Deposition in upper Patuxent estuary, Maryland, 1968–1969

Abstract

Urbanization leads to increased runoff and sediment discharge during construction as shown in a year-long study of the Patuxent River drainage basin during a period of intense development for housing. Although precipitation was only 80% of previous years, water discharge to the estuary was 2.4 times the average. A net upstream flux of suspended sediment indicated that all fluvial suspended sediment was deposited in the upper reaches of the estuary. Two areas of net deposition were separated by a central turbidity maximum, which fluctuated in position over a 10-km distance in response to high or “average” river discharge. During low river discharge, two turbidity maxima were observed; one, corresponding with the salt front; and the other, with a downstream constriction in the estuary channel. The average rate of deposition in the upper 50 km of the estuary was calculated to be 7.45 g cm −2 year −1. If approximately 20% of the riverborne sediment was deposited between the tidal limit and the average position of the salt front, then 5.88 g/cm 2 were deposited during the study period, forming a layer with an average thickness of 3.7 cm.