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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
Mannings Roughness Coefficients ...................................................................... 48
Blackberry (Rubus ursinus) Experiments ................................................................ 50
Blackberry Canopy and its Characteristics .......................................................... 50
Average Vertical Distributions of Flow Velocity .................................................... 53
Surface Erosion under Blackberry Canopy .......................................................... 57
Mannings Roughness Coefficients ...................................................................... 59
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
Figure 25 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow
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
Figure 27 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow
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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Figure 36 Vertical distributions of flow velocity averaged over the three replicate
blackberry canopies for flow regimes #6 (left) and #5 (right). .............................. 56
Figure 37 Vertical distributions of flow velocity averaged over the three replicate
blackberry canopies for flow regimes #8 (left) and #9 (right). .............................. 56
Figure 38 Vertical distributions of flow velocity averaged over the three replicate
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
Figure 44 Vertical distributions of flow velocity averaged over the three replicate wild
rose canopies for flow regimes #6 (left) and #5 (right). ........................................ 67
Figure 45 Vertical distributions of flow velocity averaged over the three replicate wild
rose canopies for flow regimes #8 (left) and #9 (right). ........................................ 67
Figure 46 Vertical distributions of flow velocity averaged over the three replicate wild
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;
c. Determination of the roughness coefficients associated with
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;
c. Determination of the roughness coefficients associated with
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;
c. Determination of the roughness coefficients associated with
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
8 bins with a total distance of 32 ft
bin length 4 ft
8 bins with a total distance of 32 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:
2/13/2
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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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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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
Target Flow Velocity (ft/s)
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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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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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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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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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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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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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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Figure 14 - Sandbar Willow canopy in the flume testing section before the wetting and drying
procedure.
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Figure 15 Tested Sandbar Willow canopy in the testing section, as seen after an experiment
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Table 6 - Velocity-depth Combinations for Sandbar Willow Tests
1st Sandbar Willow
Replicate Canopy
Target Flow Velocity (ft/s)
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
Target Flow Velocity (ft/s)
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
Target Flow Velocity (ft/s)
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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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 )
PR16_t00PR16_t10PR16_t20PR16_t30PR16_t40PR16_t50PR16_t60
Figure 18 - Horizontal bending of Sandbar Willow branches for run# PR16 (Vt=3ft/s
and H=5ft).
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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 )
PR18_t00PR18_t10PR18_t20PR18_t30PR18_t40PR18_t50PR18_t60
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 )
PR19_t00PR19_t10PR19_t20PR19_t30PR19_t40PR19_t50PR19_t60
Figure 20- Horizontal bending of Sandbar Willow branches for run# PR19 (Vt=6ft/s
and H=3ft).
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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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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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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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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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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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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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Mean Bending ProfileVs=5.4 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=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
Figure 25 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow Velocity
Profiles for the Mule Fat run FR18 (Vs=5.4ft/s and H=3ft)
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Mean Bending ProfileVs=6.3 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=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 )
V|x=16ftV|x=34ftV|x=47ft
Figure 26 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow Velocity
Profiles for the Mule Fat run FR19 (Vs=6.3ft/s and H=3ft)
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Mean Bending ProfileVs=4.6 ft/s H=4.5 ft
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 )
V|x=16ftV|x=34ftV|x=47ft
Figure 27 Estimated Mean Bending Profiles of Mule Fat branches and Mean Flow Velocity
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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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).
Figure 36 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 #6
and #5, respectively, where the plot on the left shows the velocity-depth combination
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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Figure 37 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 #8
and #9, respectively, where the plot on the left shows the velocity-depth combination
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).
Figure 38 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 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 )
V|x=16ftV|x=34ftV|x=47ft
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 )
V|x=16ftV|x=34ftV|x=47ft
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 )
V|x=16ftV|x=34ftV|x=47ft
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
Figure 36 Vertical distributions of flow velocity averaged over the three replicate blackberry
canopies for flow regimes #6 (left) and #5 (right).
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 )
V|x=16ftV|x=34ftV|x=47ft
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
Figure 37 Vertical distributions of flow velocity averaged over the three replicate blackberry
canopies for flow regimes #8 (left) and #9 (right).
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0
1
2
3
4
5
6
0.0 2.0 4.0 6.0