eric strecker4

Application of Ecological Engineering Principals to Water Quality Management

Hydromodification MitigationEric Strecker

1

Hydromodification ManagementHydromodification Management

Eric StreckerEric StreckerEric StreckerEric StreckerGeosyntec ConsultantsGeosyntec Consultants

Gary PalhegyiGary PalhegyiIndependent ConsultantIndependent Consultant

August 2008August 2008

AgendaAgenda

Overview of the Science

Management Strategies– Linking flow controls with channel processes– Integrating multiple stormwater control criteria– Roll of LID in hydromodification management

Project Examples– Contra Costa– LID Design for Hydromodification

HydromodificationHydromodificationModification of the Natural Hydrologic CycleModification of the Natural Hydrologic Cycle

Thompson Creek Flow Rates - Pre & Post Development(modeled for a 716 acre development using HEC-HMS)

140

160 Post-Urban @ 44% connectedimpervious coverPre-Urban, Infiltration = 0.16 in/hr

0

20

40

60

80

100

120

Time (hours)

Dis

char

ge (c

fs)

Critical Flow for Sediment Transport

2-Year Flood Flow - Pre-Urban

Increases Runoff Magnitude, Volume and Duration of Smaller Flows more then Larger Flows

Flow Duration Histogram

1500

2000

2500

3000

3500

eque

ncy

(cou

nt)

Post Condition

Existing Condition

20%

Flow Duration Histogram

quen

cy (c

ount

)

0

500

1000

70656055504540353025201510

Discharge (cfs)

Fre

Hollis (1975)

1 10 100

16%

Discharge (cfs)

Frequency (years)

Freq

Perc

ent C

hang

e

Physical Consequences of Physical Consequences of HydromodificationHydromodification

Intensified sediment transport and erosion processesObserved as excessive erosion, incision and widening

Thompson CreekThompson CreekSanta Clara ValleySanta Clara Valley

Ecological Consequences of Ecological Consequences of HydromodificationHydromodificationPredicted Increase in Average Monthly Stream Flow Volumes

200%

250%

ting

Con

ditio

ns

At Eagles Nest Road, LCC4

0%

50%

100%

150%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Perc

ent C

hang

e fro

m E

xist



2

Key ConceptsKey ConceptsFlow magnitude, volume, frequency of occurrence, duration and timing– are major driving forces that control the physical and ecological

processes in a riparian corridor

Sediment supply is also a key factor that is often not considered Channel stability – requires a balance among flow energy, sediment supply and

channel resilience

Analytical methods– must link watershed hydrology and land development with these

channel processes

Management strategies– must include the full range of geomorphically significant flows

Time integrated metrics (e.g., Erosion Potential)– provide the closest reproduction of these processes

Key Steps in the Key Steps in the Erosion Potential MethodologyErosion Potential Methodology

Characterize the Physical Setting

Perform Geomorphic Assessment

Conduct Continuous Hydrologic ModelingConduct Continuous Hydrologic ModelingConduct Hydraulic/Work & Sediment Transport ModelingEvaluate Sediment Supply ChangesEvaluate Potential Instability, Compliance and/or Design Parameters

Conceptual ModelConceptual Model

Hydrologic modelHydrologic model

Model ScenariosModel Scenarios1)1) PrePre--developeddeveloped2)2) Existing conditionsExisting conditions3)3) PostPost--developeddeveloped

Sediment transport / work modelSediment transport / work model(incl. hydraulics)(incl. hydraulics)

Erosion PotentialErosion PotentialQQss

QQff

Catchment boundary

preQspostQs

Ep∑∑

=

Hydrologic ModelingHydrologic Modeling

Land Use Scenarios– Pre, existing, and future

Climate– Long term continuous hourly records– Full probability distribution

Precipitation-Runoff– Soil moisture accounting– Where applicable snow melt

Calibrated & Verified

Hydraulic & Shear Stress ModelHydraulic & Shear Stress Model(Incorporates geometry, slope, & vegetation)

