roughness study final report 2009_june-10

8/13/2019 Roughness Study Final Report 2009_June-10

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STUDY OF THE ROUGHNESS CHARACTERISTICS

OF NATIVE PLANT SPECIES

IN CALIFORNIA FLOODPLAIN WETLANDS

Report to

Department of Water Resources

State of California

by

Z.Q. Richard Chen, M. Levent Kavvas, H. Bandeh and Elcin Tan

UC Davis J.Amorocho Hydraulics Laboratory

University of California, Davis, CA 95616

John Carlon and Thomas Griggs

River Partners

Stefan Lorenzato

Division of Planning and Local assistance

California Department of Water Resources, Sacramento, CA 95816

Principal Investigator: M. Levent Kavvas

June 2009


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Table of Contents

BACKGROND ............................................................................................................... 1 Project Description .................................................................................................... 2

Contract Agreement ............................................................................................... 2

Organization and Investigation .............................................................................. 2

Project Objectives .................................................................................................. 3

Major Tasks Accomplished ....................................................................................... 3

UCDJA Hydraulics Laboratory Large Flume Facility ................................................. 5

Velocity Measurements ......................................................................................... 8

Hydraulic Head Measurements .............................................................................. 9

Video Cameras and Recording for Plant Bending Measurements ....................... 10

Soil Surface Erosion ................................................................................................ 10

Plant Bending Characteristics Under Flood Conditions ........................................... 11

Methods to Determine Hydraulic Roughness .......................................................... 12

Fish Response to Plant Canopy .............................................................................. 14

BARE SOIL EXPERIMENTS ...................................................................................... 15

Soil Composition Testing ......................................................................................... 15 Soil Cover Specimen Preparation for Flume Testing ............................................... 16

Replicate Runs and Flow Regimes ......................................................................... 18

Bare Soil Experiment Results .................................................................................. 18

PLANT CANOPY EXPERIMENTS .............................................................................. 24

Sandbar Willow (Salix exigua) Experiments ............................................................ 25

Sandbar Willow Canopy and its Bending Characteristics .................................... 25

Velocity Distributions ........................................................................................... 33

Mannings Roughness Coefficients ...................................................................... 35

Soil Surface Erosion Under Sandbar Willow Canopy .......................................... 36

Mule Fat (Baccharis salicifolia) Experiments ........................................................... 38

Mule Fat Canopy and its Bending Characteristics ............................................... 41

Velocity Distributions and Mule Fat Bending ....................................................... 41


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Soil Surface Erosion ............................................................................................ 42


Blackberry (Rubus ursinus) Experiments ................................................................ 50

Blackberry Canopy and its Characteristics .......................................................... 50

Average Vertical Distributions of Flow Velocity .................................................... 53

Surface Erosion under Blackberry Canopy .......................................................... 57


Wild Rose (Rosa californica) Experiments .............................................................. 62

Wild Rose Canopy and its Characteristics ........................................................... 62

Velocity Distributions ........................................................................................... 63

Surface Erosion under Wild Rose Canopy .......................................................... 65

Mannings Roughness Coefficients ...................................................................... 65 SUMMARY AND DISCUSSION .................................................................................. 73

REFERENCES ........................................................................................................... 76


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List of Figures

Figure 1 - Flume Setup for Roughness Study (Longitudinal Cross-section View) ......... 6

Figure 2 - Flume Setup for Roughness Study (Transactional View) ............................. 7

Figure 3 - Flume Setup for Roughness Study (Partial Plan View) ................................ 7

Figure 4 Measurement instrument and data collection setup for Roughness Study .. 8

Figure 5 - Velocity measurement locations in a cross-section ...................................... 9

Figure 6 - Prepared bare soil surface in the large flume ............................................. 17

Figure 7 - Eroded bare soil surface after the Flow Regime (V=2ft/s, H=2.5ft) ............. 17

Figure 8 - Vertical distribution of mean longitudinal flow velocity under Flow Regime

S41 (H = 2.5 ft, V = 2 ft/s) .................................................................................... 19

Figure 9 - Vertical distribution of mean longitudinal flow velocity under Flow Regime

S51 (H = 2.5 ft, V = 5 ft/s) .................................................................................... 20

Figure 10 - Longitudinal lines of hydraulic head (H) and energy head (E) in the test

section of the flume under Flow Regime S41 (H = 2.5 ft, V = 2 ft/s) .................... 21

Figure 11 Longitudinal lines of hydraulic head (H) and energy head (E) in the test

section of the flume under Flow Regime S51 (H = 2.5 ft, V = 5 ft/s) .................... 21

Figure 12 Longitudinal lines of eroded soil surface in the test section of the flume

under various Flow Regimes ............................................................................... 22

Figure 13 - Averaged Sandbar Willow Characteristics ................................................ 26 Figure 14 - Sandbar Willow canopy in the flume testing section before the wetting and

drying procedure. ................................................................................................. 27

Figure 15 Tested Sandbar Willow canopy in the testing section, as seen after an

experiment ........................................................................................................... 28

Figure 16 Sandbar Willow bending observed under a flood flow condition in the

flume. ................................................................................................................... 30

Figure 17 - Horizontal bending of Sandbar Willow branches for run# PR12 (Vt=1.5ft/s

and H=3ft). ........................................................................................................... 31

Figure 18 - Horizontal bending of Sandbar Willow branches for run# PR16 (Vt=3ft/s

and H=5ft). ........................................................................................................... 31

Figure 19- Horizontal bending of Sandbar Willow branches for run# PR18 (Vt=4.5ft/s

and H=3ft). ........................................................................................................... 32


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Figure 20- Horizontal bending of Sandbar Willow branches for run# PR19 (Vt=6ft/s

and H=3ft). ........................................................................................................... 32

Figure 21 Sandbar Willow velocity profile under various flow regimes. ..................... 34

Figure 22 - Mannings coefficients for various Sandbar Willow canopies and bare soil

surface ................................................................................................................. 35

Figure 23 - Average plant characteristics of the Mule Fat canopy obtained from the 8

patch bins (#1 to #8) for the first replicate group.................................................. 40

Figure 24 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow

Velocity Profiles for the Mule Fat run FR12 (Vs=1.3ft/s and H=3ft) ..................... 43


Velocity Profiles for the Mule Fat run FR18 (Vs=5.4ft/s and H=3ft) ..................... 44

Figure 26 Estimated Mean Bending Profiles of Mule Fat branches and Mean FlowVelocity Profiles for the Mule Fat run FR19 (Vs=6.3ft/s and H=3ft) ..................... 45


Velocity Profiles for the Mule Fat run FR16 (Vs=4.6ft/s and H=4.5ft) ................. 46

Figure 28 - Streambed elevation changes in the Mule Fat bins during the Mule Fat

(Oct-Nov) runs ..................................................................................................... 47

Figure 29 - Comparison of cumulative mean bed erosion among the Mule Fat run

groups .................................................................................................................. 47

Figure 30 - Mannings roughness coefficients as function of Reynolds number for Mule

Fat canopy, Sandbar Willow canopy, and bare soil surface ................................ 48

Figure 31 - Porosity of the blackberry canopy obtained from the 8 patch bins (#1 to

#8) of the first replicate group .............................................................................. 51

Figure 32 - Mean plant porosity of the blackberry canopy with respect to various

views, obtained from the 8 patch bins (#1 to #8) of the first replicate group ........ 52

Figure 33 - Number of blackberry branches at each bin for each of the canopy

replicates at a height of 6 inches from the soil surface ........................................ 52

Figure 34 - The mean blackberry branch diameter at 6 inches height from the soil

surface at each of the 8 bins for each of the three canopy replicates .................. 53

Figure 35 Vertical distributions of flow velocity averaged over the three replicate

blackberry canopies for flow regimes #2 (left) and #3 (right). .............................. 55


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blackberry canopies for flow regime #4. .............................................................. 57

Figure 39 Elevations at blackberry bin surface under various experimental flow

regimes with the three replicate blackberry canopies .......................................... 58

Figure 40 - Comparison of cumulative mean bed erosion among the blackberry run

groups and replicates .......................................................................................... 59

Figure 41 - Mannings roughness coefficients as function of Reynolds number under

various California native riparian vegetation canopy conditions (Sandbar Willow,Mule Fat, Blackberry canopies and bare soil surface) ......................................... 60

Figure 42 Average plant characteristics of the Wild Rose canopy obtained from the 8

patch bins (#1 to #8) of the third replicate group.................................................. 63

