Response and Recovery to Sediment Influx in the Rappahannock Estuary: A Summary

Flooding from Tropical Stonn Agnes produced unique hydrographic conditions for transport and dispersal of sediment in the Rappahannock and .James estuaries. Analyses indicate two cycles of response and recovery to the shock of extreme freshwater and sediment influx; one cycle in response to Rappahannock inflow; the other to intense mixing within the estuary. Important stages in the sequence consist of: (1) an initial response and seaward surge of river water and sediment; (2) shock with downstream translation of the salt intrusion head with a near-bottom salinity front and high turbidity in surface and in bottom water; (3) rebound with intense stratification and formation of an enriched turbidity maximum; (4) partial recovery with salinity intrusion strengthened by upstream flow along the bottom; landward migration of the maximum; (5) full recovery and return to partly-mixed state with decay of turbidity maximum over a broad zone 30 days after flooding. Sediment was derived initially from lateral tributaries and then from the main river. The bulk of the load sedimented above the salt intrusion during the first three days of flooding. Sediment dispersed into the estuarine circulation system later was effectively trapped by upstream flow along the bottom. Over the entire event, 91% of the sediment load was trapped.https://scholarworks.wm.edu/vimsbooks/1066/thumbnail.jp