification). Since low-flow thresholds were developed using a large sensitivity analysis of hypothetical data, it is important to supplement these data with field observations. Others goals of this report are assessing the effectiveness of

San Diego HMP – 2016 Data Analysis Update 1 ESA / 140075.07 Technical Report September 2016

2016 Data Analysis Report

flow-control BMPs in mitigating post-development flow frequencies and durations, and assessing the role of development on the geomorphic stability of receiving channel monitoring sites. These datasets will be used to validate or revise the existing low-flow thresholds and BMP flow duration design criteria at the end of the current HMP planning cycle. A summary of the 5 years of data that is the basis for this analysis is presented in the Effectiveness Assessment Monitoring for the San Diego Hydromodification Management Plan Draft Wet Weather Event Monitoring Report (Weston, 2016).

Figure 1. Phased monitoring approach (Source: Weston, 2014)

A. Low-Flow Thresholds The evaluation of increased erosive force resulting from hydromodification has been limited to the geomorphically effective flow range, which is defined between the flow associated with the minimum or critical shear stress required to erode channel materials (low-flow threshold) and the 10-year flow event (Q10). The HMP requires the use of two assessment tools to determine the low-flow threshold of receiving channels downstream of BMP outfalls:

• Hydromodification Screening Tools (Bledsoe et al., 2010)

• Low Flow Calculator (Brown and Caldwell, 2011)

These tools are based on a variety of channel and valley measurements and observations including bed and bank materials, channel slope, channel cross section, and stream assessment characteristics. Both tools rate the overall susceptibility to channel erosion, and assign a low-flow threshold as a function of the 2-year flow event (Q2):

• 0.1 Q2 for streams with HIGH susceptibility to channel erosion



• 0.3 Q2 for streams with MEDIUM susceptibility to channel erosion

• 0.5 Q2 for streams with LOW susceptibility to channel erosion

The final susceptibility rating and low-flow threshold assigned to a receiving channel is determined from the more conservative of the two methods. For instance, if the low-flow calculator assigned a LOW rating and the screening tools assigned a MEDIUM rating, a MEDIUM rating would be given to the receiving channel. In this example, hydromodification facilities would be designed to mitigate for flow events ranging from 0.3Q2 to Q10.

B. Receiving Channel Monitoring Sites A total of nine receiving channels were secured and instrumented for in-stream monitoring (Table 1; ESA PWA, 2013). Each monitoring site consists of a monumented cross section for repeat channel surveys and event-based monitoring, mounting brackets for continuous flow monitoring equipment, and a nearby rain gauge (Weston, 2004). In order to assess the potential effects of hydromodification on receiving channels and the performance of HMP mitigation facilities, monitoring sites were selected to represent three site categories:

• Development Sites – receiving channels located downstream of hydromodification BMP outfalls from future development projects located in the upper watershed

• Reference Sites – channel cross sections selected within relatively undeveloped watersheds in the upper watershed

• Urban Sites – receiving channels downstream of existing development in the middle watershed that were developed prior to the HMP

Monitoring sites were selected to focus on more susceptible stream types, MEDIUM and HIGH, since these are the most common in the San Diego region. Care was given to select monitoring sites that encompass a broad geographic area and a range of watershed and receiving channel conditions (Figure 2).

TABLE 1 RECEIVING CHANNEL MONITORING SITES

Site ID Site Name Site Category Stream

Susceptibility Latitude Longitude

DH-1 Otay Village Development HIGH 32.64217 -116.92511

DH-2 Bear Valley Development HIGH 33.11485 -117.04931

DH-3 MDS Development HIGH 33.08174 -116.84089

RM-1 Deer Valley Reference MEDIUM 32.95088 -117.17713

RM-2 Sycamore Canyon Reference MEDIUM 32.9328 -116.97459

RH-1 Ramona Reference HIGH 33.04594 -116.95177

RH-2 Schoolhouse Canyon Reference HIGH 33.08438 -116.94512

UM-1 Flanders Canyon Urban MEDIUM 32.8987 -117.17432

UH-1 Saratoga Urban HIGH 33.08584 -117.06191



Figure 2. Overview of monitoring sites (Source: Weston, 2016)



C. BMP Monitoring Sites At the time of this report, one BMP location had been selected and instrumented for continuous monitoring; Figure 2). This BMP monitoring site is “decoupled” from the receiving channel monitoring site, in other words, the BMP is not part of the three Development Sites selected for in-stream monitoring. Decoupling of BMP monitoring from receiving channel monitored was a key recommendation during the 2013 re-evaluation of the HMP Chapter 8 Monitoring Plan due to delayed construction schedules at the Development Sites and the programmatic need to assess BMP flow frequency and duration performance as part of the effectiveness assessment (ESA PWA and Weston, 2013).

TABLE 2 BMP MONITORING SITE

Site ID Site Description Nearby Place

Name Monitoring

Status Latitude Longitude

DC-11 Residential Development Scripps Ranch Active 32.905578 -117.07235

III. Question 1 – Validity of Low-Flow Thresholds

A. Approach The low-flow thresholds, as estimated using the HMP tools, are considered valid if they match the observed flow at which significant amounts of sediment become entrained and transported. HMP thresholds below the observed threshold of significant erosion would be over-conservative and unnecessarily burdensome on developers, while HMP thresholds above this point would be under-protective of the receiving channel. To evaluate the low-flow thresholds, a two-pronged approach was used. First, rating curves of observed water and sediment discharge in test channels were qualitatively analyzed for inflections where the rate of sediment transport greatly increased with a small increase in flow. The basis behind this test is that inflections where sediment discharge changes more rapidly than water discharge can be an indicator of higher-intensity sediment transport modes. Second, event-based work curves were produced that estimate how much sediment transport occurs between the lower and upper flow thresholds. To put these results in the context of the 2-year flow, it was necessary to develop an estimate of the 2-year flow event for each receiving channel. Because no long-term flow data has been collected at any of the monitoring sites, the 2-year flow event was estimated using the 2012 U.S. Geological Survey (USGS) regression equations for the South Coast hydrologic region (Section III.C).

The (2012) 2-year flow regional regression equation develop by the USGS is represented by two variables, drainage area and mean annual precipitation as well as two regression coefficients. The development of the 2-year returns period flows for the HMP Effectiveness Assessment utilized the United States Department of Agriculture (USDA) PRISM data source, the same source of precipitation as the original regression equation development by the USGS. PRISM is a set of monthly, yearly, and single-event gridded data products of mean precipitation, In-situ point measurements are ingested into the PRISM (Parameter elevation Regression on Independent Slopes Model) statistical mapping system. The PRISM products use a weighted regression scheme to account for complex climate regimes associated with orography, rain shadows,



temperature inversions, slope aspect, coastal proximity, and other factors. PRISM is the USDA's official climatological data (NCARS, 2015).

B. Data Collection To date, five sets of in-stream monitoring data have been collected to validate the low-flow threshold of the receiving channel monitoring sites. The first set of monitoring data was collected at four sites by Weston during a portion of the 2012 wet season (February–April, 2012; Table 3). The second set of monitoring data was collected at six sites over the 2013 wet season (December 2012–March 2013; Table 4). The third set of monitoring data was collected at seven sites over the 2014 wet season (October 2013–March 2014; Table 5). The fourth set of monitoring data was collected at seven sites over the 2015 wet season (December 2014–March 2015; Table 6). Further, a fifth set of monitoring data was collected at nine sites over the 2016 wet season (December 2015–March 2016; Table 7). The most recent summary of wet-weather monitoring data is provided in the Effectiveness Assessment Monitoring for the San Diego Hydromodification Management Plan Draft Wet Weather Event Monitoring Report (Weston, 2016).

TABLE 3 2012 WET SEASON MONITORING EVENTS (ADAPTED FROM WESTON, 2012A)

Site Name

Monitoring Event Dates (site event rainfall totals in parenthesis)

2/27/2012 3/17/2012 3/27/2012 4/13/2012

Deer Valley No Flow* (0.47”)

No Flow* (0.52”)

NS No Flow* (0.81”)

Ramona NA No Flow* (1.83”)

NS No Flow* (0.88”)

Flanders Sampled (0.66”)

Sampled (0.60”)

NS Sampled (0.44”)

Saratoga Sampled ( 0.80”)

Sampled (2.00”)

Sampled (0.93”)

NA

* - Site was visited during storm event and no flow was observed or measured with level loggers NS - Not sampled (storm event did not meet site-specific mobilization criteria) NA - Not applicable

TABLE 4 2013 WET SEASON MONITORING EVENTS (ADAPTED FROM WESTON, 2013)

Site Name


12/13/2013 1/25/2013 2/8/2013 2/19/2013 3/8/2013

Otay Village NS NS NS NS Sampled (0.96")

Bear Valley Sampled (1.63")

NA NA NS Sampled (1.32")

Deer Valley NS NS NS NS NS



Ramona NS NS NS NS NS

Saratoga Sampled (1.63")

Sampled (0.64")

Sampled (0.19")

NS Sampled (1.32")

Flanders Sampled (1.84")

Sampled (0.79")

NS Sampled (0.45")

Sampled (1.81")


Site Name


10/9/2013 10/28/2013 11/21/2013 12/7/2013 12/19/2013 2/28/2014 3/1/2014

Otay Village NS NS NS NS Sampled (0.96")

NS Sampled (0.96")

Bear Valley NS NS NS NS Sampled (1.32")

Sampled (1.13")

NS

MDS NS NS NS NS NS Sampled (2.15")

NS

Deer Valley NS NS NS NS NS NS NS

Ramona NS NS NS NS NS NS NSs

Flanders NS NS NS NS Sampled (1.81")

NS NS

Saratoga NS Sampled (0.49")

NS Sampled (0.22")

Sampled (0.03")

NS NS


Site Name


12/2/2014 12/12/2014 12/16/2015 12/17/2015 3/1/2015 3/2/2015

Otay Village NS Sampled (0.78")

NS Sampled (0.58")

NS NS

Bear Valley Sampled (0.69") Sampled (0.86")

NS Sampled (0.37")

Sampled (0.63")

NS

MDS NS NS NS Sampled (0.71")

Sampled (0.98")

NS

Deer Valley NS NS NS NS NS NS

Ramona NS NS NS NS NS NS

Flanders NS NS NS NS NS NS

Saratoga NS NS NS NS NS NS




Site Name


01/06/2016 01/07/2016 03/06/2016 03/11/2016

Otay Village NS NS NS NS

Bear Valley Sampled (0.99") NS NS Sampled (0.21)

MDS NS NS Sampled (0.96)

NS

Deer Valley NS Sampled (0.98)

NS NS

Ramona NS NS NS NS

Flanders NS NS NS NS

Saratoga NS NS NS Sampled (0.23)

Schoolhouse Canyon NS Sampled (0.63)

NS NS

Stream stage (depth), velocity, turbidity, suspended sediment, and bedload were sampled at each of the monitoring sites where field conditions were supportive (Table 8). Prior to the 2016 wet weather season, none of the rainfall events during the previous 4 years of monitoring generated runoff within the Reference Site channels. The absence of runoff for these previous rainfall events provides insight into predevelopment conditions. Runoff was observed at developed sites. Standardized protocols for these monitoring activities are outlined in the working draft of the Detailed Monitoring Plan (Weston and ESA, 2015) and the companion Quality Assurance Project Plan (Weston, 2012b).

