Beach Nourishment: Benefits, Theory and Case Examples

Abstract

Beaches provide a wide range of societal benefits including storm protection, recreation, and habitat for a number of species. However, many beaches are under natural and/or human induced erosional pressures. The engineer is left with few choices to address this erosional pressure: (1) Correct the erosional cause which is usually practical only if the cause is human related, (2) Retreat from the shoreline, (3) Armor the shoreline, and (4) Beach nourishment which comprises the placement of large quantities of good quality sand in the nearshore system. In many cases, beach nourishment is the only practical environmentally friendly approach of those identified. Emphasis is directed to the benefits of beach nourishment and methodology which identifies the critical design factors. The application of a simple numerical model to predict the performance of two case examples is illustrated. 1. Beaches, Beach Erosion and Available Engineering Options Beaches provide many benefits to society and the natural system. These benefits include storm protection to upland structures, recreational opportunities especially in urban settings and habitat for a number of species. Many of the World's shorelines are eroding at varying rates due to both natural and/or anthropogenic causes. Due to the attractiveness of shorelines for commercial and residential sites, erosion is of increasing concern and methods are often sought to address this issue. There are surprisingly few options to deal with an eroding shoreline: (1) Correct the cause of the erosion, (2) Retreat from the shoreline, (3) Employ structures, and (4) Beach nourishment. The ideal option would be to correct the cause of erosion; however, this is usually only possible in limited cases in which the cause is due to anthropogenic activities, such as harbor development that interrupts the net longshore sediment transport, trapping of sand in constructed upland reservoirs, sand mining, inducement of ground subsidence through withdrawal of hydrocarbons or other ground fluids, etc. In the case of interruption of longshore sediment transport, correcting the cause requires reinstatement of the net longshore sediment transport. Retreat from the shoreline is only practical on shorelines that are relatively undeveloped and this option is increasingly less attractive with the trend of coastal development. Examples of the structural option include construction of groins and/or coastal armoring such as seawalls or revetments, each of which has some adverse effects. Groins trap sand from the littoral system, thus stabilizing the beach; however, in 25 C. Zimmermann et al. (eds.), Environmentally Friendly Coastal Protection, 25-40.