Figure 43 Vertical distributions of flow velocity averaged over the three replicate wild

rose canopies for flow regimes #2 (left) and #3 (right). ........................................ 66






rose canopies for flow regime #4. ........................................................................ 68

Figure 47 Elevations at blackberry bin surface under various flow regimes for the

three replicate wild rose canopies ........................................................................ 69

Figure 48 - Comparison of cumulative mean bed erosion among the wild rose run

groups .................................................................................................................. 70

Figure 49 - Mannings roughness coefficient as function of the Reynolds number under

various California native riparian vegetation canopy conditions .......................... 72

Figure 50 - Mannings roughness coefficients as function of Reynolds number under

various California native riparian vegetation canopy conditions .......................... 74


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Figure 51 - Comparison of soil surface erosion depths under different flood flow

velocities for four California native plant canopies and a bare soil surface at a

Feather River flood plain ...................................................................................... 75


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List of Tables

Table 1 - Summary of Soil Composition Analysis ....................................................... 16 Table 2 Flow Regime Combinations for 1 st Bare Soil Replicate Group .................... 18

Table 3 Flow Regime Combinations for 2 nd Bare Soil Replicate Group ................... 18

Table 4 The Sequence of the Flow Regime Tests for the Bare Soil Runs ............... 19

Table 5 - Summary of Flume Test Results for the Bare Soil Experiments .................. 23

Table 6 - Velocity-depth Combinations for Sandbar Willow Tests .............................. 29

Table 7 - Summary of Flume Test Results for Sandbar Willow Canopies ................... 37

Table 8 - Velocity-depth Combinations for Mule Fat Canopy Experiments ................. 39

Table 9 Summary Results of Mule Fat Canopy Runs .............................................. 49

Table 10 Summary Results of Blackberry Canopy Runs ......................................... 61

Table 11- Average Plant Characteristics of the Wild Rose Canopy ............................ 70

Table 12 Manning Coefficient vs Reynolds Number with the Wild Rose Canopy .... 71


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BACKGRONDToo often floodplain management and flood protection has meant the extensive

use of hard structures in the floodway such as riprap (large rock), and lining the

channel with concrete. Traditionally, the idea has been to quickly convey floodwatersand to protect neighboring property (i.e. farmland and/or urban areas). These

measures provide no ecological benefits and in many cases have proven to be costly

to maintain. The use of native vegetation in the floodplain provides (1) wetlands

habitat within the floodplain; and (2) roughness to slow floodwaters near soil surface

and, therefore, protect structures from high-velocity erosive forces.

A recent investigation (Bernhardt et al., 2005) estimated that investment in river

rehabilitation activities is approaching $1 billion per annum in the United States. The

roughness coefficient is a critical parameter in numerical hydraulic calculations, but is

commonly associated with error margins of 20% or greater (Bathurst, 2002). Hydraulic

roughness values are not known for many native floodplain plants. In contrast to

boundary friction of bare soil surface which can be defined with reasonable accuracy

by a constant value of Mannings n, the roughness of vegetation is sensitive both to

flow depth and, for flexible plants, to velocity as well. Stem flexibility is also important,

and vegetation roughness may decline by more than 50% as flow velocity increases

and stems adopt more streamlined orientations (Moghadam and Kouwen, 1997).Furthermore, as flow depth increases to submerge the plants, flow roughness declines

rapidly with a layer of unobstructed (and hence low resistance) flow developing above

the vegetation canopy (Wu et al., 1999). Therefore floodplain managers and engineers

are reluctant to use native vegetation in floodplain management, unsure of the

resulting effect on flood hydraulics and flood protection structures (i.e. levees).

Currently there is no study on the hydraulics roughness of the proposed native

California vegetation species and their impacts on the floodplain wetland environment.Improving the understanding of native floodplain plants roughness therefore have

great potential to improve the accuracy of hydraulic calculations, improve the design of

engineering structures and river rehabilitation works, and contribute to better targeted

flood management efforts. Since roughness coefficients are highly sensitive to the

presence of vegetation, with revegetation of riparian corridors proliferating throughout


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California watersheds, accurate estimation of vegetation roughness is becoming

increasingly important.

Project Description

Contract Agreement

This study was conducted by J. Amorocho Hydraulics Laboratory, Civil and

Environmental Engineering Department, University of California, Davis, under contract

No. 4600004367 between the Regents of the University of California, Davis campus

(UCD), and the California Department of Water Resources (DWR).

Organization and Investigation

Professor M. Levent Kavvas was the Principal Investigator for this study and

general direction of the project was his responsibility. DWR Technical Team headed

by Mr. Stefan Lorenzato joined the study with UCD staff, participated in frequent

review meetings and provided guidance throughout the project.

Dr. Z.Q. Richard Chen was the Senior Development Engineer of the project,

responsible for supervising the research activities of the UC Davis Hydraulics Group,

experiment designs, analyzing the experimental data and preparing project reports.

Mr. Hossein Bandeh was responsible for electrical power installation, electronic

instrumentation installations in and around the flume, collection of data, and for the

day to day operations of the flume. Mr. Mark Hannum was the technician of the

project, and, together with Ms. Emily Anderson, performed most of the modifications to

the flume apparatus. Dr. Noriaki Ohara, Dr. Mesut Cayar, Dr. Lan Liang, Ms Elcin Tan,and many other research assistances (e.g., Katherine Maher, Jimmy Pan, and

Michael) have participated in the project, and assisted in the collection and processing

of the experimental data.


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Project Objectives

Major objectives of this study are to

1. determine the hydraulic roughness (Mannings n) associated with sandbar

willow, mule fat, blackberry and wild rose riparian plant species under

various flow conditions (from low to high flows) in comparison with bare soil

roughness conditions that may be present on the floodplains in river

reaches where these plants occur;

2. determine soil erosion/deposition under the plant canopy/bare soil riverbed;

3. quantify the response of stems of the selected plant species under various

flow conditions (from low to high flows).

The purpose of this study is to provide floodplain managers and engineers with

information on the impact of native vegetations on flood flow hydraulics and

information necessary to incorporate habitat concerns and benefits into the design and

management of floodways and vegetated wetland habitats within the state of

California. The study involved point velocity raw data measurements, hydraulic head

measurements, soil erosion measurements, roughness coefficient estimations and

characterization of plant canopy response to various flow regimes.

Major Tasks AccomplishedThe following are the major tasks that have been accomplished by the

hydraulics group in this project:

1. Flume modifications and instrumentation for the roughness study project;

2. Completion of bare soil flume tests:

a. Soil composition analysis

b. Soil surface erosion measurements

c. Hydraulic measurementsd. Determination of the roughness coefficient

3. Completion of Sandbar Willow canopy flume tests:

a. Determination of Sandbar Willow plant characteristics and

Sandbar Willow branches bending under flood conditions;


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b. Soil surface erosion measurements under Sandbar Willow

canopy;

c. Determination of the roughness coefficients associated with

various flooding conditions with Sandbar Willow canopy;

4. Completion of Mule Fat canopy flume tests;

a. Determination of Mule Fat plant characteristics and Mule Fat

branches bending under flood conditions;

b. Soil surface erosion measurements under Mule Fat canopy;


various flooding conditions with Mule Fat canopy;

5. Completion of Blackberry canopy flume tests:

a. Determination of Blackberry plant characteristics;

b. Soil surface erosion measurements under Blackberry canopy;


various flooding conditions with Blackberry canopy;

6. Completion of Wild Rose canopy flume tests.

a. Determination of Wild Rose plant characteristics;

b. Soil surface erosion measurements under Wild Rose canopy;


various flooding conditions with Wild Rose canopy;


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UCDJA Hydraulics Laboratory Large Flume Facility A large flume at UCDJA Hydraulics Laboratory was used to carry out the

roughness study experimental runs. The large flume facility is shown in Figure 1,

Figure 2, Figure 3, and Figure 4. The large flume is 90 ft long, and it has 8-ft highwalls. The flume width is expandable to 32 ft, but only 4 ft width was used for this

study. Also, we constructed a false flume floor to be at the same level as the surface

level of soil in the bins. The flume sections upstream and downstream from the plant

pallets were fitted with a 2-ft high false floor. Hydraulics conditions in the flume were

controlled by the incoming flow rate, the flume entrance control at the head tank, the

height of tail tank weir and the water depth in the tail tank.

