A Tracer Study of Sediment Transport in the Vicinity of a Groin: New York, U.S.A.

Abstract

A field experiment was conducted at Riis Park, New York in October, 1986, to measure sediment transport paths past the end of a semi-permeable, rubble groin. Fluorescent-tagged sands were used to identify patterns of transport. Flow characteristics of waves and currents were measured with current meters. Tube cores were taken to sample sediment and recover tracer sands. Sampling runs were conducted at approximately half-hour intervals for two hours, and a final run was made approximately 24 hours after injection. The results indicate that a primary path of sediment transport is past the end of the groin and then immediately shoreward. After the 24-hour interval, approximately 30% of the deployment volume was represented in samples onshore and downdrift of the injection point. The findings suggest that this groin does not contribute to downdrift erosion under the measured circumstances, but short-term, prototype studies such as these may not be representative of typical conditions in a nearshore system.