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Historical Bathymetric Change in Suisun Bay 1867 - 1990
United States Geological Survey
Cappiella, K., Malzone, C., Smith, R. E., and Jaffe, B. E.
Sedimentation and Bathymetry Changes in Suisun Bay: 1867-1990

1867-1887

1887-1922

1922-1942

1942-1990

1867-1990

Erosion* -42 -112 -92 -128 -219
Deposition* 103 64 43 68 120
Net Volume Change* 61 -48 -50 -61 -99
Change Rate** 3 -1 -2 -1 -1
Sedimentation Rate*** 3.0 -1.4 -2.4 -1.2 -0.7
% erosional area 30 63 55 60 63
% depositional area 58 32 35 33 34
*million cubic meters     **million cubic meters/year     *** cm/square meters/year

Charts of erosion and deposition (18 KB), sedimentation (22 KB), and sedimentation rates (17 KB) were created using the above data. Tidal flat change is another important aspect of this project because the area of tidal flat in the Bay fluctuated in response to changes in sediment delivery. Using the 1867 and 1990 bathymetric grids, it was determined that the area of tidal flat in Suisun Bay decreased from 41 square km in 1867 to just over 12 square kilometers in 1990. The area of tidal flat peaked in 1887 at 52 square kilometers, presumably because of the large influx of hydraulic mining debris. After 1887, when water projects caused decreased sediment supply to the Bay, and much of the tidal flat/marsh area was diked, the area of tidal flat decreased significantly. A graph of tidal flat change (15 KB) in Suisun Bay was created from the above data. Island changes also occured in Suisun Bay over the study period. The area of island coverage in the bay decreased gradually from 24.42 square kilometers in 1867 to 18.70 square kilometers in 1990. The time period with the fastest rate of change was 1942-1990, during which much of the surface area of Sherman Island was lost due to flooding of the island because of levee failure.

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