TABLE 8 SUMMARY OF MONITORING EVENTS AND TOTAL SAMPLES (ADAPTED FROM WESTON, 2016).

Site ID Site Name Site Category Stream Susceptibility No. of Storms

Monitoring No. of Samples

DH-1 Otay Village Development High 4 32 DH-2 Bear Valley Parkway Development High 9 98 DH-3 MDS Development Development High 4 22 RM-2 Sycamore Canyon Reference Medium 1 0* RH-2 Schoolhouse Canyon Reference High 2 6 RM-1 Deer Valley Reference Medium 4 10 RH-1 Ramona Reference High 2 0* UM-2 Flanders Urban Medium 7 55 UH-1 Saratoga Urban High 11 79 *- Flows were observed and recorded at all reference sites during the 2016 Wet Season. Prior to 2016, no flows were observed at these reference sites. Deer Valley and Schoolhouse met the criteria to mobilize and samples were collected at both of these sites in 2016



C. Data Analysis

i. Peak Discharge Estimates Because no long-term flow data has been collected at any of the receiving channel monitoring sites, the 2-year and 10-year peak-flow events were estimated using two sets of regression equations, specifically the USGS equations for the South Coast hydrologic region (Gotvald et al., 2012) and those developed and calibrated by Hawley and Bledsoe (2011) for Southern California watersheds. Preliminary results of a recent hydrologic model calibration study for the San Diego region has shown that the 2012 USGS equations are generally good predictors of peak-flow events in small headwater channels, and may actually outperform uncalibrated continuous simulation rainfall-runoff models (SDSU, 2015). For the current data analysis update, the USGS equations were used to estimate the frequency, or “return interval,” of each flow event.

ii. Rating Curve Analysis Rating curves showing discharge and sediment load were developed to analyze the relationship between the two parameters, and to identify the minimum discharge as a function of the 2-year flow event required to mobilize bed sediments. For comparison purposes, rating curves for suspended load and bedload were developed for all monitoring sites using 2012–2016 data. Rating curves have been binned into HIGH and MEDIUM channel susceptibility. Sediment load data for Otay Village has been plotted on both MEDIUM and HIGH susceptibility figures, since it has characteristics of both susceptibility types (e.g., channel bed contains considerable cobble, which is normally associated with MEDIUM channels, but the channel is rated HIGH due to incised form and relatively steep bed slope).

Two different tests were used to evaluate the rating curve data for the low-flow threshold. First, data were visually analyzed for deviations in bedload transport that show the flow where the rate of change of sediment transport increased sharply. Second, the rating curves were quantitatively analyzed by de-trending each rating curve and looking for statistical outliers. To do this, a trend was fit to each rating curve for both bedload and suspended load. Power equations were used as trends due to their almost ubiquitous use for sediment transport rating curves within the field of geomorphology. Next, the trend was subtracted from the data and the residuals were standardized by the mean and standard deviation. This standardized data can then be assessed in terms of Z-scores, where 1 standard deviation is equal to a value of 1, while 2 standard deviations are equal to a value of 2, etc. Statistical significance was assessed in this test at a value of 0.5 (0.5 standard deviation). As more data becomes available this criteria could be strengthened. Further, because this analysis is concerned with positive rates of change in sediment transport, only positive outliers were assessed. Thus, the low-flow threshold was evaluated as positive values greater than 0.5 of the de-trended and standardized data. An example of this de-trending analysis has been included in Appendix A.

iii. Event-based Work Curves ESA has developed an automated tool in MATLAB to translate sediment and flow data into work curves relating sediment transport rates to a series of flow thresholds for monitoring sites. The two primary inputs to the tool are flow frequency relationships for the creek, used to set the thresholds between which total bedload and suspended load transport is computed, and a time series of flow and sediment data collected for a measured runoff event. Flow frequency values of 0.1Q2, 0.3Q2, 0.5Q2, and Q10 were used as computational flow thresholds. The goal of the event-



based work curve analysis was to determine what proportion of sediment load for each rainfall-runoff event was transported above each flow threshold.

Previous HMP studies (e.g., those for Santa Clara County and the Newhall Ranch development in Los Angeles County) have shown that the majority of the long-term cumulative sediment load for various channel types is transported between some proportion of the 2-year flow event and the 10-year flow event (Figure 3). Flows less than some proportion of the Q2 event happen frequently, but may not generate enough erosive force to mobilize significant sediment load. The proportion of Q2 required to mobilize significant sediment load is dependent on the size and distribution of channel sediments. As previously discussed in Section II.A, this is the basis for the existing low-flow thresholds. Flows greater than the Q10 event are capable of transporting large sediment loads, but by definition these happen less frequently. For the purposes of the event-based work curve analysis, it was assumed that a 95% cumulative sediment load would be adequate to emulate the geomorphically effective flow range. A visual representation of the thresholds concept and details of the inputs, outputs, and computational process has been provided in Appendix A.

Figure 3. The geomorphically effective flow range (PWA 2009)

D. Results and Discussion

i. Peak Discharge Estimates The 2-year and 10-year peak-flow estimates for each receiving channel monitoring sites are shown in Table 9. The variation in drainage area and mean annual precipitation between the contributing watersheds leads to a wide range of discharge. Overall, the Hawley and Bledsoe estimates are lower than the USGS estimates for the 2-year event, but greater for the 10-year event. The USGS equations were used for all flow estimates in the remainder of this report.



TABLE 9 COMPARISON OF PEAK DISCHARGE ESTIMATES FOR PRE-DEVELOPMENT CONDITIONS

Site ID Site Name Drainage Area (mi2)

Mean Annual Precipitation (in)

USGS (2012) Hawley & Bledsoe

(2011)*

Q2 (cfs)

Q10 (cfs)

Q2 (cfs) Q10 (cfs)

DH-1 Otay Village 0.60 14.0 19 74 11 88

DH-2 Bear Valley 0.30 15.7 13 49 8 53

DH-3 MDS 0.17 18.8 10 37 7 36

RM-1 Deer Valley 0.10 12.4 5 16 3 17

RM-2 Sycamore 0.70 16.8 24 102 16 116

RH-1 Ramona 0.10 17.3 7 23 4 22

RH-2 Schoolhouse 0.80 16.8 26 113 17 130

UM-1 Flanders 1.9 12.5 37 162 21 220

UH-1 Saratoga 0.80 15.6 25 104 16 123 * - Using 0 percent imperviousness to emulate pre-development conditions.

ii. Rating Curve Analysis For reference, figures showing rating curves for all receiving channel monitoring sites have been provided in Appendix B. The results for the visual inflection analysis are summarized in Table 10. The bedload rating curve for Flanders Canyon, a MEDIUM susceptibility channel, shows that rates of sediment transport begin to increase more rapidly at approximately 1.2Q2 (Figure 11). For the HIGH susceptibility and/or sand-bed channels, bedload transport begins to increase more rapidly with discharge at approximately 0.1-0.2Q2 (Figure 13). Limited bedload data has been collected at Otay Village, MDS, Schoolhouse, and Deer Valley, and visual inflection curves are inconclusive.

TABLE 10 RESULTS OF VISUAL INFLECTION ANALYSIS

Site Name Stream

Susceptibility Bed

Material

Inflection (Q/Q2)

Bedload Suspended Load

Flanders Canyon MEDIUM Cobble 1.2 0.3

Saratoga HIGH Sand 0.1 0.1

Bear Valley HIGH Sand 0.1 0.03

MDS HIGH Sand * *

Otay Village HIGH Cobble * *

Deer Valley MEDIUM Cobble * *

Schoolhouse HIGH Sand * *

* - Unable to detect due to sample size and range of data



Visual inflection points were less defined for suspended load data across sites. The suspended load rating curve for Flanders Canyon (Medium/cobble), shows that suspended load may begin to increase more rapidly at approximately 0.3Q2 (Figure 15). Rating curves for HIGH susceptibility and/or sand-bed channels suggest that suspended load may begin to increase more rapidly with discharge at approximately 0.1Q2 (Figure 17). Suspended sediment ratings curves for Otay Village and MDS span a relative small range of flow events, and the visual inflection curves are inconclusive (Figures 15–18).

The trend equations used for the second inflection test are shown in Table 11. As can be expected, better fits are found for data sets with higher sample sizes.

TABLE 11 SEDIMENT TRANSPORT RATING CURVE TREND EQUATIONS

Site Name Sample Size Bedload Suspended Load

Equation R² Equation R²

Flanders Canyon 47 y = 4.0185x2.989 0.8765 y = 99.293x0.6812 0.8765

Saratoga 76 y = 221.25x1.4596 0.5047 y = 526.24x0.8155 0.5818

Bear Valley 96 y = 12.803x1.0749 0.4689 y = 403.5x0.295 0.2195

MDS 18 y = 3.4489x0.6673 0.2583 y = 7624.4x0.2671 0.2845

Otay Village 14 y = 0.0002x-0.579 0.1582 y = 1107.1x0.3187 0.2089

Deer Valley 10 y = 0.0011x-0.054 0.0004 y = 1399.7x1.0856 0.5871

Schoolhouse 6 * * * *

*Limited sample size – no trend determined

The results for the de-trended inflection analysis are shown in iii. Event-based Work Curves.

iii. Event-based Work Curves Cumulative bedload and suspended load were computed for all data collected prior to this report using the automated procedure developed for this analysis. The work curves relating bedload and suspended load transported for each storm event are provided in Appendix C (Figures 19–53).

iv. Comparison of Results As shown in Table 12, Flanders had de-trended inflections at 1.2Q2 for both bedload and suspended load. Saratoga showed the most variability between the inflection discharge for bedload and suspended load, with values of 0.1 and 0.5 Q2, respectively. Bear Valley was more consistent between the two, with values between 0.1 and 0.2 Q2. As discussed previously, MDS, Otay, Deer Valley, and Schoolhouse could not be assessed because of the lack of data.



TABLE 12 RESULTS OF DE-TRENDED INFLECTION ANALYSIS

Site Name

Discharge Inflection as a Function of USGS Q2

Bedload Suspended Load**

Flanders 1.2 1.2

Saratoga 0.1 0.5

Bear Valley 0.1 0.2

MDS * *

Otay * *

Deer Valley * *

Schoolhouse * *

*- Unable to detect based on sample size and range of data **Average values provided due to hysteresis

Table 13 presents a summary of results from the work curve analysis and comparisons with the two inflection methods for bedload sediment transport. Using a 95% cumulative sediment load to emulate the effective flow range (see Appendix C -Figure 54), the current low-flow thresholds are well supported. In general, the two inflection analyses show similar low-flow thresholds. Further, with the exception of Flanders, all methods suggest similar low-flow thresholds for individual sites. The lower cumulative sediment transport rate for Bear Valley (0.02Q2) is likely due to incision and widening of the channel reach upstream of the monitoring site.

