gerrard rainbow spawning habitat assessmenta100.gov.bc.ca/appsdata/acat/documents/r6875/gerra... ·...

Gerrard Rainbow Spawning Habitat Assessment

Water depth and velocity over the main spawning gravels on the Lardeau River during low flows

April 17, 2006

Gerrard Rainbow Spawning Habitat Assessment

Water depth and velocity over the main spawning gravels on the Lardeau River during low flows

Prepared for:

BC Ministry of Environment (MoE)Nelson

by:

Joseph Thorley106 Richards St.Nelson V1L 5J5

BC

and

Jason Bowers520 Wasson St.

Nelson V1L 3G7BC

April 17, 2006

This project was funded by BC Environment’s Habitat Conservation Trust Fund (HCTF). The Habitat Conservation Trust Fund was created by an act of the legislature to preserve, restore and enhance key areas of habitat for fish and wildlife throughout British Columbia. Hunters, anglers, trappers and guides contribute to the Trust Fund enhancement projects through license surcharges. Tax deductible donations to assist in the work of the Trust Fund are welcome

Suggested Citation: Thorley, J.L. and Bowers J. 2006. Gerrard Rainbow Spawning Habitat Assessment: Water depth and velocity over the main spawning gravels on the Lardeau Riverduring low flows. Report prepared for BC Ministry of the Environment, Nelson. 10 p. + 3 app.

i

Acknowledgements

The following people are gratefully acknowledged for contributions of information and assistance during this study

BC Ministry of Environment

Jeff Burrows, Senior Fisheries Biologist – NelsonColin Spence, Fisheries Research Biologist – NelsonJohn Bell, Fisheries Biologist – NelsonAlbert Chirico, Fish Habitat/Inventory Specialist – Nelson

BC Ministry of Agriculture and Lands

Vern Vogt, Geomatic Services– VictoriaAli Kharaghani, Geomatic Services- Victoria

ii

Executive Summary

The Gerrard rainbow trout (Oncorhynchus mykiss) of Kootenay Lake, spawn in a restricted area of gravels in the Lardeau River. Due to the confinement of Mobbs Creek, a junction bar has formed across the Lardeau River downstream of the spawning site. The bar acts like a dam raising the height of the water over the gravels and reducing the velocity. There is concern that the gravels may become unsuitable for spawning.

To allow historical and future comparisons we measured the water depth and water velocity at 2.5 m intervals along 10 transects running across the main spawning gravels. During low flows, the depth of water over most of the gravels exceeds 1 m. The depth of water over the gravels has increased by between 0.6 and 1.0 m since 1966-1967. The water velocity 0.2 m above the gravels is now typically 0.1 to 0.2 ms-1 compared to 0.3 to 0.7 ms-1 forty years ago.

iii

Table of Contents

Acknowledgements.......................................................................................................................... iExecutive Summary ........................................................................................................................ iiTable of Contents........................................................................................................................... iiiList of Tables ................................................................................................................................. ivList of Figures ................................................................................................................................ ivBackground..................................................................................................................................... 1Objectives ....................................................................................................................................... 1Materials and Methods.................................................................................................................... 2

Area surveyed ............................................................................................................................. 2Endpoints .................................................................................................................................... 2GPS positions.............................................................................................................................. 2Transects ..................................................................................................................................... 3Water depth and velocity ............................................................................................................ 3Discharge .................................................................................................................................... 3Gravel samples............................................................................................................................ 4

Results............................................................................................................................................. 5GPS positions.............................................................................................................................. 5Discharge .................................................................................................................................... 6Gravel samples............................................................................................................................ 6Water depth and velocity ............................................................................................................ 6

Discussion ....................................................................................................................................... 8GPS positions.............................................................................................................................. 8Water velocity............................................................................................................................. 8Water depth................................................................................................................................. 8Gravel samples............................................................................................................................ 8

Conclusions..................................................................................................................................... 9References..................................................................................................................................... 10Appendix A - Tabulated data........................................................................................................ 11Appendix B - Water depths and velocities for each of the ten transects. ..................................... 19Appendix C – Photographs ........................................................................................................... 22

iv

List of Tables

Table 1. The configuration of the GPS precision settings. ............................................................ 2Table 2. The configuration of the GPS coordinate settings........................................................... 2Table 3. The calculated discharge for each transect (m3s-1) ....................................................... 11Table 4. The final, fully-corrected easting and northing for each of the GPS positions. ............ 12

Table 5. The measured distances (m) and declination-corrected bearings between pairs of GPS positions. ............................................................................................................................... 13

Table 6. The measured water depths (m) and velocities (ms-1) for all the transect points with calculated northings and eastings. V0.2m is the water velocity 0.2 m above the gravels (ms-

1) and VMean is the mean column water velocity (ms-1). ..................................................... 14