For the roughness study, a 32-ft longitudinal section of the flume was placed

with 8 bins (each with a dimension of 4 ft wide, 4 ft long and 2 ft height) containing

either bare soil or the plant species of interest. Plant canopy/soil were taken from the

flood plain within the levees of the Feather/Sacramento River, and are native

throughout California, common at both coastal and inland watersheds.

Two pumps equipped with two VFD motors were used to produce the

circulation discharge capacity of 70 cfs. The discharge is directly related to the VFD

motor rpm, which can be read directly from the motor control pane.

Two Ultrasonic Flowmeters (Mark 3) were used to measure the flowdischarges into the flume. This flowmeter measures the frequency shift of reflected

ultrasonic signal from discontinuities in the flowing fluid. These discontinuities can be

virtually any amount of suspended bubbles, solids, or interfaces caused by turbulent

flow. The flowmeter transducers are mounted externally to the pipe, thus obtaining

flow reading without process interruptions. The flowmeters were attached to the two

incoming 24 diameter pipes.

Point gauges equipped with verniers were installed on tubes that are

connected to the flume walls in order to measure the hydraulic head in the flume

channel with an accuracy of +- 0.0005 ft. The water surface fluctuation was also

monitored with a digital floater whose data were continuously recorded during the

experiments.


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4 ft bin Width

Flume width 5 ft

8 ft

6 ft

2 ft

4 ft bin Width

Flume width 5 ft

8 ft

6 ft

2 ft

Figure 2 - Flume Setup for Roughness Study (Transactional View)

8 bins with a total distance of 32 ft

bin length 4 ft

4ft


bin length 4 ft


bin length 4 ft

4ft

Figure 3 - Flume Setup for Roughness Study (Partial Plan View)

Two data collection computers were installed on a carriage on top of the

flume, as shown in Figure 4. One computer controlled the ADV probe and stored the

collected velocity data. The other computer controlled the digital floaters and stored

the collected hydraulic head data. Velocity values, measured by the ADV probe, were

recorded into a computer data file for a selected time period, with a measurement

frequency of 0.1 Hz to 25 hertz (Hz). The data from the digital floaters could also be

recorded into a computer data file for a selected time period.


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Figure 4 Measurement instrument and data collection setup for Roughness Study

Velocity Measurements

A SonTek ADV (Acoustic Doppler Velocimeter) down-looking probe was used

to measure point location water velocities in the flume and a computer was used to

record and store the measured data. The general procedures for a point velocity

measurement were in accordance with the SonTeks user guide for ADV probe, the

measuring equipment that was used for the point velocity measurements. The range

for the point velocity measurements was set at 0-8 ft/s. The sampling frequency of the

ADV probe was set at 10 Hz, and the time period of velocity recording for each point

was 30 seconds. The measurements started when the flow in flume stabilized near

the target velocity and the target depth.

For each average depth - average velocity combination (flow regime) the pointlocation velocities were measured at three cross-sections that are at upstream,

downstream and mid-section of the plant patch (the center of the first bin, the center of

the test section, and the center of the 8 th bin). In order to obtain the mean velocity

values at the three cross-sections in the flume, multiple points were sampled at each


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of these flow cross-sections. At each of these cross-sections, the five vertical velocity

profiles at 5 horizontal locations between the two flume walls were measured. For

each vertical velocity profile, point location velocities were measured at five depths.

Therefore there were 25 measurements of point location velocity for a flow cross-

section, as shown in Figure 5.

4 ft bin Width

Flume width 5 ft

8 ft

6 ft

2 ft

4 ft bin Width

Flume width 5 ft

8 ft

6 ft

2 ft

4 ft bin Width

Flume width 5 ft

8 ft

6 ft

2 ft

Figure 5 - Velocity measurement locations in a cross-section

Hydraulic Head Measurements

Point gauges/digital floaters were used to measure the hydraulic head in the

flume. Hydraulic heads that were measured by potential meters (floaters), were

recorded and stored in a computer. The hydraulic head readings from point gauges

were recorded on paper by hand. The sampling frequency of the digital floaters was

set at 10 Hz and the time period of recording for each point was set at 5 minutes.

Hydraulic heads were measured at three cross-sections along the longitudinal

direction, one being upstream of the plant patch section, one at downstream of the

plant patch section, and one location at the center of the plant patch section (the

center of the first bin, the center of the test section, and the center of the 8 th bin),


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separated 14 ft apart. The hydraulic head measurements were taken four times in a

run, i.e., one time when the flow in the flume stabilizes near the target velocity and the

target depth at the beginning of the run, and 3 times after the velocity measurements

at each of the 3 flow cross-sections were completed.

Calibration of the point gauges reference elevation and calibration of the

floaters at the beginning or at the end of a run were carried out for each run. The

accuracy of the point gauge readings is +- 0.0005 ft.

Video Cameras and Recording for Plant Bending Measurements

In order to measure the bending displacements of the plant stems, measuring

tapes were pasted to the south flume walls in the horizontal direction with a 1-ft

vertical interval at the plant patch section of the Flume at several depths along the

range of stem heights, corresponding to a plant species canopy. Furthermore, a total

of 12 monitoring video cameras were installed in the north flume wall along the placed

plant patch section of the Flume at three depths, i.e., at 1 ft, 2.5 ft and 4 ft depths from

the channel bed. Then through the 12 viewing cameras, the behavior of the plants

with respect to their bending, and possible failure, and the possible soil movement

corresponding to each of the flow regimes were monitored by a TV display. Video

images from the 12 cameras, which were sequentially mixed with a video recordermultiplexer, were recorded into a video tape for about 3 minutes at the beginning of

each test. After a test run, the mixed video images in the video tape were replayed

through the multiplexer and were captured as 12 separated clips of digital video for

each of the 12 video cameras in a computer. The digital video clips were saved as

AVI formatted files and video capture software was used for this operation.

Soil Surface Erosion A SonTek ADV probe was used to measure point soil surface elevation in the

Flume, and a computer was used to display the reading. The readings of the soil

surface elevation were recorded at the beginning of the test before running the water,

and at the end of the test after the flow stopped. The point soil surface elevation

measurements were taken cross-sectionally at 5 locations at each center of the 8 bins.


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Methods to Determine Hydraulic RoughnessThe total effect of all roughness elements to stream flow is usually combined

into a single-valued parameter called a stream roughness coefficient for hydraulic

computations. There are three kinds of roughness coefficients, i.e., the Chezy C, theMannings n, and the Darcy-Weisbach f, each of which is essentially interchangeable

with the others. Determination of roughness coefficient is central to both simple and

sophisticated hydraulic analyses. Yet it remains encumbered with the greatest level of

uncertainty of all hydraulic parameters.

While the contribution of vegetation to flow resistance is known to be the

important component in many streams, few vegetation roughness estimation

techniques are available. Plant structures are challenging to describe numerically

because of their myriad of shapes, structures, and the mosaic of their distributions

along rivers. The magnitude of the roughness coefficient depends principally on the

density and stiffness of the plant structures. The roughness of vegetation is sensitive

both to flow depth and, for flexible plants, to velocity as well.

The Mannings roughness value n is commonly used to account for the

resistance to flow presented by stream channel. In a strict sense, Mannings n and the

other one-dimensional friction loss parameters should be used to account only for that

part of the losses arising from the frictional resistance along the channel boundary, i.e.the effects of various roughness elements and small scale irregularities of the

boundary (Kadlec, 1990). Higher Mannings roughness n values correspond to

rougher channels. Lower n values are associated with channels with smoother

boundary materials and lower sinuosity. Appropriate values for n are typically

estimated based on tables for n, developed through empirical study.

Mannings n is selected as the roughness coefficient for the plant canopy/bare

soil surface in this study. Calculating n in this study follows the commonly used

method as described by Chow (1959) and others.

Mannings equation relates flow velocity (V) to the flow cross-sectional area (A),

the flow perimeter (P), and the friction slope (S) as follows:

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49.1S

P A

nV

= (1)


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where V = cross-sectionally-averaged velocity (ft/s)

n = Mannings roughness coefficient

A = cross-sectional area (ft 2)

P = wetted perimeter (ft)

S = friction slope (ft/ft)

Note that:

=

P A

Rh (2)

where R h is referred to as the hydraulic radius.

Rearranging Equation (1) to determine the Mannings roughness coefficient for

the whole flume cross-section:

( ) 2/13/249.1 S RV

n h= (3)

Mannings equation assumes steady and uniform flow. When the velocity at any given

point remains constant with respect to time, then flow is considered steady. If flow

depth does not change with location along the channel, then the flow is uniform. Since

the flows in the flume were not exactly steady and uniform, averaged values over the

test section of the flume were used for variables R h , V and S in Equation (3).