TABLE 13 COMPARISON OF LOW THRESHOLDS FOR BEDLOAD TRANSPORT SUGGESTED BY DIFFERENT ANALYSIS

METHODS

Site Name / Analysis Method

Low-Flow Threshold (Proportion of Q2)

Stream Susceptibility Rating

Visual Inflections

De-Trended Inflections

Work Curves

Flanders 1.2 1.2 0.35 0.3

Saratoga 0.1 0.1 0.1 0.1

Bear 0.1 0.1 0.03 0.1

MDS * * * 0.1

Otay * * * 0.1

Deer Valley * * * 0.3

Schoolhouse * * * 0.1

* - Not enough data collected to conduct rating curve analysis



IV. Question 2 – Performance of Flow-Control BMPs The planned approach to address this question was to compare flow duration and frequency estimates from observed data with values derived from models for hydromodification mitigation facilities or flow-control BMPs to determine if the facilities are reducing the post-project peak flow frequency and duration to pre-project levels. The planned analysis was to be based on data from selected construction sites over a period of several years. During initial development of the HMP, monitoring plan, it was envisaged that BMP monitoring would be “coupled” to channel monitoring (BMPs would be monitored in a new development that drained to a channel that was also monitored for geomorphic response). However, the slow pace of site construction within the County during the first few years of the monitoring period, and the need to commence channel monitoring, made coupling sites impossible. The flow-control BMPs coupled with the Development Sites used for in-stream monitoring were not constructed during the 5-year study, and therefore, the flow-control BMPs for those developments were not monitored. Decoupling of BMP monitoring from receiving channel monitored was a key recommendation during the 2013 re-evaluation of the Chapter 8 monitoring plan that was presented in the Technical Report provided as Attachment 1 of Exhibit A of this report (ESA PWA and Weston, 2013). One “decoupled” BMP location was subsequently instrumented for continuous monitoring during the 2015–2016 wet weather season to allow for collection of performance-based flow frequency and duration data within the 5-year study.

A. Approach Flow-control BMP monitoring was used to assess accuracy of existing hydrologic models using the precise continuous flow measurements for each of the BMP inflow and outflow locations. Design criteria based on deviation from predevelopment hydrology was then analyzed to recommend changes to more closely match the post-project flow curves to the pre-project condition. These data can also be used to analyze the precision of HMP sizing factors and extended detention facility design criteria and to potentially recommend changes to more closely match the mitigated post-project curves to pre-project condition, peak flow frequency, and flow duration curves

B. Data Collection Wet weather monitoring included flow-control BMP monitoring at the one BMP site (DC-11). During the 2015–2016 wet weather season, monitoring activities included continuous monitoring of precipitation, stage, area and velocity of inflows and outflow, and event-based monitoring of BMP components to validate continuous monitoring. Wet-weather cross-sectional flow measurements were used to develop precise flow rating curves for each of the BMP inflow continuous flow-monitoring locations.

C. Data Analysis The DC-11 BMP site was instrumented for continuous monitoring to allow for collection of performance-based flow frequency and duration data within the 5-year study. Flow-control BMP monitoring activities included continuous monitoring of precipitation, stage, area and velocity of inflows and outflow, and event-based monitoring of BMP components to validate continuous monitoring. The continuous flow monitoring equipment was used to quantify stormwater flows into the BMP from the two tributary drainage areas, water levels in the bioretention basin, and



discharge from the BMP. During the 2015-2016 wet weather season, stream ratings were collected over the course of two storm events to develop precise flow rating curves for each of the BMP inflow continuous flow monitoring locations. During the January 2016 storm event, intense rainfall (peak intensity of 1.22 inches per hour) caused the bioretention basin to rapidly fill and begin bypassing peak storm flows. Note that this event exceeds the upper flow duration control threshold (Q10) for HMP BMPs.

Depending on how events are grouped or divided, twelve runoff events were monitored in the 2015-16 wet weather period, of which ten had inflows exceeding 0.13 cfs (the estimated 0.1Q2 for the watershed draining to the DC-11 BMP Site).

An example of the flow data collected during the 2015-2016 wet weather season is summarized in Table 14.

TABLE 14. BMP SITE DC-11 PERFORMANCE DURING THE 2015-2016 WET WEATHER SEASON

D. Results and Discussion The measured inflows and outflows are shown in Figures 55. The BMP inflows and outflows show that for these events significant peak flow attenuation occurred, as intended. The average peak inflow (all twelve events) was 2.0 cfs while the average peak outflow was 0.3 cfs. Plotting the continuous measurements as a flow duration curve (Figure 56) shows that the duration of flow at the Q2 threshold, 1.3 cfs (considered to be the dominant flow for Southern California receiving waters), was reduced from 0.17% to 0.07%,. The twelve events monitored show the BMP working well to prevent hydromodification across a wide range of geomorphically-significant conditions.



Figure 55, Flow Peak Attenuation for DC-11 BMP Site – 2015-2016 Wet Season

Figure 56, Flow Duration Curve for DC-11 BMP Site – 2015-2016 Wet Season

The hydrograph for a representative week of monitored data shows attenuation of peak flows (Figure 57). The small event of November 23rd shows BMP outflow exceeding total BMP inflows. A compacted dirt lot between the BMP swales drains directly into the retention basin and can contribute to the inflow but is not monitored.

0

1

2

3

4

5

6

0 1 2 3 4 5

BMP

Out

lfow

Pea

ks(c

fs)

BMP Sum of Inflow Peaks (cfs)

MeasuredEvents

No BMP,Inflow=Outflow0.1 Q2

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

0 20 40 60 80 100

Flow

(cfs

)

Percent Time Exceeding Flow

Inflow

Outflow



Figure 57, Monitored Hydrographs for DC-11 BMP Site – November 2015

V. Question 3 – Stability of Receiving Channels

A. Approach The HMP Copermittees have monitored nine channels that are typical of non-exempt stormwater receiving channels across the county. In 2009–2010, ESA performed geomorphic assessments at a number of candidate channel sites, of which nine were subsequently selected for monitoring over a 5-year period between the 2011–2012 and the 2015–2016 winters. The geomorphic assessments followed the protocol described in Bledsoe et al. 2010 (Southern California Coastal Water Research Project Technical Report [TR] 606). The TR 606 assessments are used by land developers following the HMP requirements to classify channels into vertical and lateral erosion susceptibility classes (High, Medium, and Low susceptibility) that are then used with other tools to determine the low-flow threshold for flow duration control. The channels monitored in the HMP monitoring program were selected to represent three different land uses: reference (undeveloped watersheds); development (channels where discharge from a new development that will conform with the HMP was planned at the time monitoring commenced); urban (channels receiving stormwater from developments that took place prior to the HMP). The channels, their land uses and monitoring observations are listed in Table 15. The reason for selecting a mixture of undeveloped and developed or developing watersheds was to distinguish “signal” (e.g., erosion from stormwater runoff) from “noise” (e.g., natural levels of erosion).

In addition to the geomorphic assessments at the start and end of the 5-year monitoring period, repeated measurements of channel cross section and slope were made.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

11/18/15 11/20/15 11/22/15 11/24/15 11/26/15 11/28/15 11/30/15 12/2/15

BMP Inflows

BMP Outflow



B. Data Collection The receiving channel of each monitoring site was monumented and initially surveyed with a Total Station or RTK (real-time kinematic) unit using the protocols laid out in the Detailed Monitoring Plan (Weston and ESA, 2015). Surveys consisted of collecting cross section and long profile data. Repeat surveys with a basic level and survey rod were conducted during subsequent years after each wet weather season (typically May). The length of cross section surveys and longitudinal profiles were truncated to limit field time in subsequent surveys using the rod and level method. Upper hillslopes for cross sections tend to not change as much as the bankfull channel, justifying the reduction of cross section survey length.

Small variations in inter-annual surveys are expected. This can be due to different survey equipment used, as well as different operators. The number and spacing of survey points selected by the operator can produce variations from survey to survey even if no change has occurred. Selection of the thalweg profile in relatively flat channels can also vary with changing operators.

Additional survey protocols were implemented in 2015 to measure the limits of detection (LOD) inherent to receiving channel surveys. The LOD analysis was based on variations in elevation from variable bed sediments and survey operator error at four monitoring locations: Sycamore Canyon, Schoolhouse Canyon, Deer Valley, and Flanders Canyon. The difference between the D84 and D50 sediment size was used to define the potential difference in survey elevation due to variable sediments. Replicate cross section surveys were conducted at the four monitoring sites by reoccupying the same stations as the initial cross section. The LOD for the four monitoring locations was measured using the following formula:

𝐿𝐿𝐿𝐿𝐿𝐿 = 𝑡𝑡�(𝐸𝐸𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡1)2 + (𝐸𝐸𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡2)2

where t is the t-statistic or the ratio of departure of an estimated parameter from its notional value and standard deviation, and Etime is the total potential error associated with a given survey. This can be used to assess change at a given t value (e.g., a t value of 1.96 equates to a 95% confidence interval) or to inversely determine the t-value associated with observed change. The total potential error for each annual survey is composed of sediment variability (ztime) and average error between replicate surveys (stime):

𝐸𝐸𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡1= (𝑠𝑠𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡1 + 𝑧𝑧𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡1)

For each cross section and longitudinal profile, the LOD can be used to determine whether or not the observed change is significant relative to the background error associated with the survey and bed sediments.



TABLE 15 SUMMARY OF REVISED GEOMORPHIC ASSESSMENTS FOR MONITORING SITES

Site Name

HMP Monitoring

Type

Evidence of Erosion/

Deposition? Repeat

Assessment?

Susceptibility Class

Changed?

Notes and interpretation. Is change (if observed) indicative of instability in channel

or watershed?

Ramona Reference 2–4” of deposition in long profile. No change in cross

section.

Yes No Fine sediment from watershed has formed a thin layer on the channel bed over original bed (also

sand). Appears to be cyclical deposition, potentially sheet wash from the surrounding

former floodplain terrace, likely to be washed out in subsequent years. Site appears stable.

Deer Valley Reference Small patches of up to 6” of fine

sediment depositing in

channel

Yes Yes (Medium to

High)

Fine sediment from watershed has formed a thin layer on the channel bed (originally gravel).

Appears to be cyclical deposition, fines likely to be washed out in subsequent years. Fine

sediment has caused changed classification. Site appears stable.

Schoolhouse Reference 9–18” of fine sediment

deposition in channel

Yes No Significant fine sediment from watershed (potential fire effects). Deposition is pronounced

enough to potentially cause channel infilling/avulsion and lateral migration within the valley floor. Potentially unstable site in medium

term.

Sycamore Reference 4–6” of fine sediment

deposition in much of reach

Yes Yes (Medium to

High)

Fine sediment from watershed has formed a thin layer on the channel bed (formerly gravel).

Appears to be cyclical deposition, likely to be washed out in subsequent years. Fine sediment has caused changed classification. Site appears

stable.