SKQ ⋅⋅= 49.1

∑ ⋅=

nRAK

3/2

96

Vegetation Vegetation densitydensity

SgRavgavg ρτ =

32

⎟⎟⎠

⎞⎜⎜⎝

⎛=

avg

bavgb n

nττ

87

88

89

90

91

92

93

94

95

0.0 10.0 20.0 30.0 40.0 50.0

P2

R2R1

P3

P4

A1 A2

n2

n3

n4

Boundary Material PropertiesBoundary Material Properties(determine critical shear stress for weakest boundary)

Jet Testing to field measureCritical Shear Stress (τc)

87

88

89

90

91

92

93

94

95

96

0.0 10.0 20.0 30.0 40.0 50.0

ττc bankc bank

ττc bedc bed



3

Effective Work & Sediment Effective Work & Sediment Transport ModelsTransport Models

( )ba cb

n

ττ −⋅= ∑1

( )cb

n

V ττ −⋅= ∑1

MacRae, C.R.

Andrew Simons, Ph.D., National Sedimentation Laboratory

Derek Booth, Ph.D., WSU

Cohesive

MaterialWorkWork

( ) 978.1

1cb

n

VVa −⋅= ∑

Wilcock-Crowe (2003)

b

c

bn

a ⎟⎠⎞⎜

⎝⎛⋅= ∑ ττ

1

TransportTransport

Brownlie (1981)Sand

Sand &Gravelmixtures

Gravel Parker (1990)( )[ ]∑ ⋅⋅⋅=n

DiDgGa

1 50φω

WorkWorkLaguna Creek, Laguna Creek, SacramentoSacramento Oso Canyon, Oso Canyon, TehachapiTehachapi

TransportTransport

Laurel Creek, Laurel Creek, FairfieldFairfield--SuisunSuisun Long Canyon, Long Canyon, Santa ClaritaSanta Clarita

InIn--StreamStreamManagement ObjectivesManagement Objectives

Maintain Baseline Conditions (MacRae, SCVURPPP)– Ep = 1 ± 20%

postWEp

∑=

Maintain Capacity / Supply Ratio (USACE, Soar & Thorne)– CSR = 1 ± 10%

preWEp

∑

supply

capacity

∑∑

=Qs

QsCSR

11

1010

22

55

EE 11

1010

22

55

EE 11

1010

22

55

EE

BaselineBaselinePost with Post with

increased flowsincreased flowsPost w/ 80% reduction in Post w/ 80% reduction in

sediment supplysediment supply

11

0.10.1

0.20.2

0.50.5

EpEp 11

0.10.1

0.20.2

0.50.5

EpEp 11

0.10.1

0.20.2

0.50.5

EpEp

Target EpTarget Ep Post EpPost Ep

AgendaAgenda


Management Strategies– Linking flow controls with channel processesLinking flow controls with channel processes

(ultimate objective)

– Integrating multiple stormwater control criteria

– Roll of LID in hydromodification management

Range of Management Strategies Range of Management Strategies being Used or Proposedbeing Used or Proposed

Stream classificationSite design, LIDPeak flow, velocityyTime of concentrationRunoff volume, groundwater rechargeFlow duration control Instream stabilizationWork & Erosion Potential (Ep)



4

What is Flow Duration Control and What is Flow Duration Control and Why is it Important?Why is it Important?

60

70

80

90

100

(hou

rs)

20

25

30Frequency of Flows

Effective Work Curve

Sediment Transport

Effective Discharge (lbs)

( )bττ

Work Curve (Leopold, 1964)

0

10

20

30

40

50

0 20 40 60 80 100 120 140 160 180 200 220 240

Flows Bin's (cfs)

Freq

uenc

y

0

5

10

15

Qs (lbs/sec)

Qc

( )bcb ττ −

Flow Duration Control Flow Duration Control Is a Design ConceptIs a Design Concept

Stream Discharge

Matched FDC Inflow

Infiltration(LID, diversion, by-pass, recycle)

Qcp

Volume Retained(50% to 90%)

AgendaAgenda






FDC Integrates with Flood ControlFDC Integrates with Flood ControlCommercial developmentArea = 12.2 acres65% impervious surfacesInfiltration rate = 0.5 in/hrMAP = 20 inchesTc = 10 to 20 min

