Art (University of Delaware, USA)

Ports and Beaches – Can You Have Both? Perspectives of Ports and Beach Morphodynamics from the US

In the United States over 150 inlets and port systems are maintained annually at a cost of over $1 Billion USD by federal agencies and countless others are maintained by state and local authorities with the goals of maintaining safe navigation and commerce and ameliorating imbalances in the longshore transport of sand caused by the structures that maintain the port/inlet systems.  In this presentation we will examine case studies from around the US and identify common issues encountered in the interaction of port structures and the adjacent coastline and discuss lessons learned and best practices. Our approach will focus on the concept of the littoral cell (or beach compartments) as a framework for understanding the sources and sinks of sediment along the coast. Beach compartments can be conceived of much in the same way as a bank account, if the amount of sediment (sand) being carried out of the system (withdrawn from the account) exceeds the amount coming in then there will be a net deficit that must be compensated for by additional transport or input of sediment or there will be erosion and retreat of the shoreline. Careful consideration must be given to all of the inputs (sources of sediment) and outputs (sinks of sediment) within a system. The location point of ports within the littoral cell can have a tremendous effect on the relative impacts of the development on the adjacent coastline.  Some ports located towards the downdrift end of littoral cells with high longshore transport rates tend to capture large volumes of sediment and require frequent (seasonal or annual) costly dredging or sand bypassing to maintain the harbors and offset nearby beach erosion. Other ports that have been located at the updrift end of littoral cells where transport rates are low may require minimal or no maintenance activities to preserve the function of the harbors and adjacent beaches that may remain stable. With careful consideration and accounting for the sources, sinks, and transport processes the siting and management of port developments can be placed within the context of coastal morphodynamics and thus reduce the conflict between port development and stable beaches.