Bear Valley Development Up to 9” of erosion over a short reach

Yes No Local scour set against overall influx of fine sediment (potentially from development

upstream). Possible migration of outside bend and infilling/avulsion of downstream channel.

Otay Village Development No No - -

MDS Development

Development 6-12” of upstream erosion, 6–12” of

deposition downstream

Yes No Upstream sections of channel have eroded due to watershed runoff, depositing sediment in

culvert backwater. Incision and channel widening occurring between two grade controls.

Site appears moderately unstable in medium term.

Flanders Urban ~12” of upstream erosion and downstream deposition

Yes No Gravel pulse passing through site. Cyclical deposition of intermediate size bed–lining

material, likely to be washed out in subsequent years. Site appears stable.

Saratoga Urban Upstream headcut migration and downstream deposition

Yes No Headcut migrating through reach causing upstream incision and downstream deposition.

Headcut likely to proceed until arrested by grade control. Site appears unstable.

In 2016, repeat geomorphic assessments and channel stability classifications were conducted at any sites where the survey data suggested a significant change in channel dimensions had occurred. The geomorphic assessments followed the protocol described in Bledsoe et al. 2010 (Southern California Coastal Water Research Project TR 606). The TR 606 assessments are used by land developers following the HMP requirements to classify channels into vertical and lateral



erosion susceptibility classes (High, Medium and Low susceptibility) that are then used with other tools to determine the low-flow threshold for flow duration control.

C. Data Analysis To analyze the cross section and long profile data, qualitative observations were made along with some quantitative comparisons. The qualitative observations sought to identify changes in the data sets and relate them to observations made during data collection. The quantitative comparisons consisted of comparing: (1) the vertical and/or lateral change in cross section geometry and (2) changes in the overall slope of the longitudinal profiles. For longitudinal profiles, the standard deviation was used as a simple indicator of the variability amongst years. In addition, initial LOD are provided and compared with observed inter-annual changes.

D. Results and Discussion The channels were monitored for five wet seasons to collect data on flow, sediment transport, and morphological adjustment, as part of the wider HMP monitoring program. In accordance with the HMP monitoring plan, channel sites that showed evidence of erosion or deposition based on repeat cross section and long profile surveys received repeat geomorphic assessments at the end of the 2015–16 wet season. One site that did not have change within the LOD for repeat surveys (Otay Village) was not reevaluated. At each site the TR 606 assessment was performed, cross sections and long profiles were compared with field evidence, and a brief visual reconnaissance of the channel around the site was performed to see whether there was evidence to confirm and/or account for observed changes in the channel since the start of monitoring. In particular, an attempt was made to determine whether observed changes were small-scale cyclical changes (such as deposition or scour of loose bed sediment overlaying a more resistant bed), or longer term (e.g., failing banks or active incision into the bed). A summary of prior channel surveys and key field observations is discussed in the following narrative, while supporting figures and comparison photos from the initial survey and the 2016 survey can be found in Appendix D (Figures 58–91).

i. Changes in Channel Cross Section and Profile DH-1, Otay Village – First surveyed in 2012. Subsequent surveys show some slight variations in channel cross section and profile, though no changes in channel form or stability state were observed during annual field assessments. Small variations in channel cross section are likely due survey error (e.g., selection of survey points and angle of cross section) and are not indicative of bank slumping or other lateral processes (Figure 58). The longitudinal profile indicates that some minor incision may have occurred toward the downstream end of the profile with inter-annual changes in bed elevation ranging from 0.25 to 0.5 feet (Figure 59). Average channel slope has not changed significantly since 2012. Based on 2016 survey results. there is no evidence of channel change within the LOD at this location was evident; therefore, the site was not re-evaluated.



DH-2, Bear Valley – First surveyed in 2012. The cross section and long profile show up to 9 inches of erosion since 2015 over a length of about 60 feet (Figure 60 and Figure 61). This is associated with an outside bend and is not representative of wider reach conditions. The channel is stable (grass swale) upstream for 100 feet or more to the nearest culvert, and depositional (with the channel almost completely filled with sediment) for more than 100 feet downstream. The volume of sediment depositing downstream appears greater than the volume lost upstream, implying that some of the sediment is reaching the channel from outside the monitored reach. This is supported by the evidence of fine sediment depositing in and downstream of the upstream culvert (upstream of the monitored site). The area around the monitored site is currently being developed with mass grading nearby. Bear Valley has experienced a relatively large number of flow events during the monitoring period, including an event of 20 cfs (compared with an estimated Q2 of 13 cfs per USGS 2012 and 5 cfs per USGS 1977). It is possible that these events have caused local scour at the test site while a combination of natural and anthropogenic sediment washed in from the watershed areas has caused more widespread deposition around the cross section. The bed composition remains unchanged as labile. The original secondary indicators showing probability of incision appear to have been misclassified in 2009, resulting in a vertical susceptibility of High rather than Very High (as the current classification shows). This does not, however, affect the overall channel rating since the High and Very High classes are aggregated into a single class (High). The lateral susceptibility classification was confirmed as Medium (unchanged from the 2009 classification).

DH-3, MDS – First surveyed in 2013, the cross section and long profile show signs of erosion upstream of, and through, the cross section, and deposition downstream to the nearest culvert (Figure 62 and Figure 63). The cross section is almost at the “hinge point” between erosion and deposition and thus appears relatively stable, but there is evidence from field and long profile of up to 1 foot of erosion and deposition. In addition, there is active bank slumping upstream of the monitored cross section, indicating more active erosion than some of the bed scour observed in other sites. The downstream deposition appears to be influenced by a culvert, which may be creating a backwater condition; without the backwater and grade control, it is possible that this site would be eroding throughout.

The vertical and lateral susceptibility conditions were confirmed and unchanged from the 2009 assessment. The main development for which this site was selected to assess has not taken place yet, but this watershed has been experiencing ongoing development and grading since 2005 (not covered by the HMP flow control requirement) and it is

possible that erosion is a result of that earlier disturbance. Of all the sites re-assessed this is the only one where the erosion appears to involve more than

mobilization of previously deposited bed sediment, with some active bank slumping and widening.

RM-1, Deer Valley – First surveyed in 2011. The cross section shows a few inches of possible aggradation in the base of the channel cross section between 2013 and 2015, and a general filling in of irregularities is shown in the long profile (Figure 64 and Figure 65). This was confirmed by the field assessment, which found a few inches of sand (74% sand, d50 of 2mm) covering what had previously been classified as a gravel bed (d50 of 25mm). Although not activated in previous years, Deer Valley did experience flow and bed sediment transport in January 2016, with a peak flow of 1.2 cfs (relative to an estimated Q2 of 5 cfs per USGS 2012 and 2 cfs per USGS 1977). It appears that small quantities of bedload and suspended load from the January 7th event were deposited in the bed, overlaying the armored gravel bed encountered in previous years. This change in bed type causes a reclassification of the channel vertical susceptibility from Low to Very High. The original lateral susceptibility factors were confirmed and unchanged, but because the vertical susceptibility increased from Low to Very High, the lateral classification increased



from Medium to High. The overall susceptibility of the channel changed from Medium to High as a result of the change in bed materials.

This reevaluation using the stream classification tools in TR 606 highlights the need to base the bed material classification on a sufficiently representative length of channel; in this case the entire 200 feet surveyed plus several hundred feet of channel visually inspected downstream of the site appears to have been covered in a layer of sand several inches thick, resulting in reclassification as a labile bed. In reality, this channel probably functions as a gravel bed channel with Medium or Low susceptibility; during relatively dry years such as the monitoring period fine sediment likely washes in from the watershed slopes and partially fills the channel, but during wetter years or in response to urbanization, we might expect the fine sediment to wash out, revealing the more resistant gravel bed beneath.

In future updates to the HMP, it may be worth considering adding guidance to the channel assessment to excavate several inches of bed before making the bed classification, so that thin sand veneers of this type do not bias the classification.

RM-2, Sycamore Canyon – First surveyed in 2012, the cross section shows up to 6 inches and the long profile up to a foot of aggradation, mostly between 2015 and 2016 (Figures 66 and 67). This was confirmed by observations of sand deposits in the lower 250 feet of the reach. The sand layer changed the vertical susceptibility with the channel moving from gravel bed in 2009 (d50 of 45 mm, 12% sand) to labile (d50 of 2 mm, 74% sand). As with the other reference sites, Sycamore seems to have aggraded in the 2015–2016 wet season as a wetter-than-average winter washed fine sediment in from the watershed but did not trigger channel erosion. Interestingly, no flow was measured at Sycamore throughout the monitoring period, suggesting that a relatively large volume of fine sediment was washed in from the surrounding hillslopes and stream banks rather than transported down the channel (though it is possible that this site was active during the summer 2015 event, which occurred when the flow sensors were not operating).

The influx of fine sediment has resulted in a change in vertical susceptibility from Medium in 2009 to Very High in 2016. As with Deer Valley, the true vulnerability is probably represented by the original Medium rating, since a few inches of erosion in the sand bed would expose the more resistant gravel bed. The lateral stability criteria were confirmed and unchanged, but because the vertical susceptibility had increased the lateral susceptibility also increased from Medium to High.

RH-1, Ramona – First surveyed in 2011. This site had no detectable change in the cross section and small amounts of apparent change in the long profile, with 2-4 inches of deposition in some areas (Figure 68 and Figure 69). The bed material (sand) was unchanged. No flow has been observed or monitored at this site during the course of the monitoring project, though surface wash into the creek from the banks and surrounding slopes may have occurred, and is supported by the visual appearance of the creek bed. There was a large event in this area in the summer of 2015 when the flow sensors were not deployed. All vertical and lateral channel stability indicators from the original assessment were confirmed as unchanged. Note that this site is incised (Channel Evolution Model [CEM] Stage II) but the presence of mature oak trees in the base of the channel suggests that it has been vertically stable for at least an estimated date of 50 years. Older oak trees at the top of bank with exposed roots suggest a bookend date that precedes erosion (estimated age of around 100 years). This site appears to have incised historically but been stable for a long time under the present regime of very low runoff from the undeveloped (but grazed) watershed.



RH-2, Schoolhouse Canyon – First surveyed in 2012, this site has not changed significantly. The cross section shows about 6 inches of aggradation since 2012, and the long profile shows from 0 to 2 feet of aggradation over 100 feet of long profile, tapering to no detectable change just upstream of the cross section (Figure 69 and Figure 70). Field observations support the cross section, with extensive evidence of sand deposition in the bed for several hundred feet downstream of the cross section. No flows were recorded at the site from the start of monitoring in 2012 until the event of January 7, 2016, where a peak flow of around 6 cfs was measured (with an estimated Q2 of 26 cfs per USGS 2012 and 12 cfs per USGS 1977).