List of Figures

Figure 1. A map of the differentially-corrected GPS positions. The long narrow polygon with the horizontal stripes represents the bridge and the short wide polygon with the vertical stripes the viewing platform.................................................................................................... 5

Figure 2. Trend surface of water depth (m)................................................................................... 6Figure 3. Trend surface of water velocity 0.2 m above gravels (ms-1). ......................................... 7Figure 4. Trend surface of mean column water velocity (ms-1). .................................................... 7

Figure 5. The water depth (m) and velocities (ms-1) along transects 1-5 moving from the south to north bank. The depth is indicated by the solid line, the velocity 0.2 m above the gravels (ms-1) by the triangles and the mean column velocity by the circles (ms-1). ......................... 19



1

Background

The Gerrard rainbow trout of Kootenay Lake, are a distinct population of piscivorous rainbow trout (Oncorhynchus mykiss) with individuals that grow to over 12 kg in weight. Every spring, Gerrard rainbow trout ascend the Lardeau River to spawn in a restricted area of gravels below the outlet of Trout Lake (Hartman and Galbraith, 1970).

The spawning gravels were deposited in the Lardeau River by Mobbs Creek. Prior to human interference, Mobbs Creek distributed its gravels over the bed of the Lardeau River in the form of an alluvial fan (nhc, 2002). Mobbs Creek has since been trained and confined into a single channel that passes under a bridge before entering the Lardeau River approximately 500 m downstream from the outlet of Trout Lake. Due to its confinement Mobbs Creek has been depositing its bedload as a junction bar across the Lardeau River (nhc, 2002).

The anthropogenic alterations to the morphology of the Mobbs Creek channel have caused a number of changes to the spawning gravels. In particular the aggradation of the junction bar has caused an increase in water depth and a decrease in water velocity over the gravels (nhc, 2003). In addition, flood events on Mobbs Creek have caused temporary reversals of flow in the Lardeau River and the deposition of fine sediments onto the spawning gravels (nhc, 2002). The anthropogenic changes to the hydromorphology of the Mobbs Creek-Lardeau River confluence have led to concerns that the gravels below the outflow of Trout Lake may become unsuitable for spawning Gerrard rainbow trout.

This report describes a field study that was conducted to measure the water depth, water velocity, and streambed particle sizes in the Lardeau River in the main spawning area during low flow conditions. The discussion includes a comparison with the depths and velocities recorded historically.

Objectives

The scope of the study included the following:

Measure water depth and mean column water velocity and near-bottom water velocity at a series of regularly spaced points (over 200 points) on the main spawning gravels (approximately 25 m above the Gerrard bridge to approximately 75 m below).

Record the location of each reading and substrate sample using a hand-held GPS.

2

Materials and Methods

Area surveyedThe main spawning gravels run from approximately 25 m above the Gerrard bridge to 75 m below. The depth and water velocities were recorded along 10 transects running across the river. The transects were positioned approximately 10 m apart below the bridge and approximately 20m apart above the bridge. The area of gravels surveyed corresponds to the area between transects A to G in Figure 4 of Hartman and Galbraith (1970).

EndpointsThe endpoints of each transects were marked by a 3 foot piece of rebar hammered into the frozen river-bank or a dead tree-trunk. The location of each endpoint was photographed using a digital camera (Appendix C). In addition, the distance and bearing between adjacent endpoints on the same bank and between endpoints on the same transect were recorded using a field tape measure and handheld sighting compass. All bearings were corrected by 17° E for declination.

GPS positionsThe position of each transect endpoint, as well as the position of the bench mark BM 480 H, and the four corners of the bridge and viewing platform were recorded every second for at least two minutes from the Coarse/Acquistion (C/A) code of the available satellites using a handheld Trimble® GeoExplorer 3 Global Positioning System (GPS) unit (BC MELP, 2001). The configurations of the GPS precision and coordinate settings are listed in Tables 1 and 2.

Table 1. The configuration of the GPS precision settings.

Setting ValuePositional Dilution Of Precision (PDOP) mask 5.0

Signal to Noise Ratio (SNR) mask 6.0Elevation mask 15°

Minimum satellites 4

Table 2. The configuration of the GPS coordinate settings

Setting ValueSystem Universal Transverse Mercator

Zone 11 NorthDatum NAD 1983 (Canada)

Altitude Reference MSLGeoid DMA 10x10 (Global)

Coordinate Units MetersAltitude Units Meters

3

The GPS positions were differentially corrected, post-collection, using the Trimble GPS Pathfinder Office 2.51 software and data from the Invermere base station. The Invermere base station is approximately 90 km from the field site.