Example Flood Frequency ResultsExample Flood Frequency ResultsCommercial Development ExampleRecord: 1948 to 1990, 12.2 Acres, A/B Soils

8

10

12

e (c

fs)

Predeveloped

Postdeveloped

FDC Mitigated flow

Qcp

65% Impervious surfacesInfiltration = 0.5 in/hr

Flood Frequency Curves (Partial Duration Series)Showing Flood Control Results

10

12

14

16

18

20

rge

(cfs

)

Existing conditions - undeveloped

Proposed project @ 65% IMP

Discharge from FDC BasinPre-Project

Post-Project

Peak flow - design storm

0

2

4

6

1 10 100 1000 10000 100000

Cumulative Duration (hours)

Dis

char

ge

475 14th Street, Suite 400Oakland, CA 94612

FDC Depth = 2 feetFDC Area = 6.1% (0.74 ac)FDC Volume = 1.35 ac-ft

0

2

4

6

8

10

1 10 100Recurrance Interval (years)

Dis

char


Peak Discharge from FDC Basin

100100--Year Storm Tested in FDC BasinYear Storm Tested in FDC Basin100-Year Design Storm Hydrographs showing FDC Basin Performance

15

20

25

ge (c

fs)

Post Project

Pre Project

FDC Basin Outflow

Pre-Project 100-Year = 15 cfs

0

5

10

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

Time (minutes)

Dis

char

g




5

Outlet Structure ConfigurationOutlet Structure Configuration

Peak flow controlPeak flow control

1212--inch dia.inch dia.

Flow duration controlFlow duration control

22--inch dia.inch dia.

Not to ScaleNot to Scale

Integrating Water Quality, Flow Duration Integrating Water Quality, Flow Duration and Flood Controland Flood Control

Flow Duration Control Volume

Water Quality Volume Flood Control Volume

AgendaAgenda






FDC BasinFDC Basin

Urban Urban RunoffRunoff

BioBio--infiltration infiltration SwaleSwale

FDCFDC

FDC Integrates with LID StrategiesFDC Integrates with LID Strategies

StreamStream

FDC FDC BasinBasin

BioBio--infiltration infiltration SwaleSwale

FDC FDC VaultVault

OnOn--Site BMPsSite BMPs

LIDLID

FDC is still met at discharge point

Technical Challenges with LIDTechnical Challenges with LID

Mimicking natural hydrologic functions?

Creating the right in-stream effects?– Maintain the correct work and transport conditions?– Any unforeseen physical or ecological consequences?

i.e. extended duration of low flowsIncreased receding hydrograph and/or base flows due to increased infiltration

Developing models that everyone can use and understand– BAHM, sizing factors, sizing charts

14-inches ponded water Infiltration at 2 in/hr

Actual Et

Modeling Bioretention for LID Modeling Bioretention for LID (Excel spreadsheet model)

24-inches amended soil

6-inches gravel layer

Deep percolation to underlying soils from drainable portion only

Drainable Portion

Field Capacity

100%



6

Bioretention Model ResultsBioretention Model ResultsBio-Retention Model with QCP Discharges

400

500

600

700

u-ft)

25000

30000

35000

40000

45000

orag

e (c

u-ft)

In-Flow

Deep Percolation

Out Flow

Surface Storage

Weir discharges

0

100

200

300

11/27 11/28 11/29 11/30 12/1 12/2 12/3 12/4 12/5 12/6

Time

Flow

(cu

0

5000

10000

15000

20000

25000

Pond

Sur

face

Sto

Qcp discharges

Field capacity fills

Bioretention Model ResultsBioretention Model ResultsBio-Retention Model

(Soil Moisture: drainable plus tension)

6.0

7.0

8.0

9.0

10.0

inch

es)

0.00025

0.00030

0.00035

0.00040

s)

Soil Storage

Et

Gra

vety

Dra

in

Drainable Storage

0.0

1.0

2.0

3.0

4.0

5.0

11/8 11/18 11/28 12/8 12/18 12/28 1/7 1/17 1/27 2/6 2/16 2/26 3/8 3/18 3/28 4/7 4/17 4/27 5/7 5/17