Bed and suspended sediment transport were measured during this event. There was also a large event in this area in the summer of 2015 when the flow sensors were not deployed. This site was burned in the 2007 Witch Fire, and it appears that fine sediment from the watershed may be reaching the channel from steeper reaches and side slopes upstream and depositing in the gentler reach where monitoring is taking place. The bed material recorded in the revised assessment had a sand content that increased from 54% in 2009 to 100% in 2016, though since the channel was originally classified as labile this did not affect the vertical susceptibility rating. The channel was originally classified as CEM stage III or IV (incised and/or widening). As with many San Diego channels, this one shows evidence of cycles of erosion and incision followed by deposition, and re-incision, making long-term classification challenging. The channel has been CEM stage III in the past, but would probably be considered either a filled stage I or CEM stage V (widened and created new floodplain). Neither condition is covered in the TR 606 channel susceptibility calculator. Assuming that CEM stage V is equivalent to CEM stage I, the original classification from 2009 is confirmed (there is no effect on vertical susceptibility, whichever option is selected). In future updates of the HMP it may be worth providing guidance on how to interpret channels such as this one. The lateral susceptibility condition was confirmed and unchanged.

UM-1, Flanders Canyon – First surveyed in 2011. The cross section shows up to 1 foot of incision since 2009 (mostly since 2015) while the long profile shows that incision to cover a length of around 300 feet of channel, with about 100 feet of aggradation downstream (Figure 71 and Figure 72). Field observations show that the area of deposition extends further downstream beyond the survey limits, and appears to approximately match the volume eroded upstream. Review of the long profile appears to show a pulse of finer sediment migrating through the monitored reach over the last 5 years, with a pulse in 2011–2012 and a second pulse in 2015–2016. The overall bed change is about 1 foot through the reach. The particle count shows that the bed in the cross section vicinity has coarsened (d50 of 32 mm in 2016 compared with 19 mm in 2009) as fine sediment has been washed downstream. The other vertical susceptibility criteria were confirmed and unchanged, and the rating is unchanged at Medium. The lateral susceptibility criteria were confirmed. Overall, this site appears to be experiencing a pulse of sediment transport but not undergoing systematic change of the bankfull channel.

UH-2, Saratoga – First surveyed in 2011. The surveys show slight evidence of change at the cross section and more evidence of upstream erosion and downstream deposition in the long profile (Figure 73 and Figure 74). This was confirmed in the field; there is an active head cut and a scour pool upstream of the cross section, and about an inch of sand appears to have been deposited over the bed downstream. The vertical and lateral susceptibility criteria were checked and confirmed per the 2009 assessment. The primary dynamic at this site is active erosion of a 5-foot-high headcut, which has migrated about 9 feet in 5 years. This headcut is likely an indicator of incision that occurred earlier in the watershed’s development and that is still migrating through the system.



ii. Channel Slope Comparisons In general, the receiving channels have maintained similar channel slopes between monitoring periods (Table 16). The sites with the highest variability were Schoolhouse Canyon (SD=0.010) and Bear Valley (SD=0.006), while the remaining sites had lower standard deviations between 0.001 and 0.003. Some channel profiles increased in slope over time, while others decreased, but most of these changes were slight (Appendix D). Much of the variation in slope can be attributed to the selection and spacing of survey points along the thalweg (channel invert).

TABLE 16 COMPARISON OF AVERAGE LONGITUDINAL PROFILE SLOPES

Site Name

Channel Slope by Survey Year Average

Slope Standard Deviation 2011 2012 2013 2014 2015 2016

Otay Village - 0.030 0.031 0.034 - 0.029 0.031 0.002

Bear Valley - 0.016 0.007 0.01 0.005 0.018 0.011 0.006

MDS - - 0.031 0.034 0.035 0.029 0.032 0.003

Deer Valley 0.024 0.026 0.026 - 0.0253 0.0247 0.025 0.001

Sycamore Canyon

- 0.016 0.012 - 0.0126 0.0128 0.013 0.002

Ramona Grasslands

0.023 0.023 0.025 - 0.0248 0.023 0.024 0.001

Schoolhouse Canyon

- 0.051 0.071 - 0.0596 0.0503 0.058 0.010

Flanders Canyon

0.012 0.012 0.01 0.01 0.0105 0.0124 0.011 0.001

Saratoga 0.007 0.009 0.008 0.007 0.0053 0.006 0.007 0.001

iii. Summary of Channel Changes This section summarizes the channel changes inferred from the cross section and profile data, and compared with measured LOD. In addition, we verify those inferences with geomorphic observations as many of the sites had undergone change that was unresolvable by the surveys.

In general, little physical change has been observed and verified at the receiving channel monitoring sites. Plots of channel cross sections and profiles show up to 3.5 feet of change in some locations (Saratoga), but much of the inferred change can be attributed to inter-annual survey error, which averaged 1.1 feet. This value is large when compared with those from the LOD analysis based on 2015 cross section replicates (Table 17). Out of all of the monitoring sites, Saratoga has experienced the most verifiable change. Small headcuts were observed and the channel profile has gradually declined, which is an indicator of incision. Further, pools upstream of the monitoring location have deepened over time indicating bed scour (Figure 50).



TABLE 17 SUMMARY OF CHANNEL CHANGES INFERRED FROM SURVEY*

Monitoring Site

Largest Change Inferred from Survey Plots (feet)

Change Verified with Field Observations? Potential Inter-

annual Survey Error (ft) Cross Section Long Profile Cross Section Long Profile

Otay Village 1.06 0.98 no no 1.06

Bear Valley 0.68 0.43 no yes 0.68

MDS 1.03 0.62 no maybe 1.03

Deer Valley 0.53 0.71 yes no 0.71

Sycamore Canyon

0.5 0.2 no no 0.5

Ramona Grasslands

0.2 0.64 no no 0.64

Schoolhouse Canyon

0.78 1.7 no no 1.7

Flanders Canyon 2.35 0.82 no maybe 2.35

Saratoga 2.28 3.5 yes yes -

TABLE 18 LIMITS OF DETECTION (LOD) ANALYSIS FROM THE 2015 RECEIVING CHANNEL SURVEYS

Monitoring Site

Sediment Variation (z) Survey Variation (s) Limit of Detection*

d84 (mm)

d50 (mm)

d84-d50 (ft)

average (ft)

maximum (ft)

average (ft)

maximum (ft)

Sycamore Canyon 85 47 0.01 0.00 0.03 0.0 0.1

Schoolhouse Canyon 110 3.8 0.03 0.009 0.26 0.1 0.6

Deer Valley 47 23 0.01 0.02 0.1 0.1 0.2

Flanders Canyon Sections 1&2

40 18 0.01 0.004 0.02 0.0 0.1

Flanders Canyon Sections 2&3

40 18 0.01 0.07 0.19 0.1 0.4

* LOD was assessed using the average and maximum observed survey measurement error.

VI. Conclusions

A. Effectiveness Assessment The HMP monitoring program was designed so that individual elements (low-flow threshold applicability, BMP performance, and cross section stability) could be assessed both individually and collectively to provide insight into the performance of the HMP. For example, Table 19 shows how different outcomes in the three different elements could be collectively interpreted.



The monitoring has been successful in integrating the low-flow threshold analysis and the channel stability assessment to reach several conclusions:

1. The use of multiple low-flow thresholds for different channel types (as opposed to the single low-flow threshold adopted by many HMPs) is well supported by the observed sediment transport rating curves that show a wide range of sediment transport characteristics across San Diego County. As Table 12 shows, there is an order of magnitude variation in observed low-flow thresholds for initiation of significant sediment transport in the nine channels monitored. Use of three thresholds is more reflective of actual field conditions in San Diego County and avoids unnecessarily conservative flow controls where receiving waters are less susceptible to erosion.

2. The low-flow thresholds assigned by the HMP to the Southern California Coastal Water Research Project channel susceptibility class (e.g., 0.3 Q2 for MEDIUM susceptibility channels) are generally in line with, or slightly conservative with respect to, the observed points at which sediment transport rates markedly increase, as estimated using two different methods (qualitative and statistical). The low-flow thresholds as estimated in the HMP have been developed to be protective of the receiving waters from excess erosion.

3. The low-flow thresholds for the monitored streams would control 95% of the cumulative erosion up to the 10-year flow (i.e., 95% of erosion within the range of geomorphically significant flows).

TABLE 19 INTERPRETATION OF HYPOTHETICAL MONITORING RESULTS

Significant sediment transport below low-flow threshold?

BMP controls intended flow

range?

Receiving channel cross section stable? Interpretation Cross check

No Yes Yes HMP is effective Look upstream / downstream to verify overall

stability

Yes Yes No Channel more sensitive than classified

Consider modifying channel classification method

No Yes No External driver (e.g., historic disturbance, large flood)

Look upstream / downstream for cause of

degradation

No No Yes Channel less sensitive than classified

Consider modifying channel classification method

No No No BMP not working Post mortem BMP & channel rehabilitation

Yes No No BMP and classification failed

Considering modifying channel classification

scheme, post mortem BMP, & channel rehabilitation



VII. References Bledsoe, B.P., Hawley, R.J., Stein, E.D., Booth, D.B., 2010. Hydromodification screening tools:

field manual for assessing channel susceptibility. Technical report 606. Southern California Coastal Water Research Project, Costa Mesa, CA.

Brown and Caldwell, 2011. Final hydromodification management plan. Technical report dated March 11, 2011. Prepared for the County of San Diego, California. Prepared by Brown and Caldwell, San Diego, CA.

Clear Creek Solutions, 2011. San Diego Hydrology Model [Software]. Olympia, WA. Download available from: http://www.clearcreeksolutions.com/ProductDetails.asp?ProductCode=SDHM

ESA (Environmental Science Associates), 2015. BMP monitoring site selection and implementation. Technical memorandum dated June 26, 2015. Prepared for the San Diego Monitoring Subworkgroup and Municipal Stormwater Copermittees. Prepared by ESA, San Francisco, CA.

ESA PWA (Environmental Science Associates – Philip Williams and Associates) and Weston, 2013. San Diego Hydromodification Management Plan – Monitoring plan revision technical report. Report dated December 20, 2013. Prepared for the County of San Diego and San Diego Regional Stormwater Copermittees. Prepared by ESA PWA, San Francisco, CA and Weston Solutions, Carlsbad, CA.

ESA PWA, 2013. San Diego Regional HMP – Monitoring sites selection summary. Technical memorandum dated October 29, 2013. Prepared for the County of San Diego, Watershed Protection Program. Prepared by ESA PWA, San Francisco, CA.

Gotvald, A.J., Barth, N.A., Veilleux, A.G., and Parrett, Charles, 2012, Methods for determining magnitude and frequency of floods in California, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2012–5113, 38 p., 1 pl.

Hawley, R.J., Bledsoe, B.P., 2011. How do flow peaks and durations change in suburbanizing semi-arid watersheds? A southern California case study. Journal of Hydrology 405.

National Center for Atmospheric Research Staff (Eds). Last modified 23 Dec 2015. "The Climate Data Guide: PRISM High-Resolution Spatial Climate Data for the United States: Max/min temp, dewpoint, precipitation." Retrieved from https://climatedataguide.ucar.edu/climate-data/prism-high-resolution-spatial-climate-data-united-states-maxmin-temp-dewpoint.