The GPS positions of the endpoints were further adjusted so that i) the distance between the GPS positions of each pair of endpoints in a transect was identical to the measured distance between the actual endpoints; ii) the bearing between the GPS positions of the two endpoints in a transect remained constant and iii) the GPS positions of the pair of endpoints in a transect were adjusted by the same amount. The adjustments were made using the free statistical software package R 2.2.1 (R Development Core Team, 2005). The easting and northing of each of the measurement points on each transect were then calculated from the eastings and northings of the endpoints. The final, fully corrected eastings and northings for all the GPS positions including the measurement points are tabulated in Appendix A.

TransectsA 12 mm dynamic rope was stretched between the rebar marking the endpoint for each transect. A 60 m field tape measure was fixed to the rope by zap straps. In water deeper than approximately 1.2 m the depth and velocity measurements were taken from a flat-bottomed aluminium boat attached to the rope. The water depth and water velocities were recorded at 2.5m intervals along each transect.

Water depth and velocityThe water depth was measured using a wooden depth pole with a steel end. The water velocities were recorded using a Marsh-McBirney, Inc. Flo-Mate™ Model 2000 Portable Flowmeter. The flowmeter was zero checked at the beginning and end of the study. The sensor was attached to a mount positioned 0.2 m from the end of the depth pole and the cable fixed to the depth pole using zap straps. The flowmeter determined the water velocity using fixed point averaging (FPA) with a five second period. The recorded velocity is the rounded average of at least three readings. More than three readings were taken if the displayed velocity was unstable until the field crew deemed the rounded average of all the readings to be representative of the mean velocity.

The water velocity was recorded 0.2 m above the river bottom. If the water was greater than 0.8m deep the water velocity was also recorded at 0.8 and 0.2 of the depth since in deeper water the average of these two measurements is a reliable estimate of the mean column velocity (BC MWLAP 1998). Alternatively, if the water was less than 0.8 m deep the water velocity wasrecorded at 0.6 of the water depth since this single measurement provides a reliable estimate of the mean column velocity in shallower water (BC MWLAP 1998).

DischargeThe river height on the staff gauge fell from 3 cm below the zero mark at 15:00 hr on the 14th of December 2005 to 5 cm below at 15:51 hr on the 16th of December 2005. At 13:07 hr on the 17th

4

of December the river height was still 5 cm below the zero mark. On the 24th of March 2006 the river height was approximately 20 cm below the zero mark. The river flow at each transect was calculated from the depths and mean column water velocities.

Gravel samplesWe attempted to take gravel samples using a McNeil core and shovel (BCMWLAP, 2002).

5

Results

GPS positionsMapping the differentially-corrected GPS positions (Figure 1) indicated that they fell within the 2 m or 5 m accuracy classes (BCMELP, 2001).

Easting (480km)

No

rth

ing

(5

59

5km

)

375 400 425 450 475

30

03

25

35

03

75

40

04

25

BMBM

BMBM

BM

1N2N

4N

5N 6N7N 8N

9N10N 11N

1S

2S4S 5S 6S

7S8S 9S

10S 11S

BMBM

BMBM

BM

1N2N

4N

5N 6N7N 8N

9N10N 11N

1S

2S4S 5S 6S

7S8S 9S

10S 11S

50m

N

Figure 1. A map of the differentially-corrected GPS positions. The long narrow polygon with the horizontal stripesrepresents the bridge and the short wide polygon with the vertical stripes the viewing platform.

6

DischargeConsidering all ten transects the mean discharge between the 15th and 17th of December was 8.7 m3s-1 with 95% confidence intervals of ±0.23 m3s-1. The calculated discharges for each transect are tabulated in Appendix A.

Gravel samplesDue to the depth of water over the gravels, which in all the suitable sites exceeded 0.5 m, we were unable to take representative samples using the McNeil core or shovel.

Water depth and velocityTo give an indication of the spatial variation in depth and velocities a polynomial least-squares regression trend surface of degree 4 was fitted to the depth and velocity data (Venables and Ripley, 2002). The individual transects are plotted in Appendix B.

Easting (480km)

No

rth

ing

(5

59

5km

)

375 400 425 450 475

30

03

25

35

03

75

40

04

25

BM

1N 2N

4N

5N 6N7N 8N 9N 10N 11N

1S

2S4S

5S 6S

7S 8S 9S 10S 11S

50m

N

Figure 2. Trend surface of water depth (m).

7

Easting (480km)

No

rth

ing

(5

59

5km

)

375 400 425 450 475

30

03

25

35

03

75

40

04

25

BM

1N 2N

4N

5N 6N7N 8N 9N 10N 11N

1S

2S4S

5S 6S

7S 8S 9S 10S 11S

50m

N

Figure 3. Trend surface of water velocity 0.2 m above gravels (ms-1).