Time

Soil

Stor

age

(i

0.00000

0.00005

0.00010

0.00015

0.00020

Et (i

nche

s

Tens

sion

Zon

e

Field Capacity

Bioretention can achieve the Bioretention can achieve the Flow Duration CriteriaFlow Duration Criteria

Flow Duration Curves

2.5

3.0

3.5

4.00%imp at 0.16 in/hr

75%imp at 0.16 in/hr

Bioretention Results

0.0

0.5

1.0

1.5

2.0

1 10 100 1000 10000

Frequency (cfs)

Flow

s (c

fs)

Summary of AREA Sizing Summary of AREA Sizing Requirements to meet the FDCRequirements to meet the FDC

LocationLocationPond (3Pond (3--ft)ft) BioretentionBioretention

Percent of Catchment

L di tLaguna Creek

Low gradientHigh resilience

Qcp = 25% (2-yr peak)7% - 9% 12% - 14%

Fairfield-SuisunMedium resilience

Qcp = 20% (2-yr peak) 9% - 11% 17% - 21%

Southern California

Sandy soils Low resilience

Qcp = 0.0010% - 14% 18% - 28%

Range of sizes dependent on catchment soil infiltration rates

Flow Duration Control VOLUME Requirements for HydromodificationTehachapi Mountains, Southern Calif.

y = 0.09843x

8.0

10.0

12.0

olum

em

ent a

rea)

Volume requirements are dependent on the change in runoff between the pre and post condition, and thus are similar regardless of control measure.

Infil=0.0Qcp=0.004 cfs/acre

y = 0.02881x

0.0

2.0

4.0

6.0

0 10 20 30 40 50 60 70 80 90 100

Percent Imperviousness

Wat

er S

tora

ge V

o(in

ches

ove

r the

cat

chm

Infil=0.16 in/hrQcp=Zero

Land RequirementsLand Requirements

BMP TypeLAND USE Total

Impervious‐ness

Soil Infiltration

Total Volume

Surface Area

Sediment Reduction

Adjustment Factor

Total Volume

Surface Area

(acres) (%) (in/hr) (ac-ft) (acres) (%) (ac-ft) (acres)

Bioretention 1.5 AC DEVELOPABLE 40.95 19 0.26 7.72 5.14 30.1 1.60 12.39 8.24Bioretention 4DU/AC 81.56 57 0.26 46.14 30.70 1.60 74.04 49.26

Basin 6DU/AC 36.61 65 0.26 23.62 8.21 1.60 37.90 13.17Basin CONFERENCE HOTEL 12.33 46 0.26 5.63 1.96 1.60 9.03 3.14Swale Minor Road 0.27 12 0.26 0.03 0.03 1.60 0.05 0.05

0.42 0.5 0.26Open 0.37 0.5 0.26Pasture 211.2 0.5 0.26PRIVATE OPEN SPACE 25.64 0.5 0.26

Swale Road (RD) 12.39 90 0.26 11.07 9.70 1.60 17.76 15.57

SLOPE / OTHER GRADED 53.83 0.5 0.26

151.2 89.4



7

Hydromodification Control Hydromodification Control IssuesIssues

Land requirements for upland hydromodification controlSignificance of ET and resulting i i i filt ti t t h fincrease in infiltration to match surface hydrology– Habitat type changes

Instream measures are discouraged or not allowed, yet may be most effective (given land use considerations/sprawl)

“Greener Channels”“Greener Channels”

Addressing Stream Addressing Stream Stability by Working Stability by Working

with the Streamwith the StreamBoulder Bed Control Structure Boulder Bed Control Structure

(back)(back)

Timber Timber StepdownStepdown (front)(front)

Advantages: These directly Advantages: These directly address the issue and both address the issue and both

existing and future developmentexisting and future development

Disadvantage: Requires Disadvantage: Requires watershed planning and watershed planning and regulatory approvals are regulatory approvals are

difficultdifficult

Questions?Questions?

contact informationestrecker@ geosyntec.com

eric strecker4

Technology