Since the effect of the flume wall on the Mannings coefficients is relatively

small for a plant canopy, it is assumed that the flume Mannings coefficients,

computed by Equation (3), are equivalent to the Mannings roughness coefficients of

the particular plant canopy. It is important to mention that within the rectangular flume

cross-section of the experimental setup, the hydraulic radius is a direct function of the

flow depth. Since the Mannings roughness coefficient changes with flow depth and

velocity (F.M.Henderson, Open Channel Flow, 1966), the Mannings roughness

coefficient for a specified plant species and specified average depth average

velocity conditions was plotted as a function of the Reynolds Number (Re) and theplant canopy/surface cover.

In this study the velocity and hydraulic head measurements were used to

determine the mean velocity, the mean water depth and the mean hydraulic radius in

the flume. The velocity head profile was determined from the cross-sectionally-


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averaged velocity measurements at three specified sections in the bare soil patch

section. The water surface profile was determined from measuring hydraulic heads

along the longitudinal direction of the flume within the test section. Friction slopes

were determined from the measured water surface profile and velocity head profile

under each average depth average velocity combination.

Fish Response to Plant Canopy An experiment to study the fish response to the Sandbar Willow canopy was

carried out. Different from the hydraulic testing configuration, a mesh screen at the

downstream of the flume was installed for the fish experiment with the Sandbar Willow

canopy. The results of the fish experiment study are discussed in a separate report.


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BARE SOIL EXPERIMENTS

Soil Composition TestingIn order to investigate the characteristics of the soil samples in the study, a soil

sample test was carried out. A total of 10 bins of soil were collected from the habitat

restoration areas on the floodplain of the Feather River. Among the 10 bins, 8 bins

were selected for flume test. The other two bins were used to fill the selected 8 bins

for level adjustment.

A simple soil survey of the soil texture composition was carried out in order to

find out how the soil composition varies among the soil samples that were used in the

experiment and the soil in the habitat restoration area. Summary results of the soil

composition test are shown in Table 1. The Bare Soil Bins refer to the samples

delivered to the UCDJA Hydraulics Lab on August 11, 2006. The Rose Bins refer to

the samples removed from the wooden crates containing wild rose specimens stored

at the Feather River site just off of the levee road. The Trail along the Feather river

refers to samples removed from areas prevalent in wild rose just off the trail that

follows the Feather River. Each sample was a 2 diameter core to a depth of 15.

Three samples were taken from each of the three sites.The test results showed that the Bare Soil Bins contained barely half of the

percentage of the sand in the Rose Bins, a percentage difference of 41% with respect

to sand content. The Trail site was closer in percentage to that of the Rose Bins, with

an 18.3 difference with respect to silt content. The Bare Soil Bins and Rose Bins have

a difference of 26.6%. TheTrail site differed from the Bare Soil Bins by 8%. The

difference between the Bare Soil Bins and Rose Bins was 14.3%. The Trail site

differed by 11.3%. The samples taken from both the Rose Bins and the Trail site both

exceeded the +10% acceptable percentage difference between samples (as

described by the Department of Water Resources). From these test results it may be

inferred that the Bare Soil Bin samples that were delivered to the UCDJA Hydraulics

Laboratory do not contain the same soil that is present at the Rose Bins or the Trail

Site Bins.


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Table 1 - Summary of Soil Composition Analysis

Sample Location Average Sand % Average Silt % Average Clay %

Bare Soil Bins 43.7 36.3 20

Rose Bins 84.7 9.7 5.7

Trail along

Feather River62 28.3 9.7

(Note: The Hard Pan Soil sample was ignored as it could not be taken with the

same coring device as the other three, and was therefore not comparable)

Soil Cover Specimen Preparation for Flume TestingIn order to have consistent topsoil cover in the flume, the bare soil bins were

first filled with soil that originated from the same location, up to the edges of the bin

box. The bins were then saturated with water after being installed into the flume, until

the time when the release of the bubbles stopped. Then the ponded water over the

bins was discharged from the flume and the soil in the bins was let to settle andcompact as it dried. We continued the repeated wetting-and-drying process two times

before the beginning of each flow experiment. The prepared bare soil surface in the

large flume is shown in Figure 6. After a flow experiment within the flume when water

passed over the bins, a realistic bare soil streambed formed in the flume, as shown in

Figure 7.


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17

Figure 6 - Prepared bare soil surface in the large flume

Figure 7 - Eroded bare soil surface after the Flow Regime (V=2ft/s, H=2.5ft)


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18

Replicate Runs and Flow RegimesThe bare soil experiment runs were conducted under various target flow

regimes, as shown in Table 2 and Table 3. A combination of target flow velocity andtarget flow depth is defined as a flow regime. After each soil experiment run, the

depth-velocity combination was adjusted to one of the combinations that are shown in

Tables 2 and 3, repeating this process until all of the combinations were exhausted.

Table 2 Flow Regime Combinations for 1 st Bare Soil Replicate Group

1st Bare Soil

Replicate Group

Target Flow Velocity (ft/s)

1.0 2.0 5.0

Target Flow

Depth (ft)

5.5 S11

5.2 S21

2.5 S31 S41 S51

1.0 S61 S71

Table 3 Flow Regime Combinations for 2 nd Bare Soil Replicate Group

2nd Bare Soil

Replicate Group


1.5 3.0 4.5

Target Flow

Depth (ft)

5.0 R23 R26

3.0 R22 R25 R28

1.5 R21 R24

Bare Soil Experiment ResultsTwo replicate groups were studied for the bare soil surface. The first replicate group of

soil bins was used for the flow regimes listed in Table 2, while the second replicate

group of soil bins was used for the flow regimes listed in Table 3. A total of 14

hydraulic tests for the two replicate groups of bare soil bins were carried out in


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20

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0 10 20 30 40 50 60 70

X [ft]

E l e v a

t i o n

[ f t ]

Water Surface Flume Top Elevation Bottom Elevation

Velocity at P#2 Velocity at P#3 Velocity at P#4

V= 2 ft/s

Figure 9 - Vertical distribution of mean longitudinal flow velocity under Flow Regime S51 (H =

2.5 ft, V = 5 ft/s)

Energy head line in the flume

The hydraulic head readings from point gauges were recorded at the three flow

cross-sections shown in Figure 8 and Figure 9. The hydraulic head readings were

recorded in three different times during a flow regime run. Digital water surface

elevation that was measured by potential meters (floaters), was recorded. Due to thelow accuracy of the potential meters, the digital water surface elevation data were not

used in the analysis of the energy head in this study. The averaged values of the

hydraulic head were used to determine the flow depth and the hydraulic radius of the

flume cross-section. The mean flow velocity in the flume was computed using the

measured velocity distribution, as shown in Figure 8 and Figure 9. For a specified

flow regime the friction slope in the testing section of the flume was computed based

on the average slope of the energy head line, as shown in Figure 10 and Figure 11.

Mannings roughness coefficients for bare soil surface

Finally, Mannings coefficients for the soil surface were calculated by Equation

(3) with the measured mean velocity and estimated friction slope and hydraulic radius

for each flow regime.


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21

Soil Erosion for bare soil surface

The soil surface elevations were measured by a SonTek probe at the beginning

of a test before running the water, and at the end of the test after the flow had

stopped. Figure 12 shows the eroded soil surface elevations in the test section of the

flume for the flow regimes for which the measurements were available although a total

of 14 test runs for the soil bare surface were conducted.