Easting (480km)

No

rth

ing

(5

59

5km

)

375 400 425 450 475

30

03

25

35

03

75

40

04

25

BM

1N 2N

4N

5N 6N7N 8N 9N 10N 11N

1S

2S4S

5S 6S

7S 8S 9S 10S 11S

50m

N

Figure 4. Trend surface of mean column water velocity (ms-1).

8

Discussion

GPS positionsAlthough accuracy to the 1 m level can be achieved with a high-end hand-held GPS unit, the observed accuracy of between 2 and 5 m is typical for the Trimble GeoExplorer 3 (BCMELP, 2001). Higher-resolution mapping of the gravels using GPS would require a dual receiver relative positioning system such as that used by Brasington et al. (2000).

Water velocityThe water velocities 0.2 m above the gravels were substantially lower than the velocities recorded by Hartman and Galbraith (1970) during low flows (c.10 m3s-1) in their 1966-1967 survey. Forty years ago the water velocity 0.2 m above the gravels during low flows was greater than 0.3 ms-1 over most of the spawning gravels and faster than 0.5 ms-1 over much of it. In some areas the velocity was more than 0.9 ms-1 (Hartman and Galbraith 1970, Figure 12). In December 2005, at a flow of about 8.7 m3s-1, the fastest velocity 0.2 m above the gravels was just 0.23 m3s-1 and the velocity over much of the area was less than 0.18 ms-1. In December 2005, the mean column water velocities were less than 0.18 ms-1 over much of the gravels. Comparison with the historical mean column velocities was not possible since Hartman and Galbraith (1970) do not report the mean column velocities and the historical survey data were not available.

The reduction in water velocity may be cause for concern. Hartman and Galbraith (1970, p.46) in their discussion of habitat use observe that in the most heavily used spawning area “where water velocities 20 cm above bottom fell below 30 cm per second at low water, the gravel was not used, even in periods of high water when velocities are 50 to 70 cm per second.” However,this observation may merely reflect the fact that the trout tend to select raised areas of the gravels as nest sites (Hartman and Galbraith, 1970).

Water depthThe water depth over the main spawning gravels during low flows has increased by between 0.6 and 1.0 m since 1966-1967. The increase in depth was established by measuring the depth along the edge of a small bay 20 m to the west of the bridge on the north bank. In Hartman and Galbraith’s (1970) Figure 4 the same bay was mapped as being dry during low flows.

Gravel samplesThe depth of water over the river bed prevented collection of gravels for fine sediment analysis using a McNeil core or shovel. The recently developed SÉDIBAC sampler (Lachance and Dubé, 2004) may provide a relatively inexpensive method to quantify the fine sediment composition of the gravels. Installation and removal of the samplers would require a wet or dry suit and snorkelling equipment. Freezing-coring may provide a more accurate but more expensive method for sampling the gravels (BC MWLAP, 2002). As with the SÉDIBAC , the basic methodology would have to be adapted to deal with the depth of water over the gravels.

9

Conclusions

During low flows, the depth of water over most of the gravels exceeds 1.0 m. The depth of water over the gravels has increased by between 0.6 and 1.0 m since 1966-1967. The water velocity 0.2 m above the gravels is now typically 0.1 to 0.2 ms-1 compared to 0.3 to 0.7 ms-1 forty years ago.

10

References

BC Ministry of Water, Land and Air Protection. 1998. Manual of Standard Operating Procedures for Hydrometric Surveys in British Columbia. Version 1. Prepared for Resources Inventory Committee.

BC Ministry of Environment, Land and Parks. 2001. British Columbia Standards, Specification and Guidelines for Resource Surveys Using Global Positioning Systems (GPS) Technology. Release 3.0.

BC Ministry of Water, Land and Air Protection. 2002. Guidelines for Monitoring Fine Sediment Deposition in Streams. Field Test Edition. Version 1.3. Prepared for Resource Information and Standards Committee.

Brasington, J, Rumsey, BT and McVey, RA. 2000. Monitoring and modelling morphological change in a braided gravel-bed river using high resolution GPS-based survey. Earth Surface Processes and Landforms, 25: 973-990.

Hartman, GF and Galbraith DM. 1970. The reproductive environment of the Gerrard stock rainbow trout. Fisheries Management Publication No. 15.

Lachance, S and Dubé M. 2004. A new tool for measuring sediment accumulation with minimal loss of fines. North American Journal of Fisheries Management 24: 303-310.

northwest hydraulic consultants (nhc). 2002. Mobbs Creek Geomorphic Assessment. Prepared for BC Ministry of Water, Land and Air Protection.

northwest hydraulic consultants (nhc). 2003. Mobbs Creek – Lardeau River hydraulic modelling and assessment. Prepared for BC Ministry of Water, Land and Air Protection.

