Turbidity associated with the beneficial placement of dredged sediment in the dynamic littoral zone at Fairport Harbor, Ohio

Abstract

The nearshore placement of sediments dredged via maintenance of navigation channels is a cost-effective management solution which offers myriad benefits that can include shoreline protection and habitat restoration. Benefits can be offset by concerns due to potential effects on the ecosystem from turbidity generated during placement. This study investigates the turbidity and geomorphic response of dredged sediment placed within the dynamic littoral zone of Lake Erie. Turbidity was measured at nine locations before, during, and after nearshore dredged material placement, and bathymetry was measured in four surveys to capture the effects of placing 39,400 m³ of material from Fairport Harbor, Ohio. Nearshore turbidity measurements collected before dredging occurred could be explained using wave data, which provided an estimate for expected background turbidity during and after dredging. These wave models continued to fit measured turbidity data well during and after dredged material placement and indicate sediment placement did not significantly increase turbidity at any of the monitoring locations. Bathymetry surveys indicate sediment was placed within the active littoral zone and may have contributed to accretion along the onshore edge of the pre-existing bar. These observations indicate that nearshore placement of dredged material in this environment is aligned with natural sediment movement in the littoral zone, with minimal to negligible generation of turbidity beyond what occurs naturally.