PWA (Philip Williams and Associates). 2009. Developing geomorphically-based flow control guidelines for the San Diego HMP. Presentation. Prepared for the County of San Diego, San Diego, CA. Prepared by PWA, San Francisco, CA.

USEPA (United States Environmental Protection Agency), 2011. Storm Water Management Model [Software]. Athens, GA. Download available from: http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/#Downloads



USEPA (United States Environmental Protection Agency), 1997. Hydrological Simulation Program-FORTRAN [Software]. Athens, GA. Download available from: http://www.epa.gov/ceampubl/swater/hspf/

Warrick, J. A., 2014. Trend analyses with river sediment rating curves. Hydrologic Processes. DOI: 10.1002/hyp.10198

Weston (Weston Solutions), 2012a. Final quality assurance project plan for effectiveness assessment monitoring for the San Diego Hydromodification Management Plan. Document dated May 23, 2012. Prepared for San Diego County Municipal Copermittees. Prepared by Weston Solutions, Inc., Carlsbad, CA.

Weston, 2012b. No title. Technical memorandum dated May 18, 2012. Prepared for the County of San Diego, Watershed Protection Program, San Diego, CA. Weston Solutions, Inc., Carlsbad, CA.

Weston, 2014. Effectiveness Assessment Monitoring for the San Diego Hydromodification Management Plan: Draft Wet Weather Event Monitoring Report. Technical report dated June 12, 2014. Prepared for the County of San Diego. Prepared by Weston Solutions, Inc., Carlsbad, CA.

Weston, 2015. Effectiveness Assessment Monitoring for the San Diego Hydromodification Management Plan: Draft Wet Weather Event Monitoring Report. Technical report dated June 12, 2015. Prepared for the San Diego County Municipal Copermittees. Prepared by Weston Solutions, Inc., Carlsbad, CA.

Weston, 2016. Effectiveness Assessment Monitoring for the San Diego Hydromodification Management Plan: Draft Wet Weather Event Monitoring Report. Technical report dated May, 2016. Prepared for the San Diego County Municipal Copermittees. Prepared by Weston Solutions, Inc., Carlsbad, CA.

Weston (Weston Solutions) and ESA (Environmental Science Associates), 2015. Detailed monitoring plan for the San Diego Hydromodification Management Plan. Working Draft. Prepared for the San Diego County Municipal Copermittees. Prepared by ESA, San Francisco, CA and Weston Solutions, Carlsbad, CA.



VIII. List of Preparers This report was prepared by the following ESA staff:

• Darren Bertrand – Task Order Manager

• Rocko Brown, PhD – Managing Associate

• James Gregory, PE – Senior Associate

• James Jackson, PE - Associate

• Andy Collison, PhD – Project Director

• David Pohl, Ph.D., P.E. – Project Manager


San Diego HMP – 2016 Data Analysis Update A-1 ESA / Project No. 211485.08 Technical Report July, 2016

Preliminary Subject to Revision

APPENDIX A – ANALYTICAL EXAMPLES

Appendix A– Analytical Examples



I. De-trended Inflection Analysis Example This section provides a worked example and “walk through” of the de-trended inflection analysis. The first step is developing the rating curve, which in this example we will use the Flanders bedload rating curve data (Figure 1). This data was collected for several events from 2/27/2012 to 3/8/2013 (Weston, 2013). After generating the rating curve the next step is fit a trend to the data. For this example, a power function was used with a relatively good overall fit ( 4.0185 ∗

. with 0.8765).

Figure 4. Bedload rating curve and trend for Flanders.

Now we can “de-trend” the actual data by subtracting the trend from each value. So for each data value, , at the data point the operation is:

, , The de-trended data (Figure 2) is just the original value less the value of any trend that runs through the entire data set. As we can see most values are centered around zero and some are even negative. As we can see, the data retains its units because all we did was simple subtraction. To make the data more useful we have to non-dimensionalize it so we can assess the data relative to its mean. We do this by “standardizing” the data by its mean, , and standard deviation, . For each data value, , at the data point the operation is:

, ,

What this does is place the entire data set, which has now been de-trended, into a context relative to the mean and standard deviation. This means that the data can now be assessed similarly to scores where increments from 0 can be used an indicators of departure from the mean (which is

Flandersy = 4.0185x2.989

R² = 0.8765

0

50

100

150

200

250

0 0.5 1 1.5 2 2.5 3 3.5 4

Qb, B

edload

Discharge

(g/s)

Function of USGS Q2 Estimate




now 0). The levels of significance for normally distributed data are +/-1 = 1 standard deviation, +/-2 = 2 standard deviations, and so on. For the tests used in this monitoring report we used a relaxed Z score of +0.5 standard deviations, which has a 70% probability (Figure 3). While subjective, we felt that a 70% probability was a good benchmark for sediment transport data that is often very complex and noisy. Future monitoring studies should continue to evaluate this threshold as more data becomes available.

Figure 5. De-trended bedload rating curve.

Figure 6. Normal distribution showing area under curve (e.g. probability) for values below 0.5.

‐50

0

50

100

150

200

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Detrended Qb, B

edload

Discharge

(g/s)





The final plot below (Figure 7) shows the de-trended and standardized data with the 0.5 threshold. We can see that the first point to break this value occurs at 1.187Q2.

Figure 7. Standardized residuals for the Flanders bedload rating curve data. The black dashed lines represent a half of a standard deviation. Note that the data range in the above plot has been truncated for clarity. This results in one data point not showing.

‐2

‐1.5

‐1

‐0.5

0

0.5

1

1.5

2

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Stan

darized Bedload

Residuals





II. Event-based Work Curves Example As part of the San Diego HMP, ESA has developed an automated tool in MATLAB to translate sediment and flow data we have collected for several creeks in San Diego County into work curves relating sediment transport rates to a series of flow thresholds for a given receiving channel. The two primary inputs to the tool are flow frequency relationships for the channel, used to set the thresholds between which total bedload and suspended load transport is computed, and a time series of flow and sediment data collected for a measured runoff event. A visual representation of the thresholds concept is shown in Figure 8. The following describes the details of the inputs, outputs, and computational process of the tool.

Figure 8. Sediment work curve and flow threshold example.

Input Data

The flow thresholds adopted for the work curve analysis are defined by the 2-year discharge (Q2), the 10-year discharge (Q10), and an optional user defined threshold (Quser) which can be used to analyze thresholds based on drainage area scaling or other metrics. The thresholds ranges, or ‘bins’, based on these inputs are the following:

Below 0.1Q2 0.1 Q2 to 0.3 Q2




0.3 Q2 to 0.5 Q2 0.5 Q2 to Q2 Q2 to Q10 Above Q10

The user defined discharge is inserted into this list of thresholds depending on where it falls within the range of flow values and will divide a single bin into two individual bins. For example, a Quser between Q2 and Q10 will create a bin from Q2 to Quser, and from Quser to Q10. Once flow thresholds are defined, the user can input a time series data for flow (in ft3/s), bedload transport (grams/s), and suspended sediment transport (ppm, mg/L). For this analysis, it was assumed that each bedload or suspended sediment sample was collected at the same time as the closest flow measurement sample time. The tool can be used to analyze a time series for a single event or a series of consecutive events.

Computation Process

Generally, the process for computing bedload and suspended load transport within each flow bin is accomplished by integrating sediment measurements collected during the timeframe for which flow is within the range defined by a given bin. The following stepwise process is carried out for an individual sampling event and location:

1. Flow thresholds are spliced into the flow measurement time series and sediment values are interpolated at the threshold value.

2. Sample data falling within a given threshold bin is extracted from the time series. 3. Bedload and suspended load values are integrated within a given threshold bin assuming

data is linear between sample points. 4. Steps 2 and 3 are repeated for each flow threshold bin.

These steps are shown graphically in the following pages.

Example 1 – Flanders Canyon, March 8, 2013 Discharge Event

Table 1. Computational flow thresholds for Flanders Canyon.

Threshold Discharge (cfs)

0.1Q2 3.7

0.3Q2 11.1

0.5Q2 18.5

Q2 37

Q10 162




Step 1 - Splice flow thresholds into measured data and interpolate between measurement points. ORIGINAL DATA SPLICED DATA

Time (hh:mm)

Q (cfs) Qb (g/s) SSC (ppm)

Time (hh:mm)

Q (cfs) Qb (g/s) SSC (ppm)

Source

1:45 42.10 33.03 66.00 1:45 42.10 33.03 66.00

2:41 13.28 0.22 26.00 1:55 37.00 27.22 58.92 Interpolated

3:46 50.22 25.69 217.00 2:31 18.50 6.16 33.24 Interpolated

4:08 42.11 23.39 98.00 2:41 13.28 0.22 26.00

4:25 123.84 110.19 309.00 2:50 18.50 3.82 52.97 Interpolated

5:52 74.76 194.99 80.00 3:22 37.00 16.57 148.65 Interpolated

6:11 39.57 6.84 51.00 3:46 50.22 25.69 217.00

6:27 31.35 1.89 35.00 4:08 42.11 23.39 98.00

6:45 23.30 0.83 38.00 4:25 123.84 110.19 309.00

7:19 14.79 1.03 26.00 5:52 74.76 194.99 80.00

6:11 39.57 6.84 51.00

6:16 37.00 5.29 45.99 Interpolated

6:27 31.35 1.89 35.00

6:45 23.30 0.83 38.00

7:04 18.50 0.94 31.23 Interpolated

7:19 14.79 1.03 26.00

Figure 9. Illustration of spliced flow data.

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

180.00

1:00 2:00 3:00 4:00 5:00 6:00 7:00

Discharge

(cfs)

Time step (hh:mm)

Original flow data

Spliced flow threshold data

0.1Q2

0.3Q2

0.5Q2

Q2

Q10




For flow threshold Q2 to Q10 (i.e. between 37 and 162 cfs): SPLICED DATA Load computations

Time (hh:mm)

Q (cfs) Qb (g/s)

SSC (ppm)

Time range(hh:mm)

Bedload transported (kg)

Suspended loadtransport (kg)

1:45 42.1 33.0 66.0 1:45 to 1:55 18.1 42.0

1:55 37.0 27.2 58.9 3:22 to 3:46 29.3 312.7

2:31 18.5 6.2 33.2 3:46 to 4:08 32.4 271.8

2:41 13.3 0.2 26.0 3:46 to 4:10 68.1 487.7

2:50 18.5 3.8 53.0 3:46 to 4:11 801.1 2871.3

3:22 37.0 16.6 148.6 3:46 to 4:12 115.0 120.9

3:46 50.2 25.7 217.0 3:46 to 4:13 1.8 15.3

4:08 42.1 23.4 98.0

Total (Q2 to Q10)

1065.8 4121.5

4:25 123.8 110.2 309.0

5:52 74.8 195.0 80.0

Bedload transported (kg)

Suspended load transport (kg)

6:11 39.6 6.8 51.0 Below 0.1Q2 0.0 0.0

6:16 37.0 5.3 46.0 0.1Q2 to 0.3Q2 0.0 0.0

6:27 31.4 1.9 35.0 0.3Q2 to 0.5Q2 3.9 29.9

6:45 23.3 0.8 38.0 0.5Q2 to Q2 60.9 311.5

7:04 18.5 0.9 31.2 Q2 to Q10 1065.8 4121.5

7:19 14.8 1.0 26.0 Above Q10 0.0 0.0

Figure 10. Illustration of sediment load binning for computation flow thresholds.