R Development Core Team. 2005. R: A language and environment for statistical computing. Vienna, Austria. (http://www.R-project.org)

Venables, WN and Ripley BD. 2002. Modern Applied Statistics with S. Fourth Edition. Springer, New York.

11

Appendix A - Tabulated data

Table 3. The calculated discharge for each transect (m3s-1)

Transect Discharge1 8.472 8.134 8.965 9.126 9.017 8.748 9.199 8.29

10 8.5311 8.83

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Table 4. The final, fully-corrected easting and northing for each of the GPS positions.

Point Bank Easting NorthingBM North 480447.39 5595372.90

1 North 480391.67 5595392.361 South 480363.36 5595338.432 North 480406.66 5595394.322 South 480384.17 5595324.474 North 480429.00 5595377.244 South 480412.73 5595321.635 North 480433.75 5595371.065 South 480422.25 5595319.046 North 480441.19 5595370.976 South 480432.61 5595319.437 North 480444.99 5595367.997 South 480444.13 5595313.658 North 480452.77 5595368.218 South 480452.64 5595315.919 North 480461.32 5595368.919 South 480463.86 5595316.96

10 North 480471.42 5595369.1510 South 480471.61 5595319.2511 North 480479.66 5595369.2911 South 480481.33 5595319.34

Platform1 North 480453.12 5595371.90Platform2 North 480470.28 5595372.57Platform3 North 480465.77 5595384.18Platform4 North 480453.66 5595378.64

Bridge1 North 480428.78 5595388.20Bridge2 North 480425.22 5595387.87Bridge3 South 480401.92 5595320.13Bridge4 South 480407.02 5595318.33

13

Table 5. The measured distances (m) and declination-corrected bearings between pairs of GPS positions.

From ToPoint Bank Point Bank Distance Bearing

1 South 1 North 60.91 29°2 South 2 North 73.38 19°4 South 4 North 57.95 NA5 South 5 North 53.28 11°6 South 6 North 52.24 7°7 South 7 North 54.35 3°8 South 8 North 52.30 357°9 South 9 North 52.01 358°

10 South 10 North 49.90 0°11 South 11 North 49.98 359°1 South 2 South 22.80 NA2 South Bridge* South 19.80 304°

Bridge* South 4 South 10.85 279°3 South 4 South 12.70 289°4 South 5 South 10.15 279°5 South 6 South 9.70 264°6 South 7 South 11.35 292°7 South 8 South 10.90 255°8 South 9 South 10.15 263°9 South 10 South 10.00 253°

10 South 11 South 10.00 267°1 North 2 North 14.15 256°2 North 3 North 18.00 307°3 North 4 North 11.25 301°4 North 5 North 6.85 315°5 North 6 North 6.90 278°6 North 7 North 4.45 290°7 North 8 North 7.50 267°8 North 9 North 8.55 263°9 North 10 North 10.95 267°

10 North 11 North 7.55 268°BM South 6 North 8.65 48°BM South Platform** North 5.91 310°

* Orange mark on south-west side of bridge** North-east corner of viewing platform

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Table 6. The measured water depths (m) and velocities (ms-1) for all the transect points with calculated northings and eastings. V0.2m is the water velocity 0.2 m above the gravels (ms-1) and VMean is the mean column water

velocity (ms-1).

Transect Distance Depth V0.2m VMean Easting Northing1 5.33 0.00 NA NA 480365.84 5595343.151 6.03 0.11 NA NA 480366.17 5595343.771 8.53 0.34 0.04 0.03 480367.33 5595345.981 11.03 0.59 0.05 0.05 480368.49 5595348.201 13.53 0.78 0.09 0.10 480369.65 5595350.411 16.03 0.95 0.07 0.12 480370.81 5595352.621 18.53 1.04 0.10 0.15 480371.97 5595354.841 21.03 1.13 0.11 0.14 480373.14 5595357.051 23.53 1.09 0.12 0.12 480374.30 5595359.261 26.03 1.14 0.08 0.09 480375.46 5595361.481 28.53 1.31 0.08 0.11 480376.62 5595363.691 31.03 1.44 0.12 0.15 480377.78 5595365.901 33.53 1.55 0.17 0.17 480378.94 5595368.121 36.03 1.55 0.18 0.19 480380.11 5595370.331 38.53 1.71 0.18 0.19 480381.27 5595372.551 41.03 1.80 0.14 0.18 480382.43 5595374.761 43.53 1.77 0.14 0.16 480383.59 5595376.971 46.03 1.54 0.14 0.16 480384.75 5595379.191 48.53 1.17 0.16 0.18 480385.92 5595381.401 51.03 0.85 0.21 0.19 480387.08 5595383.611 53.53 0.62 0.19 0.19 480388.24 5595385.831 56.03 0.33 0.11 0.08 480389.40 5595388.041 57.93 0.00 NA NA 480390.28 5595389.722 4.40 0.00 NA NA 480385.52 5595328.662 5.95 0.19 NA NA 480385.99 5595330.132 8.45 0.41 0.01 0.03 480386.76 5595332.512 10.95 0.49 0.07 0.06 480387.53 5595334.892 13.45 0.56 0.09 0.10 480388.29 5595337.272 15.95 0.73 0.09 0.10 480389.06 5595339.652 18.45 0.80 0.12 0.12 480389.82 5595342.032 20.95 0.77 0.12 0.13 480390.59 5595344.412 23.45 0.92 0.08 0.11 480391.36 5595346.792 25.95 1.10 0.12 0.12 480392.12 5595349.172 28.45 1.12 0.08 0.11 480392.89 5595351.552 30.95 1.12 0.12 0.17 480393.66 5595353.932 33.45 1.07 0.23 0.22 480394.42 5595356.312 35.95 1.22 0.22 0.20 480395.19 5595358.692 38.45 1.34 0.19 0.20 480395.95 5595361.072 40.95 1.21 0.23 0.24 480396.72 5595363.452 43.45 1.20 0.21 0.22 480397.49 5595365.832 45.95 1.20 0.16 0.19 480398.25 5595368.21

