Title
North Delta Sedimentation Study
Author Information
Kavida Subbaroyan
American River College,
Geog350: Data Acquisition in GIS;
Spring 2006
Abstract
The study investigates the Flow Measurement and Bed sample in the Delta using Acoustic doppler channel profiler,GPS and computer modeling technigues. The Objective of the study is to develop an appropriate tool for modeling sedimentation transport and channel morphology within the study area. The results of the study will be used to know about the flow into and out of a junction.
Introduction
The distribution and transportion of sediments in the Sacramento-San Joaquin Delta impacts many activities in the region including navigation, recreation, fisheries development and flood control.The physical processes that initiate and control sediment transport in the Delta are sensitive to the hydrology and hydraulics of the system, and small changes in these variables have been found to initiate substantial responses sometimes with unforeseen results. Sendimentation analyses are, therefore an essential part of any proposal that may effect local waterways.
Background
The study area for which assessment was conducted is shown in Figure(a). Calculations were performed for selected representative cross sections of the streams comprising the study area including the Mokelumne River,Dead Horse Cut, Snodgrass Slough and Last Slough. The cross Sections at which sediment transport was calculated were selected on straight river reaches in the vicinty of the main stream junctions. A few additional cross sections were selected on the streams upstream and downstream of the study area to estimate sediment transport variablility along the stream.
Methods
Discharge measurements were taken at ten locations within the North Delta study area. Flowrates in each channel reach were measured using an acoustic doppler channel profiler (ADCP) attached to the bow of a small boat. Most measurements of flow into a junction were taken within a few minutes of each other. so that tidal effects were minimized. The locations of the flow sampling sites are also presented in Figure(b). The results of the discharge measurements at the four junctions are presented in Table 1a through 1d. The column diffQ in the tables represents the net sum of flow into and out of a junction. A positive value in this column implies water stroge at a junction and increasing water levels, whereas a negative value implies decreasing water storage and surface levels.
Results
Table 1a. Measured discharges near the Delta Cross Channel Junction
|
Date
|
Sampling Time
|
Reach 1
|
Reach 2
|
Reach 5
|
diff Q (cfs)
|
|
02/27/06
|
11:13 - 11:36
|
9495
|
m
|
-3884
|
-
|
|
02/28/06
|
11:06 - 11:24
|
8388
|
-1404
|
-7330
|
-346
|
|
02/28/06
|
13:02 - 13:28
|
10743
|
-8846
|
-3063
|
-1166
|
|
02/28/06
|
15:17 - 15:55
|
13516
|
-11517
|
-2164
|
-165
|
Table 1b. Measured discharges at Snodgrass Slough Junction
|
Date
|
Sampling Time
|
Reach 5
|
Reach 6
|
Reach 7
|
diff Q (cfs)
|
|
02/27/06
|
12:09 - 12:48
|
1205
|
2194
|
-2985
|
414
|
|
02/28/06
|
11:06 - 11:57
|
7330
|
-2627
|
-4568
|
135
|
|
02/28/06
|
12:24 - 13:07
|
3063
|
-833
|
-3272
|
-1042
|
|
02/28/06
|
15:12 - 15:37
|
2164
|
2081
|
-4312
|
-66
|
Table 1c. Measured discharges near the Dead Hourse Island
|
Date
|
Sampling Time
|
Reach 7
|
Reach 8
|
Reach 9
|
diff Q (cfs)
|
|
02/27/06
|
10:08 - 10:40
|
3311
|
-2261
|
-1171
|
-121
|
|
02/28/06
|
10:29 - 10:48
|
4568
|
-2929
|
-1579
|
60
|
|
02/28/06
|
12:04 - 12:29
|
3272
|
-2515
|
-1212
|
-455
|
|
02/28/06
|
14:52 - 15:15
|
4312
|
-3401
|
-962
|
-51
|
Table 1d. Measured discharges at near New Hope Landing
|
Date
|
Sampling Time
|
Reach 9
|
Reach 10
|
Reach 11
|
Reach 12
|
diff Q (cfs)
|
|
02/27/06
|
9:31 - 10:12
|
1171
|
-2078
|
-510
|
214
|
-203
|
|
02/28/06
|
10:01 - 10:31
|
1579
|
-985
|
-1042
|
301
|
-146
|
|
02/28/06
|
11:38 - 12:07
|
1212
|
-641
|
-679
|
-35
|
-143
|
|
02/28/06
|
14:29 - 14:54
|
962
|
935
|
-1266
|
-553
|
78
|
Figures and maps
Figure (a). The Sacramento- San Joaquin Delta and extent of the project area.
Figure (b). Location of bed material and flow discharge sampling sites in project area.
Analysis
ADCP is used across the water flow to measure the velocity and depth. We get velocity(V) from the machine and the depth of the channel is the distance driven by the boat (d).
Hence cfs ( Cubic flow per Second ) can be calculated by multiplying velocity and the depth.
cfs= v*d
The sum of flow rate is calculated to know how well the measurement is.
The value we obtained was between -1166 to 414 which is almost equal to zero.
Conclusion
We know according to math difference between flowin and flowout should be zero, but in the table of data we got is not equal to zero. This result in not accurate because of two reasons. the first is the error in the measurement we took and the second is the flow is always changing over time,not able to calculate the flow in that speed.
References
Ackers,P. (1993). Sediment transport in Open Chennels: Ackers and White Update. Proc. Instn Civ. Engrs Wat., Marit. & Energy, 101, pp 247-249
Atwater,B.F., 1982. " Gelogic maps of the Sacramento- San Joaquin Delta, California", U.S. Geological Survey.
Learn HTML: http://www.w3schools.com/html/default.asp
Rojstaczer.S.A., Hamon, R.E., Deverel,S.J., Massey,C.A., 1991, "Evaluation of selected data to assess the causes of subsidence in the sacramento -San Joaquin Delta, California"U.S. Geological Survey Open-File Report.
USGS,2000. 'Water database, available via the Internet at http://water.usgs.gov
