ERDC Coastal and Hydraulics Laboratory Coastal and Hydraulics Laboratoryicksburg
The harbor structuresshoreline armoring on the southern Lake Michigan shoreline interrupt sand migration. Ogden Dunes, Indiana, and the nearby Indiana Dunes National Lakeshore observed shoreline erosion due to engineered structures associated with Burns Waterway Harbor east of Ogden Dunes impeding natural east-to-west sediment migration. To remedy this, USACE placed over 450,000 cubic meters m3 of dredged material post-2006 in the nearshore of Ogden Dunes. However, the effectiveness of nearshore placements for shoreline protection and littoral nourishment is not fully established. To improve nearshore placement effectiveness, USACE monitored the JuneJuly 2016 placement and subsequent movement of 107,000 m3 of dredged material in the nearshore region at Ogden Dunes. This involved an extensive monitoring scheme three bathymetry surveys, and two acoustic Doppler current profiler deployments, a Coastal Modeling System CMS numerical model of the changes following placement, and a prediction of sediment transport direction using the Sediment Mobility Tool SMT. The SMT-predicted sediment migration direction was compared to observations. Observations indicated that between 10112016 and 11152016 the centroid of the sediment above the pre-placement survey moved 17 m onshore. These observations agreed with SMT predictions onshore migration under storm and typical wave conditions. CMS accurately reproduced the hydrodynamic features.