S41(H=2.5,V=2ft/s)

2.542.552.562.572.582.59

2.62.612.62

15 20 25 30 35 40 45 50x(ft)

f tE= (H + hv)

H(Point Gage)

Figure 10 - Longitudinal lines of hydraulic head (H) and energy head (E) in the test section of the

flume under Flow Regime S41 (H = 2.5 ft, V = 2 ft/s)

S51(H=2.5ft, V=5 ft/s)

2.5

2.6

2.7

2.8

2.9

3

15 20 25 30 35 40 45 50

x(ft)

f t

E= (H + hv)H (Point Gage)

Figure 11 Longitudinal lines of hydraulic head (H) and energy head (E) in the test section of

the flume under Flow Regime S51 (H = 2.5 ft, V = 5 ft/s)


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22

Eroded Soil Surface2.01.00.0

1.02.03.04.05.06.07.08.0

18.0 23.0 28.0 33.0 38.0 43.0 48.0X(ft)

Z ( i n

)

R23 R22 R21 R26R25 R24 R28 R29R2i S51

Figure 12 Longitudinal lines of eroded soil surface in the test section of the flume under

various Flow Regimes


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23

Table 5 - Summary of Flume Test Results for the Bare Soil Experiments

R e p l i c a t e G

r o u p

FlowRegime

IDDate

T a r g e t H

T a r g e t V

MeasuredEnergy

LineGradient

MeasuredMeanWaterDepth

MeasuredMean

Velocity

MeasuredMean

SurfaceVelocity

ReynoldsNumber

(Re)

Manning'sRoughnessCoefficient

for Bare Soil(n)

MannRough

Coefffor Bar

HorMeth

(ns

(ft) (ft/s) (ft/ft) (ft) (ft/s) ft/s S11 10/19/2006 5.5 1.0 0.000089 5.51 0.94 0.91 135442 0.0198 0.0S31 10/20/2006 2.5 1.0 0.000146 2.50 0.99 1.00 107253 0.0198 0.0S61 10/24/2006 1.0 1.0 0.000143 1.00 0.96 1.01 61697 0.0143 0.0S21 10/26/2006 5.2 2.0 0.000280 5.16 1.95 2.06 276095 0.0167 0.0S41 10/30/2006 2.5 2.0 0.000276 2.61 1.87 1.96 207153 0.0145 0.0S71 11/1/2006 1.0 2.0 0.000711 1.00 1.84 1.95 118924 0.0167 0.0

S51 11/2/2006 2.5 5.0 0.002221 2.58 4.20 4.65 461967 0.0185 0.0R23 12/7/2006 5.0 1.5 0.000127 4.98 1.56 1.54 218751 0.0138 0.0R22 12/8/2006 3.0 1.5 0.000153 3.00 1.52 1.60 178659 0.0137 0.0R21 12/11/2006 1.5 1.5 0.000342 1.53 1.58 1.70 132747 0.0158 0.0R26 12/11/2006 3.0 5.0 0.000968 4.71 3.12 3.36 430255 0.0188 0.0R25 12/12/2006 3.0 3.0 0.000524 2.93 2.97 3.27 345080 0.0130 0.0R24 12/13/2006 1.5 3.0 0.001246 1.49 2.92 3.18 241821 0.0162 0.0R28 12/14/2006 3.0 4.5 0.002765 2.88 4.52 4.66 522361 0.0194 0.0

2 n d r e p l i c a t e

b a r e s o i l s u r f a c e

1 s t r e p l i c a t e

b a r e s o i l s u r f a c e


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24

PLANT CANOPY EXPERIMENTSIn this study four California native vegetation canopies, i.e. Sandbar Willow,

Mule Fat, Blackberry, and Wild Rose, were tested in the large flume.

The plant characteristics of the four canopies were quantified differently andwere measured using different statistics. For each of the plant canopy experimental

runs, the flow regimes were selected from the combinations of three different water

flow depths and 3-4 different flow velocities. The three water depths for plant canopy

runs were selected as 1.5 ft, 3 ft and 5 ft. The velocities ranged from 1.5 ft/s to 7.0 ft/s.

Two of the selected plant species, i.e., Sandbar Willow and Mule Fat, were tested for

their stem/branch response to selected flow regimes. The bending characteristics of

the plant stems of Sandbar Willow and Mule Fat were measured in terms of

displacement at different heights. Similar to the bare soil surface testing, erosion of the

surface soil under all of the four plant canopies were determined by measuring directly

the soil surface elevations before the experiment and after the flow stopped for each

experiment run by means of a Sontek ADV Probe which is capable of detecting the

soil surface elevation. Finally, Mannings coefficients for the plant canopies were

calculated by Equation (3) with the measured mean velocity, and estimated friction

slopes and hydraulic radius for each flow regime.

In the following sections, the results of the flume tests for the four plantcanopies will be presented.


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26

computer. Through the viewing cameras along the test section of the flume, the

behavior of the Sandbar Willow canopy with respect to their bending, and possible

failure, and the possible soil movement corresponding to each of the flow regimes

were recorded. The individual frames for each video image that depict the

stem/branch positions were digitized. From the analysis of the digitized images, the

bending displacements of the individual plant stems within a plant patch were

estimated at selected elevations from the ground surface to the top of the range of the

stem/branch heights (0.5ft, 1.0ft, 1.5ft, etc). Then at the selected elevations from the

ground surface to the top of the range of stem/branch heights the stem/branch

displacements were averaged over the stems/branches that were present in the 12

camera viewing windows in order to determine the bending characteristics of the plant

patch under the particular flow regime. Figure 16 shows the mean bending of theSandbar Willow branches as observed in the testing section of the flume.

0

1

2

3

4

5

6

0 2 4 6 8

D e p

t h ( f t )

Number of Branches Per SQFT

Plant Blockage Width (in)

Mean Diameter (in)

Figure 13 - Averaged Sandbar Willow Characteristics


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27

Figure 14 - Sandbar Willow canopy in the flume testing section before the wetting and drying

procedure.


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28

Figure 15 Tested Sandbar Willow canopy in the testing section, as seen after an experiment


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29

Table 6 - Velocity-depth Combinations for Sandbar Willow Tests

1st Sandbar Willow

Replicate Canopy


1.5 3.0 4.5 6.0 7.0

Flow

Depth

(ft)

5.0 PR13 PR16

3.0 PR12 PR15 PR18 PR19 PR17

1.5 PR11 PR14

2nd Sandbar Willow

Replicate Canopy


1.5 3.0 4.5 6.0 7.0

Flow

Depth

(ft)

5.0 PR23 PR26

3.0 PR22 PR25 PR28 PR29

1.5 PR21 PR24

3 rd Sandbar Willow

Replicate Canopy


1.5 3.0 4.5 6.0 7.0

Flow

Depth

(ft)

5.0 PR33 PR36

3.0 PR32 PR35 PR38 PR39

1.5 PR31 PR34

Note: a tested flow regime in the table is shown as P R x n where P indicates the

Sandbar Willow canopy experiment, R x indicates the replicate number, and n

indicates a flow velocity-depth combination id. P and x can be replaced based the

type of plant canopy and the replicate number of the runs. For example, for P

identifying a Sandbar Willow experiment, R2 denoting the replicate #2, and 8

denoting the flow velocity-depth combination with a target water depth H=3.0 ft and a

target flow velocity V=4.5 ft, the resulting flow regime id is PR28.


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0.0

0.5

1.0

1.5

2.0

2.5

0.0 2.0 4.0 6.0

Bending Displacement (in)

D e p

t h (

f t )

V=1.5 ft/s & H=5 ft

Figure 16 Sandbar Willow bending observed under a flood flow condition in the flume.

Figures 17, 18, 19, and 20 show the mean bending of the Sandbar Willow

branches as function of height above the flume false floor surface at various times (0,

10, 20, 30, 40, 50, 60 seconds) in the first minute of the flume test under the flow

regimes PR12, PR16, PR 18 and PR 19, respectively.


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31

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-5 -4 -3 -2 -1 0Horizontal Bending (ft)

H e

i g t h ( f t )

PR12_t00PR12_t10PR12_t20PR12_t30PR12_t40PR12_t50PR12_t60

Figure 17 - Horizontal bending of Sandbar Willow branches for run# PR12 (Vt=1.5ft/s

and H=3ft).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-5 -4 -3 -2 -1 0Horizontal Bending (ft)

H e

i g t h ( f t )


Figure 18 - Horizontal bending of Sandbar Willow branches for run# PR16 (Vt=3ft/s

and H=5ft).


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32

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-5 -4 -3 -2 -1 0

Horizontal Bending (ft )

H e

i g t h ( f t )


Figure 19- Horizontal bending of Sandbar Willow branches for run# PR18 (Vt=4.5ft/s

and H=3ft).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-5 -4 -3 -2 -1 0Horizontal Bending (ft )

H e

i g t h ( f t )


Figure 20- Horizontal bending of Sandbar Willow branches for run# PR19 (Vt=6ft/s

and H=3ft).


