APPLICATION OF THE LONGSHORE TRANSPORT CURVE AS AN ENGINEERING TOOL FOR DESIGN OF COASTAL STRUCTURES

Beach nourishment projects can develop localized, high erosion areas known as erosional hotspots. These regions are likely to pose a recurring beach management issue requiring either additional fill in future nourishments or stabilization with structures. In some instances, coastal structures have been viewed with a poor reputation for being overused and misunderstood. It is commonly known that they can result in trapping sand at the expense of the downdrift beach. This is also true of other coastal structures such as breakwaters that slow the transport of sand, and seawalls or revetments that contain it in the uplands. However, when employed in conjunction with beach nourishment and designed with consideration of the longshore transport, the use of coastal structures can effectively address hotspot erosion. By stabilizing the section of beach with accelerated erosion and spreading the erosion over a wider area, the design life of a beach project can be prolonged. The concept of using the shape of the alongshore sediment transport curve to strategically place coastal structures on an eroding section of the beach was originally introduced at ICCE by Campbell and Jenkins (2002). With the increasing costs of placing sand on beaches to keep pace with erosion and climate change, controlling hotspots with coastal structures is becoming a more economically feasible approach. These structures, however, need to be designed with a focus on regional coastal management and rigorous scientific basis.