15

2 48.45 1.20 0.17 0.20 480399.02 5595370.592 50.95 1.16 0.14 0.16 480399.79 5595372.972 53.45 1.07 0.14 0.13 480400.55 5595375.352 55.95 0.98 0.08 0.12 480401.32 5595377.732 58.45 0.81 0.10 0.15 480402.08 5595380.112 60.95 0.34 -0.01 0.02 480402.85 5595382.492 63.25 0.00 NA NA 480403.56 5595384.684 1.40 0.00 NA NA 480413.13 5595322.974 3.00 0.33 0.00 NA 480413.58 5595324.514 5.50 0.80 0.08 0.08 480414.28 5595326.914 8.00 0.92 0.10 0.12 480414.98 5595329.314 10.50 0.97 0.11 0.11 480415.68 5595331.704 13.00 1.16 0.11 0.12 480416.38 5595334.104 15.50 1.31 0.08 0.12 480417.09 5595336.504 18.00 1.36 0.10 0.12 480417.79 5595338.904 20.50 1.50 0.13 0.14 480418.49 5595341.304 23.00 1.70 0.13 0.16 480419.19 5595343.704 25.50 1.72 0.14 0.16 480419.89 5595346.104 28.00 1.78 0.11 0.15 480420.60 5595348.504 30.50 1.78 0.12 0.15 480421.30 5595350.904 33.00 1.72 0.16 0.16 480422.00 5595353.304 35.50 1.71 0.16 0.16 480422.70 5595355.704 38.00 1.70 0.11 0.13 480423.40 5595358.104 40.50 1.50 0.12 0.11 480424.11 5595360.504 43.00 1.47 0.14 0.15 480424.81 5595362.904 45.50 1.40 0.11 0.11 480425.51 5595365.304 48.00 1.32 0.09 0.10 480426.21 5595367.704 50.50 1.14 0.06 0.08 480426.91 5595370.104 53.00 0.70 0.04 0.03 480427.62 5595372.494 55.50 0.02 NA NA 480428.32 5595374.894 55.80 0.00 NA NA 480428.40 5595375.185 3.00 0.00 NA NA 480422.90 5595321.975 5.00 0.70 0.07 0.08 480423.33 5595323.925 7.50 0.90 0.11 0.12 480423.87 5595326.365 10.00 0.98 0.12 0.14 480424.41 5595328.815 12.50 1.21 0.10 0.12 480424.95 5595331.255 15.00 1.35 0.11 0.12 480425.49 5595333.695 17.50 1.50 0.11 0.16 480426.03 5595336.135 20.00 1.47 0.13 0.14 480426.57 5595338.575 22.50 1.51 0.12 0.16 480427.11 5595341.015 25.00 1.60 0.12 0.15 480427.65 5595343.455 27.50 1.46 0.12 0.16 480428.19 5595345.895 30.00 1.47 0.14 0.16 480428.73 5595348.335 32.50 1.53 0.14 0.18 480429.27 5595350.775 35.00 1.45 0.17 0.20 480429.81 5595353.225 37.50 1.42 0.17 0.18 480430.35 5595355.66