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34

0

1

2

3

4

5

0 2 4 6Velocity (ft/s)

Z ( f t )

V|x=16ft

V|x=34ftV|x=47ft

0

1

2

3

4

5

0 2 4 6Velocity (ft/s)

Z ( f t )

V|x=16ft

V|x=34ftV|x=47ft

V=4.5 ft/s H=3 ft V=6.0 ft/s H=3 ft

Velocity Profile /Sandbar Willow

0

1

2

3

4

5

0 2 4 6Veloci ty (ft/s)

Z ( f t )

V|x=16ft

V|x=34ftV|x=47ft

0

1

2

3

4

5

0 2 4 6Veloci ty (ft/s)

Z ( f t )

V|x=16ft

V|x=34ftV|x=47ft

V=1.5 ft/s H=5 ft V=3.0 ft/s H=5 ft

Velocity Profile /Sandbar Willow

Figure 21 Sandbar Willow velocity profile under various flow regimes.


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35

Mannings Roughness Coefficients

The hydraulic head readings from point gauges were taken at 3 flow cross-sections

within the Sandbar Willow canopy (the center of the first bin, the center of the testsection, and the center of the 8th bin), and at one flow cross-section at the

downstream end of the canopy at 5 different times during a 3.5 hours test period after

the mean velocity and the water depth in the flume stabilized near the target velocity

and the target depth. The energy line and the friction slope under each flow regime

were estimated using the measured hydraulic head and velocity head.

Mannings coefficients for Sandbar Willow canopy roughness were calculated

based on the quality-controlled data using Equation (3). A comparison of the

Mannings roughness coefficients for Sandbar Willow canopy and for bare soil surface

is shown in Figure 22.

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0 100,000 200,000 300,000 400,000 500,000 600,000 700,000

Re

M

a n n i n g

' s n

Sandbar Willow (March)

Sandbar Willow (April)

Sandbar Willow (May)

Bare Soil

Linear (Sandbar Willow (March))

Linear (Sandbar Willow (April))

Linear (Sandbar Willow (May))

Linear (Bare Soil )

Figure 22 - Mannings coefficient for various Sandbar Willow canopies and bare soil surface

The results of the three replicates of Sandbar Willow runs indicated that the

Mannings roughness coefficients for the Sandbar Willow canopies varied with flow

velocity, flow depth, plant growth stages, plant bending characteristics and Reynolds

number of the flow.


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Soil Surface Erosion Under Sandbar Willow Canopy

Erosion of the soil of the streambed was estimated based on the surface

elevations before and after a flume test run. A SonTek ADV probe and a computer

were used to measure the soil surface elevations at 40 point locations within the

Sandbar Willow bins. The soil surface elevations at the middle of each of the 8

Sandbar Willow bins were measured at 5 horizontal transverse measurement points

by a SonTek probe at the beginning of the test before running the water, and at the

end of the test after the flow had stopped. Mean eroded soil depths listed in Table 7

were obtained from the measured soil surface elevation values.


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Table 7 - Summary of Flume Test Results for Sandbar Willow Canopies

ReplicateRun

Order

FlowRegime

ID Date T a r g e

t H

T a r g e

t V MeasuredEnergy

Line Slope

MeasuredMeanWaterDepth

MeasuredMean

Velocity

MeasuredMean

SurfaceVelocity

ReN

(ft) (ft/s) (ft/ft) (ft) (ft/s) (ft/s)01 Pr13 3/1/2007 5.0 1.5 0.00089 5.00 1.51 1.98 209,72902 Pr12 3/5/2007 3.0 1.5 0.00152 2.99 1.32 1.76 152,25503 Pr11 3/6/2007 1.5 1.5 0.00248 1.48 1.19 1.39 95,54804 Pr16 3/12/2007 5.0 3.0 0.00274 4.65 2.91 3.84 394,17305 Pr15 3/13/2007 3.0 3.0 0.00447 2.84 2.72 3.82 306,51906 Pr14 3/14/2007 1.5 3.0 0.00786 1.53 2.16 2.65 177,11607 Pr18 3/19/2007 3.0 4.5 0.00752 2.83 4.00 5.72 448,99608 Pr19 3/21/2007 3.0 6.0 0.00969 2.84 4.48 6.31 504,62309 Pr17 3/22/2007 3.0 7.0 0.00832 3.26 5.24 7.06 624,765

01 Pr23 4/17/2007 5.0 1.5 0.00111 4.99 1.41 2.16 197,75702 Pr22 4/18/2007 3.0 1.5 0.00260 3.00 1.23 1.56 144,16103 Pr21 4/19/2007 1.5 1.5 0.00309 1.54 1.04 1.19 87,90504 Pr26 4/25/2007 5.0 3.0 0.00469 4.69 2.66 3.78 366,86505 Pr25 4/26/2007 3.0 3.0 0.00743 2.97 2.42 3.55 283,36206 Pr24 4/30/2007 1.5 3.0 0.01108 1.67 1.95 2.34 172,73907 Pr28 5/1/2007 3.0 4.5 0.01196 2.97 3.50 5.72 409,06408 Pr29 5/2/2007 3.0 4.5 0.01508 2.91 4.02 6.21 466,142

01 Pr33 5/15/2007 5.0 1.5 0.00229 5.01 1.30 1.94 183,150

02 Pr32 5/16/2007 3.0 1.5 0.00322 2.99 1.20 1.48 140,78503 Pr31 5/17/2007 1.5 1.5 0.00354 1.50 1.09 1.22 90,60004 Pr36 5/21/2007 5.0 3.0 0.00545 4.72 2.63 4.21 363,12105 Pr35 5/22/2007 3.0 3.0 0.00850 2.98 2.20 3.18 258,25506 Pr34 5/23/2007 1.5 3.0 0.01127 1.69 1.85 2.20 164,73807 Pr38 5/29/2007 3.0 4.5 0.01549 3.01 3.22 4.94 378,18508 Pr39 5/30/2007 3.0 4.5 0.01683 2.95 4.07 6.54 474,836

S a n

d b a r

W i l l o w

( M a r c h

)

S a n

d b a r

W i l l o w

( A p r

i l )

S a n

d b a r

W i l l o w

( M a y

)


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38

Mule Fat (Baccharis salicifolia) ExperimentsThe Mule Fat runs were conducted during October 2007 to Feb 2008. A total of 24

bins of Mule Fat canopy were used in the experiments, and they were divided into 3

groups for three replicates. Canopy characterization data for each experimental patch

of Mule Fat were collected in terms of stem/branch density, stem/branch diameter,

and overall heights of individual plants, as shown in Figure 23. Extra soil was added

to the top of each bin so that the wooden edges of the bin were covered by soil, and

wetting/drying of the bins were performed 2 times after the bins were installed in the

flume.

A total of 30 flume test runs were carried out with Mule Fat canopies. Four groups

of runs were conducted with the 3 replicates of Mule Fat canopies. Table 8 lists the

velocity-depth combinations that were used for the Mule Fat canopy experiments. The

first replicate Mule Fat canopy was used in a total of 14 flume test runs, which were

processed in terms of two groups (Oct-Nov) and (Nov-Dec). As indicated in Table 8,

some of the first replicate canopy runs were repeated in the second group. The

reasons for this repetition were that the downstream end boundary conditions in theflume were altered for fish testing, and that a VFD controller for the large flume pumps

was damaged and had to be replaced. The soil erosion measurements were not made

during the (Nov-Dec) runs in order to catch up with the experimental schedule. The

second replicate Mule Fat canopy was used in a total of 8 flume test runs, shown as

the group (January) in Table 8. The third replicate Mule Fat canopy was also used in a

total of 8 flume runs, shown as the group (February) in Table 8.


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0.00

1.00

2.00

3.00

4.00

5.00

6.00

0.00 2.00 4.00 6.00 8.00

H e i g

h t ( f t )

Number of Branches Per SQFT

Plant Blockage Width (in)

Mean Diameter (in)

Figure 23 - Average plant characteristics of the Mule Fat canopy obtained from the 8 patch bins

(#1 to #8) for the first replicate group


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41

Mule Fat Canopy and its Bending Characteristics

In order to measure the bending displacements of the Mule Fat

branches/stems, a total of 12 monitoring video cameras were installed into the

Flumes north wall along the placed plant patch section of the Flume at three depths,

at 1 ft, 2.5 ft and 4 ft from the channel bed. Then through the 12 viewing cameras, the

behavior of the plants with respect to their bending, and possible failure, and the

possible soil movement corresponding to each of the flow regimes were monitored in

a TV display. Video images from the 12 cameras were recorded into a video tape at

the beginning of each test. The video images in the video tape were replayed and

were captured as separate clips of digital video for each of the 12 video cameras in a

computer. The individual frames for each video image that depict the stems/branches

positions were digitized. From the analysis of the digitized images, the bending

displacements of individual plant stems within a plant patch were estimated at

selected elevations from the flume bed surface to the top of the range of stem/branch

heights (0.5ft, 1.0ft, 1.5ft, etc). Then at the selected elevations from the flume bed

surface the stem/branch displacements were averaged over the stems/branches

present in the 12 camera viewing windows in order to determine the bending

characteristics of the plant patch under the particular flow regime.