The equation for the bedload transported between two timesteps (t2 and t1 in seconds) is:

2

2 111000

Where: Qb = measured bedload transport rate (g/s)

The equation for the suspended load transported between two timesteps (t2 and t1 in seconds) is:

∗ ∗

22 1

28.3 110

Where: Q = measured discharge (ft3/s)

SSC = measured suspended load (ppm, mg/L)

Step 2 – Extract time series data falling within bin range.

Step 3 – Compute transported load by integration (equations shown below).

Step 4 – Repeat steps 2-3 for each bin.

San Diego HMP – 2016 Data Analysis Update B-1 ESA / Project No. 211485.08 Technical Report July, 2016


APPENDIX B - RATING CURVES

Appendix B– Rating Curves

San Diego HMP – 2016 Data Analysis Update C-2 ESA / Project No. 211485.08 Technical Report July, 2016


Figure 11. Bedload rating curve for cobble-bed channels. No data was collected for Flanders during the 2015 and 2016 wet seasons.

Figure 12. Bedload rating curve for cobble-bed channels using a log-log plot. No data was collected for Flanders during the 2015 and 2016 wet seasons.

Otay y = 0.1307x1.2159

R² = 0.0475 Flandersy = 6.378x2.8234

R² = 0.8256Deery = 0.0011x‐0.054

R² = 0.0004

0

50

100

150

200

250

0 0.5 1 1.5 2 2.5 3 3.5 4

Qb, B

edload

Discharge (g/s)


Otay (High, Cobble) Flanders (Med, Cobble) Deer Valley (High, Cobble)

Otay y = 0.1307x1.2159

R² = 0.0475

Flandersy = 6.378x2.8234

R² = 0.8256

Deery = 0.0011x‐0.054

R² = 0.0004

0.00001

0.0001

0.001

0.01

0.1

1

10

100

0.001 0.01 0.1 1 10

Qb, B

edload

Discharge (g/s)






Figure 13. Bedload rating curve for sand-bed channels. Insufficient data was collected to generate s sediment rating curve for Schoolhouse.

Figure 14. Bedload rating curve for sand-bed channels using a log-log plot. Insufficient data was collected to generate s sediment rating curve for Schoolhouse.

Saratogay = 221.25x1.4596

R² = 0.5047

Beary = 12.803x1.0749

R² = 0.4689

MDSy = 3.4489x0.6673

R² = 0.2583

0

100

200

300

400

500

600

700

800

900

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Qb, B

edload

Discharge (g/s)


Saratoga (High, Sand) Bear (Med, Sand) MDS (High, Sand) Schoolhouse (High/Sand)


R² = 0.5047

Beary = 12.803x1.0749

R² = 0.4689

MDSy = 3.4489x0.6673

R² = 0.2583

0.001

0.01

0.1

1

10

100

1000

0.00001 0.0001 0.001 0.01 0.1 1 10

Qb, B

edload

Discharge (g/s)


Saratoga (High, Sand) Bear (Med, Sand) MDS (High, Sand) Schoolhouse (High/Sand)




Figure 15. Suspended load rating curve for cobble-bed channels.

Figure 16. Suspended load rating curve for cobble-bed channels using a log-log plot.

Otayy = 1107.1x0.3187

R² = 0.2089 Flandersy = 72.273x0.6109

R² = 0.3456Deer Valley

y = 1399.7x1.0856

R² = 0.5871

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5 4

Suspen

ded

Sedim

ent (ppm)



Otay y = 1107.1x0.3187

R² = 0.2089 Flandersy = 72.273x0.6109

R² = 0.3456

Deer Valleyy = 1399.7x1.0856

R² = 0.5871

1

10

100

1000

0.0001 0.001 0.01 0.1 1 10

Suspended

Sed

imen

t (ppm)






Figure 17. Suspended Load Rating for sand-bed channels. Insufficient data was collected to generate s sediment rating curve for Schoolhouse.

Figure 18. Suspended Load Rating for sand-bed channels using a log-log plot. Insufficient data was collected to generate s sediment rating curve for Schoolhouse.


R² = 0.5818

Bear Valleyy = 403.5x0.295

R² = 0.2195

MDSy = 7624.4x0.2671

R² = 0.2845

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Suspended

Sed

imen

t (ppm)


Saratoga (High, Sand) Bear Valley (Med, Sand)

MDS (High, Sand) Schoolhouse (High/Sand)


R² = 0.5818

Bear Valleyy = 403.5x0.295

R² = 0.2195

MDSy = 7624.4x0.2671

R² = 0.2845

1

10

100

1000

10000

0.00001 0.0001 0.001 0.01 0.1 1 10

Suspended

Sed

imen

t (ppm)


Saratoga (High, Sand) Bear Valley (Med, Sand)

MDS (High, Sand) Schoolhouse (High/Sand)



APPENDIX C - WORK CURVES

Appendix C– Work Curves



FLANDERS WORK CURVES:

Figure 19. Flanders work curve for February 27, 2012.

Figure 20. Flanders work curve for March 17, 2012.

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

14:51 16:03 17:15 18:27 19:39

Bedload

Transport (g/s)

Discharge

(cfs)

Time of Sampling ‐ February 27, 2012 (HH:MM)

Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

9:57 11:09 12:21 13:33 14:45 15:57 17:09 18:21

Bedload

Transport (g/s)

Discharge

(cfs)

Time of Sampling ‐March 17, 2012 (HH:MM)

Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 21. Flanders work curve for April 13, 2012.

Figure 22. Flanders work curve for December 13, 2012.

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

14:33 15:45 16:57 18:09

Bedload

Transport (g/s)

Discharge

(cfs)

Time of Sampling ‐ April 13, 2012 (HH:MM)

Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

8:41 9:53 11:05 12:17 13:29

Bedload

Transport (g/s)

Discharge

(cfs)

Time of Sampling ‐ December 13, 2012 (HH:MM)

Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 23. Flanders work curve for January 25, 2013.

Figure 24. Flanders work curve for February 19, 2013.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

9:33 10:45 11:57 13:09 14:21 15:33 16:45 17:57

Bedload

Transport (g/s)

Discharge

(cfs)

Time of Sampling ‐ January 25, 2013 (HH:MM)

Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

22:49 23:18 23:47 0:15 0:44 1:13

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 25. Flanders work curve for March 8, 2013.

0.00

50.00

100.00

150.00

200.00

250.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

1:45 2:57 4:09 5:21 6:33

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




SARATOGA WORK CURVES:

Figure 26. Saratoga work curve for February 27, 2012.

Figure 27. Saratoga work curve for March 17, 2012.

0

100

200

300

400

500

600

0

5

10

15

20

25

30

35

40

15:47 16:59 18:11 19:23 20:35 21:47 22:59

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

100

200

300

400

500

600

700

800

900

0

5

10

15

20

25

30

35

40

45

50

8:42 11:06 13:30 15:54 18:18

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)





Figure 29. Saratoga work curve for December 13, 2012.

0

50

100

150

200

250

300

350

0

5

10

15

20

25

30

35

40

45

50

17:17 18:29 19:41 20:53

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

20

40

60

80

100

120

140

160

180

0

5

10

15

20

25

30

3:55 6:19 8:43 11:07 13:31

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 30. Saratoga work curve for January 25, 2013.

Figure 31. Saratoga work curve for February 8, 2013.

0

10

20

30

40

50

60

70

80

90

0

5

10

15

20

25

30

7:50 9:02 10:14 11:26 12:38 13:50 15:02 16:14

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

5

10

15

20

25

30

35

0

5

10

15

20

25

30

14:03 15:15 16:27 17:39 18:51 20:03

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)





Figure 33. Saratoga work curve for October 29, 2013.

0

20

40

60

80

100

120

140

160

0

5

10

15

20

25

30

6:50 7:18 7:47 8:16 8:45

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

10

20

30

40

50

60

0

5

10

15

20

25

30

1:04 1:33 2:02 2:31 3:00 3:28

Bedload

Transport (g/s)

Discharge

(cfs)

Time of Sampling ‐ October 29, 2013 (HH:MM)

Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)






0

5

10

15

20

25

30

35

40

45

0

5

10

15

20

25

30

15:01 15:30 15:59 16:27 16:56

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0

5

10

15

20

25

30

12:38 13:07 13:36 14:05 14:34 15:02

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)





0

20

40

60

80

100

120

140

160

0

5

10

15

20

25

30

17:23 18:00 18:33 19:01 19:42 20:36

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q

Q (cfs)

Qb (g/s)




BEAR VALLEY WORK CURVES:

Figure 37. Bear Valley work curve for December 13, 2012.

Figure 38. Bear Valley work curve for March 8, 2013.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

6:27 7:39 8:51 10:03 11:15 12:27 13:39

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

2:37 3:49 5:01 6:13

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 39. Bear Valley work curve for February 28, 2014.


0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

7:26 9:50 12:14 14:38 17:02

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

0.5

1

1.5

2

2.5

3

3.5

4

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

18:00 19:12 20:24 21:36 22:48 0:00

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)






0

2

4

6

8

10

12

14

16

18

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

8:24 9:36 10:48 12:00 13:12 14:24

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

2

4

6

8

10

12

14

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

5:45 6:14 6:43 7:12 7:40 8:09 8:38

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 43. Bear Valley work curve for March 1, 2015.

Figure 44. Bear Valley work curve for January 6, 2016.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

8:38 9:07 9:36 10:04 10:33 11:02 11:31 12:00

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0

2

4

6

8

10

12

14

14:25 14:39 16:00 16:22 16:47 17:53 18:32

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q

Q (cfs)

Qb (g/s)




Figure 45. Bear Valley work curve for March 11, 2016

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0

2

4

6

8

10

12

14

16:38 17:01 17:18 17:36 18:01 18:27 18:49 19:09

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q

Q (cfs)

Qb (g/s)




MDS WORK CURVES:

Figure 46. MDS work curves for February 28, 2014.

Figure 47. MDS work curves for December 17, 2014.

0.000

0.050

0.100

0.150

0.200

0.250

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

17:05 17:19 17:33 17:48 18:02 18:17 18:31

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

6:14 6:28 6:43 6:57 7:12 7:26 7:40 7:55 8:09

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




Figure 48. MDS work curves for March 2, 2015.

Figure 49. MDS work curves for March 7, 2016.

0

1

2

3

4

5

6

0

2

4

6

8

10

12

14

13:26 13:33 13:40 13:48 13:55 14:02 14:09

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb g/s)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0

2

4

6

8

10

12

14

9:29 10:01 10:27

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




OTAY VILLAGE WORK CURVES:

Little or no bedload was recorded for the March 8, 2013 and March 1, 2014 storm events.

Figure 50. Otay Village work curves for December 12, 2014.