16

5 40.00 1.56 0.13 0.15 480430.88 5595358.105 42.50 1.52 0.11 0.14 480431.42 5595360.545 45.00 1.28 0.10 0.12 480431.96 5595362.985 47.50 1.11 0.11 0.12 480432.50 5595365.425 50.00 0.80 0.10 0.12 480433.04 5595367.865 52.50 0.05 NA NA 480433.58 5595370.305 52.90 0.00 NA NA 480433.67 5595370.696 0.64 0.00 NA NA 480432.71 5595320.076 3.00 0.60 0.04 0.04 480433.10 5595322.396 5.50 0.97 0.09 0.10 480433.51 5595324.866 8.00 0.96 0.12 0.12 480433.92 5595327.336 10.50 1.02 0.15 0.14 480434.33 5595329.796 13.00 1.06 0.16 0.16 480434.74 5595332.266 15.50 1.25 0.19 0.18 480435.15 5595334.726 18.00 1.35 0.14 0.16 480435.56 5595337.196 20.50 1.51 0.13 0.16 480435.97 5595339.666 23.00 1.44 0.17 0.18 480436.38 5595342.126 25.50 1.45 0.16 0.16 480436.80 5595344.596 28.00 1.54 0.15 0.15 480437.21 5595347.056 30.50 1.25 0.16 0.16 480437.62 5595349.526 33.00 1.24 0.15 0.16 480438.03 5595351.996 35.50 1.38 0.18 0.20 480438.44 5595354.456 38.00 1.33 0.18 0.20 480438.85 5595356.926 40.50 1.25 0.22 0.22 480439.26 5595359.386 43.00 1.06 0.19 0.20 480439.67 5595361.856 45.50 0.78 0.17 0.17 480440.08 5595364.326 48.00 0.66 0.12 0.14 480440.49 5595366.786 50.50 0.05 NA NA 480440.90 5595369.256 50.80 0.00 NA NA 480440.95 5595369.547 1.94 0.00 NA NA 480444.17 5595315.597 4.50 0.71 0.00 0.00 480444.21 5595318.157 7.00 0.72 -0.01 0.01 480444.25 5595320.657 9.50 0.90 0.11 0.12 480444.28 5595323.157 12.00 0.93 0.11 0.12 480444.32 5595325.657 14.50 1.04 0.13 0.12 480444.36 5595328.157 17.00 1.11 0.12 0.13 480444.40 5595330.657 19.50 1.10 0.17 0.16 480444.44 5595333.157 22.00 1.43 0.14 0.18 480444.48 5595335.657 24.50 1.51 0.19 0.20 480444.52 5595338.157 27.00 1.56 0.16 0.19 480444.56 5595340.657 29.50 1.73 0.09 0.13 480444.60 5595343.157 32.00 1.80 0.07 0.13 480444.64 5595345.657 34.50 1.76 0.04 0.14 480444.68 5595348.157 37.00 1.24 0.18 0.18 480444.72 5595350.657 39.50 1.34 0.15 0.16 480444.76 5595353.157 42.00 1.27 0.22 0.23 480444.80 5595355.65

17

7 44.50 1.15 0.20 0.22 480444.84 5595358.157 47.00 0.93 0.17 0.18 480444.88 5595360.657 49.50 0.70 0.17 0.16 480444.92 5595363.157 52.00 0.32 0.09 NA 480444.96 5595365.657 52.55 0.00 NA NA 480444.96 5595366.208 1.86 0.00 NA NA 480452.64 5595317.778 3.86 0.59 0.02 0.02 480452.65 5595319.778 6.36 0.86 0.05 0.09 480452.65 5595322.278 8.86 0.87 0.10 0.12 480452.66 5595324.778 11.36 0.83 0.12 0.13 480452.67 5595327.278 13.86 1.09 0.13 0.15 480452.67 5595329.778 16.36 1.27 0.16 0.18 480452.68 5595332.278 18.86 1.35 0.15 0.20 480452.68 5595334.778 21.36 1.48 0.15 0.20 480452.69 5595337.278 23.86 1.40 0.19 0.20 480452.70 5595339.778 26.36 1.35 0.19 0.18 480452.70 5595342.278 28.86 1.45 0.19 0.19 480452.71 5595344.778 31.36 1.49 0.11 0.15 480452.72 5595347.278 33.86 1.54 0.15 0.16 480452.72 5595349.778 36.36 1.52 0.14 0.19 480452.73 5595352.278 38.86 1.36 0.15 0.21 480452.73 5595354.778 41.36 1.03 0.20 0.22 480452.74 5595357.278 43.86 1.05 0.20 0.20 480452.75 5595359.778 46.36 0.95 0.16 0.15 480452.75 5595362.278 48.86 0.57 -0.01 -0.01 480452.76 5595364.778 51.06 0.00 NA NA 480452.76 5595366.979 1.83 0.00 NA NA 480463.77 5595318.799 3.50 0.49 0.10 NA 480463.69 5595320.459 6.00 0.56 0.11 NA 480463.57 5595322.959 8.50 0.68 0.14 NA 480463.44 5595325.459 11.00 0.81 0.12 0.18 480463.32 5595327.959 13.50 1.04 0.17 0.17 480463.20 5595330.449 16.00 1.27 0.16 0.17 480463.08 5595332.949 18.50 1.29 0.22 0.24 480462.95 5595335.449 21.00 1.29 0.21 0.22 480462.83 5595337.939 23.50 1.16 0.18 0.20 480462.71 5595340.439 26.00 1.09 0.21 0.21 480462.59 5595342.939 28.50 1.12 0.21 0.22 480462.47 5595345.439 31.00 1.14 0.22 0.22 480462.34 5595347.929 33.50 1.51 0.03 0.18 480462.22 5595350.429 36.00 1.51 0.01 0.18 480462.10 5595352.929 38.50 1.53 0.10 0.20 480461.98 5595355.419 41.00 1.53 0.08 0.15 480461.85 5595357.919 43.50 1.60 0.05 0.10 480461.73 5595360.419 46.00 1.20 -0.01 -0.02 480461.61 5595362.909 48.50 0.54 0.05 0.02 480461.49 5595365.40