Velocity Distributions and Mule Fat Bending

During each of the flow tests a SonTek ADV (Acoustic Doppler Velocimeter) down-

looking probe was used to measure the point location flow velocity in the flume, and a

computer was used to record and store the measured data. For each average depth -

average velocity combination (flow regime) the point location velocities were

measured at five selected longitudinal cross-sections at 16 ft, 19 ft, 34 ft, 47 ft and 51

ft at upstream and mid-section of the plant patch (the center of the first bin, the center

of the test section, and the center of the 8th bin) and downstream of the patch section.

In order to obtain the mean velocity values at the three cross-sections in the flume,

multiple points were sampled at each of these flow cross-sections. At each of these

cross-sections, five vertical velocity profiles at 5 horizontal locations between the two


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42

flume walls were measured. For each vertical velocity profile, the point location

velocity was measured at four or five depths depending on the flow regime. The time

duration for velocity recordings was set to 30 seconds at each location point. The

collected point velocity data were analyzed later with the WinADV software program in

order to obtain the mean velocity at each point location.

Once the mean flow velocities at all the point locations were obtained, using the

WinADV, the mean flow velocity at each measurement depth at the five selected

longitudinal cross-sections was estimated by averaging the mean point velocities at

each depth. Then, the vertical distributions of the mean flow velocity at the selected

longitudinal locations were obtained.

Figure 24, 25, 26, and 27 show the vertical distributions of the mean flowvelocity and the bending profile of the Mule Fat branches/stems, estimated from the

values measured in flume tests under the flow regimes FR12, FR18, FR 19 and FR

16, respectively. These figures were constructed in order to show the interaction

between the water flow and the plant bending. In Figure 24, 25, 26, and 27, the

bending profiles at various times indicate that the plant responds to the water flow

within about 30 seconds, and then oscillates around its new bending position. They

also indicate that the bending occurs mostly at the top of the plant canopy, and the

higher the velocity is the more bending the plant performs. The velocity profiles at the

three longitudinal locations (upstream of the plant canopy, the middle section of the

canopy and the downstream end of the canopy) indicate that the plant reduces the

flow velocity within the canopy and speeds it up above the canopy.

Soil Surface Erosion

Erosion of the streambed soil was estimated based on the surface elevations

that were measured at the beginning and end of the flume test runs. A SonTek ADV

probe and a computer were used to measure the soil surface elevations at 40 point

locations within the Mule Fat bins. There are 5 elevation locations in each of the 8 bins

within the flume, which were averaged to obtain the mean elevation for each bin.

Figure 28 shows the elevation changes in the streambed during the Mule Fat (Oct-


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43

Nov) runs. The cumulative mean erosion during the Mule Fat (Oct-Nov) runs, the Mule

Fat (January) runs, and the Mule Fat (February) runs are shown in Figure 29.

Mean Bending ProfileVs=1.3 ft/s H=3.0 ft

0

0.5

1

1.5

2

2.5

3

-4 -3 -2 -1 0Horizontal Relative Bending (ft)

H e

i g t h ( f t )

t=00st=10st=20st=30s

t=40st=50st=60s

0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft /s)

h e i g h t ( f t )

V|x=16ftV|x=34ft

V|x=47ft

Figure 24 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow Velocity

Profiles for the Mule Fat run FR12 (Vs=1.3ft/s and H=3ft)


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44


0

0.5

1

1.5

2

2.5

3

-4 -3 -2 -1 0Horizontal Relative Bending (ft )

H e i g t

h ( f t )

t=00s

t=10s

t=20s

t=30s

t=40s

t=50s

t=60s

0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft/s)

h e

i g h t ( f t )

V|x=16ftV|x=34ftV|x=47ft




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45


0

0.5

1

1.5

2

2.5

3

-4 -3 -2 -1 0Horizontal Relative Bending (ft)

H e

i g t h ( f t )

t=00st=10st=20st=30st=40st=50st=60s

0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft/s)

h e

i g h t ( f t )





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0

0.5

1

1.5

2

2.5

3

3.5

4

-4 -3 -2 -1 0

Horizontal Relative Bending (ft)

H e i g t

h ( f t )

t=00st=10s

t=20st=30s

t=40s

t=50st=60s

0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft/s)

h e

i g h t ( f t )



Profiles for the Mule Fat run FR16 (Vs=4.6ft/s and H=4.5ft)


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Mannings Roughness Coefficients

The Mannings n roughness coefficient values for the Mule Fat canopy were estimated

based on the measured mean total energy line gradient of equilibrium flow within the

flume. The mean cross-sectional flow velocity heads were estimated using the vertical

distributions of velocity at 19 ft, 34 ft and 47 ft longitudinal locations along the flume.

The mean water surface elevations in the flume were obtained by using the point

gauge measurements of pressure head at the bottom of the flume wall at longitudinal

locations19 ft, 34 ft and 47 ft along the flume. The energy line gradient was computed

using measurements of the velocity head and the mean surface elevation. Figure 30

shows a summary and comparison of the estimated Mannings roughness coefficient

values for Mule Fat canopy, Sandbar Willow canopy, and bare soil surface.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0 100,000 200,000 300,000 400,000 500,000 600,000 700,000

Re

M

a n n

i n g

' s n

Sandbar Willow (March)

Sandbar Willow (April)

Sandbar Willow (May)

Mule Fat (Oct-Nov)

Mule Fat (Nov-Dec)

Mule Fat (January)

Mule Fat (February)

Bare Soil

Linear (Sandbar Willow (March))

Linear (Sandbar Willow (April))

Linear (Sandbar Willow (May))

Linear (Mule Fat (Oct-Nov) )

Linear (Mule Fat (Nov-Dec))Linear (Mule Fat (January))

Linear (Mule Fat (February))

Linear (Bare Soil )

Figure 30 - Mannings roughness coefficient as function of Reynolds number for Mule Fat

canopy, Sandbar Willow canopy, and bare soil surface


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Table 9 Summary Results of Mule Fat Canopy Runs

R e p

l i c a

t e

G r o u p

RunNumber

FlowRegime

ID Date T a r g e t

H

T a r g e t

V

MeasuredEnergy

Line Slope

Measured

MeanWaterDepth

MeasuredMean

Velocity

Measured

MeanSurfaceVelocity

ReynoldsNumber

(Re)

Mann

RoughCoeff

((ft) (ft/s) (ft/ft) t t s t s

1 MR13 10/23/2007 5.00 1.50 0.0041 4.99 1.17 1.53 164161 0.1044 02 MR12 10/25/2007 3.00 1.50 0.0053 3.23 1.11 1.38 133983 0.1136 3 MR11 10/26/2007 1.50 1.50 0.0044 1.92 1.03 1.17 98499 0.0946 4 MR16 10/30/2007 5.00 3.00 0.0067 4.78 2.33 4.36 323303 0.0662 05 MR15 10/31/2007 3.00 3.00 0.0103 3.03 1.68 1.83 198117 0.1022 06 MR14 11/1/2007 1.50 3.00 0.0126 1.93 1.64 1.71 156483 0.1008 7 MR18 11/5/2007 3.00 4.50 0.0052 3.00 2.19 3.00 256931 0.0559 8 MR19 11/7/2007 3.35 6.00 0.0134 3.32 2.72 3.46 332262 0.0739 9 FR18 11/13/2007 3.00 4.50 0.0177 3.07 3.17 5.48 376255 0.0713

10 FR19 11/14/2007 3.35 6.00 0.0216 3.04 4.03 6.36 475654 0.0619 11 FR12 12/14/2007 3.00 1.50 0.0044 2.93 1.09 1.32 127051 0.1013 12 FR16 12/17/2007 5.00 3.00 0.0067 4.71 2.69 4.59 371459 0.0573 13 FR15 12/18/2007 3.00 3.00 0.0108 2.94 2.21 3.13 257117 0.0793 14 FR14 12/27/2007 1.50 3.00 0.0131 1.67 1.86 1.96 164158 0.0862