Figure 51. Otay Village work curves for December 17, 2014.

0

0.005

0.01

0.015

0.02

0.025

0

2

4

6

8

10

12

14

16

18

20

12:14 12:28 12:43 12:57 13:12 13:26 13:40

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

0

2

4

6

8

10

12

14

16

18

20

5:45 6:14 6:43 7:12 7:40 8:09

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




SCHOOLHOUSE WORK CURVES:

Figure 52. Schoolhouse work curves for March 11, 2016.

0

20

40

60

80

100

120

140

160

0

5

10

15

20

25

30

17:23 18:00 18:33 19:01 19:42 20:36

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)




DEER VALLEY WORK CURVES:

Figure 53 Deer Valley work curves for January 7, 2016.

CUMULATIVE BEDLOAD TRANSPORT:

Figure 54. Best-fit cumulative work curves for bedload transport using a 95% threshold.

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0

1

2

3

4

5

6

11:05 11:53 12:35 13:23 15:08

Bedload

Transport (g/s)

Discharge

(cfs)


Q2

0.5Q2

0.3Q2

0.1Q2

Q (cfs)

Qb (g/s)

Flandersy = ‐0.1378x + 1.0187

R² = 0.8978

Saratogay = 0.822x2 ‐ 1.2534x + 1.0544

R² = 0.9028

Bear y = 0.5421x2 ‐ 0.7142x + 0.925

R² = 0.2511

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Percent Bedload

Above Q/Q

2

Q/Q2 (USGS 2012)

Flanders Saratoga Bear Valley Threshold

San Diego HMP – 2016 Data Analysis Update D-1 ESA / Project No. 211485.08 Technical Report July, 2016


APPENDIX D - CHANNEL SURVEYS

Appendix D – Channel Surveys



Figure 58. Otay Village cross section. No channel changes were observed during field surveys.

Figure 59. Otay Village longitudinal profile. Average channel slope has not changed significantly. Observed variations are likely due to survey station selection. Cross section is located at Station 1+39 (arrow).

490

492

494

496

498

500

502

0 10 20 30 40 50 60 70 80

Elevation (ft‐NAVD)

Station (ft)

2012

2013

2014

2016

2016 slopey = 0.0285x + 488.507

R² = 0.9613

486

488

490

492

494

496

498

0 50 100 150 200 250


Station (ft)

2012

2013

2014

2016




Figure 60. Bear Valley cross section. Minor bed scour was observed. Differences along the right floodplain are due to differences in survey point selection.

Figure 61. Bear Valley longitudinal profile. The channel has incised and widened upstream, but the channel remains stable/depositional near the monitoring site. Cross section is located at Station 2+04 (arrow).

661

661.5

662

662.5

663

663.5

664

664.5

665

20 30 40 50 60 70 80 90 100 110


Station (ft)

2012

2013

2014

2015

2016

2016 profiley = 0.018x + 658.545

R² = 0.9562

658

659

660

661

662

663

664

665

666

667

668

100 150 200 250 300 350


Station (ft)

2012

2013

2014

2015

2016




Figure 62. MDS channel cross section. No channel changes were observed. Observed variations are attributed to cross-section survey angle and station selection.

Figure 63. MDS longitudinal profile. Cross section is located at Station 2+25 (arrow). Some deposition may have occurred upstream of the cross-section. A small headcut was observed downstream of the cross-section in 2014.

1624

1626

1628

1630

1632

1634

1636

10 20 30 40 50 60 70 80

Elevation (NAVD88)

Station (ft)

2013

2014

2015

2016

2016 profiley = 0.029x + 1620.3

R² = 0.9451

1622

1624

1626

1628

1630

1632

1634

100 150 200 250 300 350

Elevation (NAVD88)

Station (ft)

2013

2014

2015

2016




Figure 64. Deer Valley cross section. Channel remains relatively unchanged. The toe of the right bank was trampled by deer (arrow). Not surveyed in 2014.

Figure 65. Deer Valley longitudinal profile. The channel gradient has not changed. Observed variations are due to survey station selection. Cross section is located at Station 0+94 (arrow). Not surveyed in 2014.

219

220

221

222

223

224

225

‐5 0 5 10 15 20 25 30 35 40


Station (ft)

2011

2012

2013

2015

2016

2016 profiley = 0.0247x + 217.462

R² = 0.9888

216

217

218

219

220

221

222

223

224

‐20 0 20 40 60 80 100 120 140 160 180 200


Station (ft)

2011

2012

2013

2015

2016




Figure 66. Sycamore Canyon cross-section. Variations in topography along the banks can be attributed to surveyor station selection. Not surveyed in 2014.

Figure 67. Sycamore Canyon channel profile. No change in profile observed. Channel cross section located at Station 2+70 (arrow). Not surveyed in 2014.

814.5

815

815.5

816

816.5

817

817.5

818

818.5

819

‐5 5 15 25 35 45 55


Station (ft)

2012

2013

2015

2016

2016 profiley = 0.0128x + 812.309

R² = 0.9541

812

813

814

815

816

817

818

100 150 200 250 300 350 400


Station (ft)

2012

2013

2015

2016




Figure 68. Ramona Grasslands cross section. No change observed in cross section. Not surveyed in 2014.

Figure 69. Ramona Grasslands longitudinal profile. No change observed. Cross section located at Station 2+15 (arrow). Not surveyed in 2014.

1340

1342

1344

1346

1348

1350

1352

20 30 40 50 60 70 80


Station (ft)

2011

2012

2013

2015

2016

2016 profiley = 0.023x + 1335.632

R² = 0.9774

1335

1336

1337

1338

1339

1340

1341

1342

1343

1344

1345

1346

0 50 100 150 200 250 300 350 400


Station (ft)

2011

2012

2013

2015

2016




Figure 70. Schoolhouse Canyon cross section. Changes in low flow channel and overbank areas are attributed to surveyor point selection. Not surveyed in 2014.

Figure 71. Schoolhouse Canyon longitudinal profile. Little change observed along surveyed profile. Variations between 2012 and 2013 are due to larger station spacing of the original survey. Cross section is located at Station 2+48 (arrow). Not surveyed in 2014.

507

508

509

510

511

512

513

514

515

30 40 50 60 70 80 90 100 110 120


Station (ft)

2012

2013

2015

2016

2016 profiley = 0.0503x + 497.33

R² = 0.9874

500

502

504

506

508

510

512

514

516

140 190 240 290 340


Station (ft)

2012

2013

2015

2016




Figure 72. Flanders Canyon cross section. Small variations in bed elevation may be due to survey variability or minor erosion and sedimentation.

Figure 73. Flanders Canyon longitudinal profile. Some incision may have occurred between Station 1+50 and 2+70 since the original survey in 2011, but this may also be attributed to surveying the channel center line versus the thalweg (lower elevation). Overall, the channel slope has remained stable. The channel cross section is located at Station 2+10 (arrow).

225

226

227

228

229

230

231

232

233

234

235

100 120 140 160 180 200 220 240 260 280


Station (ft)

2011

2012

2013

2014

2015

2016

2016 profiley = 0.0124x + 223.47

R² = 0.8794

223

224

225

226

227

228

229

50 100 150 200 250 300 350


Station (ft)

2011

2012

2013

2014

2015

2016




Figure 74. Saratoga cross section. Minor erosion and sedimentation has been observed in the channel thalweg since the 2011 survey. The right overbank area has not been resurveyed from 2012 to 2016, since no change in the bank was observed and poison oak covers much of the floodplain.

Figure 75. Saratoga longitudinal profile. The channel has incised slightly since the 2011 survey, and headcuts have migrated upstream and deepened pools near Station 2+00 and 2+50. The channel cross-section in located at Station 1+40 (arrow).

422

424

426

428

430

432

434

436

20 30 40 50 60 70 80 90


Station (ft)

2011

2012

2013

2014

2015

2016

2016 profiley = 0.006x + 423.88

R² = 0.2044

421

422

423

424

425

426

427

428

429

0 50 100 150 200 250 300


Station (ft)

201120122013201420152016




MDS ORIGINAL – MDS 2016 – MDS

Downstream Downstream

Upstream Upstream Figure 76. MDS Site Initial and 2016 Survey Downstream and Upstream Comparison Photos.




ORIGINAL – MDS 2016 – MDS

Left Bank

Left Bank

Right Bank Right Bank Figure 77. MDS Site Initial and 2016 Survey Left Bank and Right Bank Comparison Photos.




BEAR VALLEY ORIGINAL – BEAR VALLEY 2016 – BEAR VALLEY


Upstream Upstream Figure 78. Bear Valley Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – BEAR VALLEY 2016 – BEAR VALLEY

Left Bank

Left Bank

Right Bank Right Bank Figure 79. Bear Valley Site Initial and 2016 Survey - Left Bank and Right Bank Comparison Photos.




DEER VALLEY ORIGINAL – DEER VALLEY 2016 – DEER VALLEY


Upstream Upstream Figure 80. Deer Valley Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – DEER VALLEY 2016 – DEER VALLEY

N/A Left Bank

Left Bank

Right Bank Right Bank Figure 81. Deer Valley Site Initial and 2016 Survey - Left Bank and Right Bank Comparison Photos.




FLANDERS ORIGINAL – FLANDERS 2016 – FLANDERS


Upstream Upstream Figure 82. Flanders Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – FLANDERS 2016 – FLANDERS

Left Bank

Left Bank

Right Bank Right Bank Figure 83. Flanders Site Initial and 2016 Survey Left Bank and Right Bank Comparison Photos.




RAMONA ORIGINAL – RAMONA 2016 – RAMONA


Upstream Upstream Figure 84. Ramona Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – RAMONA 2016 – RAMONA

Left Bank

Left Bank

Right Bank Right Bank Figure 85. Ramona Site Initial and 2016 Survey Left Bank and Right Bank Comparison Photos.




SARATOGA ORIGINAL – SARATOGA 2016 – SARATOGA


Upstream Upstream Figure 86. Saratoga Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – SARATOGA 2016 – SARATOGA

Left Bank

Left Bank

Right Bank

Right Bank Figure 87. Saratoga Site Initial and 2016 Survey Left Bank and Right Bank Comparison Photos.




SCHOOLHOUSE ORIGINAL – SCHOOLHOUSE 2016 – SCHOOLHOUSE


Upstream Upstream Figure 88. Schoolhouse Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – SCHOOLHOUSE 2016 – SCHOOLHOUSE

Left Bank

Left Bank

Right Bank Right Bank Figure 89. Schoolhouse Site Initial and 2016 Survey Left Bank and Right Bank Comparison Photos.




SYCAMORE ORIGINAL – SYCAMORE 2016 – SYCAMORE


Upstream Upstream Figure 90. Sycamore Site Initial and 2016 Survey - Downstream and Upstream Comparison Photos.




ORIGINAL – SYCAMORE 2016 – SYCAMORE

Left Bank

Left Bank

Right Bank Right Bank Figure91. Sycamore Site Initial and 2016 Survey Left Bank and Right Bank Comparison Photos.

2016 data analysis update - project clean water

Documents