Sudden Clearing of Estuarine Waters upon Crossing the Threshold from Transport to Supply Regulation of Sediment Transport as an Erodible Sediment Pool is Depleted: San Francisco Bay, 1999 |
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Authors: | David H Schoellhamer |
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Institution: | (1) US Geological Survey, 6000 J Street, Placer Hall, Sacramento, CA 95819, USA |
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Abstract: | The quantity of suspended sediment in an estuary is regulated either by transport, where energy or time needed to suspend
sediment is limiting, or by supply, where the quantity of erodible sediment is limiting. This paper presents a hypothesis
that suspended-sediment concentration (SSC) in estuaries can suddenly decrease when the threshold from transport to supply
regulation is crossed as an erodible sediment pool is depleted. This study was motivated by a statistically significant 36%
step decrease in SSC in San Francisco Bay from water years 1991–1998 to 1999–2007. A quantitative conceptual model of an estuary
with an erodible sediment pool and transport or supply regulation of sediment transport is developed. Model results confirm
that, if the regulation threshold was crossed in 1999, SSC would decrease rapidly after water year 1999 as observed. Estuaries
with a similar history of a depositional sediment pulse followed by erosion may experience sudden clearing. |
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