Sediment transport and budget influenced by harbor jetties in storm events

Document Type

Article

Publication Date

12-24-2024

Department

Great Lakes Research Center; Department of Civil, Environmental, and Geospatial Engineering

Abstract

Accelerated coastal erosion in Lake Michigan has been reported throughout the basin and on regional scales. A significant portion of regional coastal erosion is influenced by coastal structures such as harbor jetties of varying sizes. To understand the effects of coastal structures on local sediment transport and budget, this study focuses on medium-sized harbor jetties at South Haven, MI, in southeastern Lake Michigan, representative of many recreational harbors and harbors of refuge along Great Lakes shorelines. The wave-current-sediment transport processes were simulated using a coupled model, which integrates Simulating Waves Nearshore (SWAN), Finite-Volume Community Ocean Model (FVCOM), and Community Sediment Transport Modeling System (CSTMS). Our results indicate that during storm events, the presence of a pair of jetties consistently leads to a substantial decrease in longshore sediment transport on the downdrift side within a 2 km region. For the entire navigation season from April to December, the storm-time averaged currents and longshore sediment transport are predominantly southward. The jetties increase net sediment transport updrift of the jetties and enhance offshore sediment transport. Simultaneously, they significantly reduce downdrift sediment transport, with persistent eddy structures near the jetty limiting the sediment transported out of the immediate region adjacent to the southern jetty. Consequently, sediment can accrete on both sides of the jetties, potentially widening the beaches. Meanwhile, the region further south of the jetties experiences severe erosion due to a reduced sediment supply from upstream. Understanding the dynamics of sediment transport and budget, particularly with the jetties’ influences, is crucial for coastal management.

Publication Title

Journal of Great Lakes Research

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