18

9 50.62 0.00 NA NA 480461.38 5595367.5210 1.60 0.00 NA NA 480471.60 5595320.8510 4.50 0.59 0.05 0.07 480471.59 5595323.7510 7.00 0.71 0.15 0.16 480471.58 5595326.2510 9.50 0.85 0.18 0.14 480471.57 5595328.7510 12.00 1.30 0.13 0.20 480471.56 5595331.2510 14.50 1.38 0.17 0.17 480471.55 5595333.7510 17.00 1.42 0.13 0.18 480471.54 5595336.2510 19.50 1.83 0.05 0.14 480471.53 5595338.7510 22.00 1.86 0.13 0.20 480471.52 5595341.2510 24.50 1.64 0.17 0.14 480471.51 5595343.7510 27.00 1.65 0.18 0.16 480471.51 5595346.2510 29.50 1.60 0.09 0.15 480471.50 5595348.7510 32.00 1.71 0.10 0.16 480471.49 5595351.2510 34.50 1.65 0.17 0.19 480471.48 5595353.7510 37.00 1.54 0.12 0.16 480471.47 5595356.2510 39.50 1.57 0.11 0.12 480471.46 5595358.7510 42.00 1.40 0.03 0.00 480471.45 5595361.2510 44.50 0.94 -0.02 0.00 480471.44 5595363.7510 47.00 0.45 -0.01 NA 480471.43 5595366.2510 48.70 0.00 NA NA 480471.42 5595367.9511 2.00 0.00 NA NA 480481.27 5595321.3411 3.50 0.46 -0.01 NA 480481.22 5595322.8411 6.00 0.95 -0.01 -0.01 480481.13 5595325.3411 8.50 1.04 0.03 0.11 480481.05 5595327.8411 11.00 1.47 0.10 0.12 480480.96 5595330.3411 13.50 1.60 0.11 0.20 480480.88 5595332.8411 16.00 1.96 0.11 0.16 480480.80 5595335.3311 18.50 1.95 0.12 0.18 480480.71 5595337.8311 21.00 2.00 0.16 0.17 480480.63 5595340.3311 23.50 2.02 0.15 0.17 480480.54 5595342.8311 26.00 2.10 0.13 0.15 480480.46 5595345.3311 28.50 2.04 0.13 0.16 480480.38 5595347.8311 31.00 1.97 0.05 0.13 480480.29 5595350.3311 33.50 1.88 0.07 0.18 480480.21 5595352.8211 36.00 1.73 0.13 0.15 480480.12 5595355.3211 38.50 1.67 0.09 0.06 480480.04 5595357.8211 41.00 1.40 0.00 0.00 480479.96 5595360.3211 43.50 1.04 0.02 0.00 480479.87 5595362.8211 46.00 0.71 -0.03 -0.02 480479.79 5595365.3211 48.50 0.16 NA NA 480479.70 5595367.8211 49.20 0.00 NA NA 480479.68 5595368.52

19

Appendix B - Water depths and velocities for each of the ten transects.

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 1

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 2

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 4

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 5

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

Figure 5. The water depth (m) and velocities (ms-1) along transects 1-5 moving from the south to north bank. The depth is indicated by the solid line, the velocity 0.2 m above the gravels (ms-1) by the triangles and the mean column

velocity by the circles (ms-1).

20

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 6

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 7

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 8

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 9

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)



21

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 10

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)

0 10 20 30 40 50 60

2.0

1.0

0.0

0 10 20 30 40 50 60

0.0

0.1

0.2

0.3

Transect 11

Distance (m)

De

pth

(m

)

Ve

loci

ty (m

s1)



22

Appendix C – Photographs

Transect 1 South Transect 1 North

Transect 1 South


23



Transect 5 South

24




25


Transect 9 South


26

Transect 10 South


Transect 11 North

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