1 FR23 1/16/2008 5.00 1.50 0.0034 4.94 1.32 1.87 184767 0.0844 02 FR22 1/17/2008 3.00 1.50 0.0053 2.96 1.18 1.30 137357 0.1044 03 FR21 1/18/2008 1.50 1.50 0.0049 1.56 0.97 0.86 82168 0.0986 4 FR26 1/23/2008 5.00 3.00 0.0072 4.78 2.64 4.55 366156 0.0605 05 FR25 1/24/2008 3.00 3.00 0.0112 3.06 2.12 2.86 250954 0.0850 06 FR24 1/25/2008 1.50 3.00 0.0092 2.12 1.25 1.33 125010 0.1167 07 FR28 1/28/2008 3.00 4.50 0.0180 3.12 3.18 5.20 380206 0.0720 08 FR29 1/29/2008 3.35 6.00 0.0108 2.95 3.89 5.74 454100 0.0448 0

1 FR33 2/12/2008 5.00 1.50 0.0032 5.01 1.32 2.07 186295 0.0815 02 FR32 2/13/2008 3.00 1.50 0.0050 3.01 1.17 1.43 137775 0.1022 03 FR31 2/14/2008 1.50 1.50 0.0050 1.50 0.98 0.99 81878 0.0968 4 FR36 2/15/2008 5.00 3.00 0.0072 4.74 2.63 4.71 363460 0.0611 5 FR35 2/18/2008 3.00 3.00 0.0112 3.06 2.12 2.96 251138 0.0848 06 FR34 2/19/2008 1.50 3.00 0.0156 1.80 1.75 2.08 161333 0.1027 07 FR38 2/20/2008 3.00 4.50 0.0178 3.11 3.05 5.29 363676 0.0746 08 FR39 2/21/2008 3.35 6.00 0.0198 3.28 3.36 6.43 409234 0.0724 0

February

Oct-Nov

Nov-Dec

January


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Blackberry (Rubus ursinus) Experiments

This section of the report describes the results that were obtained from theBlackberry Canopy Experiments.

Blackberry Canopy and its Characteristics

Prior to the start of the Blackberry canopy flume experiments, a total of 24

patch bins of Blackberry were obtained from the River Partners. The Blackberry

patches were divided into 3 replicate groups with 8 patch bins in each group. Similar

to the flume tests done for other plants, a group of 8 Blackberry bins were installed

into the test section of the flume for each replicate experiment. A wetting/drying

procedure was performed 2 times to consolidate the soil in the bins and to prepare the

canopy for the flow tests in the flume.

Blackberry branches/stems grow into very complicated patterns that are very

different from the Sandbar Willow and the Mule Fat. Due to this complexity, the plant

characteristics of the Blackberry canopy were quantified in terms of the visual porosity

measurements that may be defined by

)()()( _

vreaTotalViewAviedArea PlantOccupvreaTotalViewAvity PlantPoros

=

where v denotes the view directions that include 1) view from the east (upstream), 2)

view from the west (downstream), 3) view from the north, 4) view from the south, and

5) view from the top of the plant patches. The plant porosity values for the 8 bins of

the first Blackberry replicate group are presented in Figure 31. The mean porosity

values are shown in Figure 32.

Each of the plant canopies were cut at 6 inches height from the soil surfaceafter they were used in the flume roughness hydraulic experiments. Then for this fixed

height the plant density (number of branches/16 sqft bin area) were measured

manually. The number of branches at 6 inches height in each of the bins for each of

the plant canopy replicates is shown in Figure 33. After the canopy was cut at 6 inches

height, the branch diameters were also measured manually. The mean blackberry


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52

0

10

20

30

40

50

60

70

Upstream Downstream North South Top

M e a n

P o r s i t y

( % )

Figure 32 - Mean plant porosity of the blackberry canopy with respect to various views, obtained

from the 8 patch bins (#1 to #8) of the first replicate group

Bin # 1

Bin # 2

Bin # 3

Bin # 4

Bin # 5

Bin # 6

Bin # 7

Bin # 8

Replicate#1

Replicate#2

Replicate#3

0

10

20

30

40

50

60

N u m

b e r o

f

B r a n c h e s

Replicate#1

Replicate#2

Replicate#3

Figure 33 - Number of blackberry branches at each bin for each of the canopy replicates at a

height of 6 inches from the soil surface


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Bin # 1

Bin # 2

Bin # 3

Bin # 4

Bin # 5

Bin # 6

Bin # 7

Bin # 8

Replicate#1

Replicate#2

Replicate#3

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

M e a n

B r a n c h

D i a m e t e r

( i n

)

Replicate#1

Replicate#2

Replicate#3

Figure 34 - The mean blackberry branch diameter at 6 inches height from the soil surface at

each of the 8 bins for each of the three canopy replicates

Average Vertical Distributions of Flow Velocity

A total of 24 flume test runs were carried out with three replicate blackberry

canopies and velocity-depth combinations that are listed in Table 10. Each of the

replicate blackberry canopies was constructed with 8 blackberry bins. In Table 10, the

first replicate canopy is denoted as BR_Mar#1, the second as BR_Apr#2, and the

third as BR_May#3. Each replicate canopy was used for 8 different velocity-depth

combination test runs. During a flow test a SonTek ADV (Acoustic Doppler

Velocimeter) down-looking probe was used to measure point-location flow velocity in


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the flume, and a computer was used to record and store the measured data. For each

flow regime (depth-velocity combination) the point-location velocities were measured

at five selected longitudinal cross-sections at 16 ft, 19 ft, 34 ft, 47 ft and 51 ft at the

upstream and the mid-section of the plant patches (the center of the first bin, the

center of the test section, and the center of the 8th bin) and at the downstream. In

order to obtain the mean velocity values at the three cross-sections in the flume,

multiple points were sampled at each of these flow cross-sections. At each of these

cross-sections, the five vertical velocity profiles at 5 horizontal locations between the

two flume walls were measured. For each vertical velocity profile, point-location

velocity was measured at four or five depths depending on the flow regime. The

duration for each velocity recording was set to 30 seconds at each location point. The

collected point velocity data were analyzed later with the WinADV software program inorder to obtain an estimate of the mean flow velocity at each point location.

Once the mean flow velocities at all the point locations were estimated, using

the WinADV, the mean velocity at each measurement depth at the five selected

longitudinal cross-sections was estimated by averaging the mean point velocities at

each depth. Then, the vertical distributions of mean flow velocity at the selected

longitudinal locations were obtained.

Figure 35 shows comparisons of the vertical distributions of mean flow velocity,

estimated from the values measured in the flume tests, averaged under the same

target flow regimes from the three replicate blackberry canopies for flow regimes #2

and #3, respectively, where the plot on the left shows the velocity-depth combination

of Vt =1.5ft/s, Ht =3ft (BR12, BR22, and BR32), and the plot on the right shows the

velocity-depth combination of Vt =1.5ft/s and Ht= 5ft (BR13, BR23, and BR33).





of Vt=3ft/s and Ht=5ft (BR16, BR26, and BR36) and the plot on the right shows the

velocity-depth combination of Vt=3ft/s and Ht=3ft (BR15, BR25, and BR35).


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of Vt=4.5ft/s and Ht=3ft (BR18, BR28, and BR38) and the plot on the right shows the

velocity-depth combination of Vt=6ft/s and Ht=3.4ft (BR19, BR29, and BR39).



target flow regime (Vt=3ft/s and Ht=1.5ft) from the three replicate blackberry canopies

for the flow regime #4 (BR14, BR24, and BR34).

These figures were constructed in order to show the interaction between the

water flow and the plant bending. The flow velocity profiles at the three longitudinallocations (upstream of the plant canopy, the middle section of the canopy and the

downstream end of the canopy) indicate that the plant reduces the flow velocity within

the canopy and speeds it up above the canopy.

0

1

2

3

4

5

6

0.0 2.0 4.0 6.0Velocity (ft/s)

h e

i g h t ( f t )


0

1

2

3

4

5

6

0.0 2.0 4.0 6.0Velocity (ft/s)

H e

i g h t ( f t )


Figure 35 Vertical distributions of flow velocity averaged over the three replicate blackberry

canopies for flow regimes #2 (left) and #3 (right).


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0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft/s)

H e i g h

t ( f t )


0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft /s)

H e i g h

t ( f t )




0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (f t/s)

H e i g h

t ( f t )


0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

Velocity (ft/s)

H e i g h

t ( f t )





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0

1

2

3

4

5

6

0.0 2.0 4.0 6.0

roughness study final report 2009_june-10

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