First year morphological evolution of an artificial berm at Fort Myers Beach, Florida

ERDC/CHL CHETN-II-54 January 2012 Approved for public release; distribution is unlimited. First Year Morphological Evolution of an Artificial Berm at Fort Myers Beach, Florida by Katherine E. Brutsche and Ping Wang PURPOSE: This Coastal and Hydraulics Engineering Technical Note (CHETN) documents the sediment characteristics and first year morphological evolution of an artificial berm placed just offshore in Fort Myers Beach, Florida, based on a series of field data collection periods during the first year after the berm construction. INTRODUCTION: Maintenance dredging is a common practice in inlets and channels for navigation. As a part of regional sediment management, the dredged material is often used for nearby shore protection. One method is placing sand directly on the adjacent beach. The other is placement of a nearshore berm, i.e., to add sediment to the littoral system and/or act as a breakwater to dissipate wave energy and slow erosion (Allison and Pollock, 1993). Compared to beach fill, berm nourishment may have the advantage of being less costly with more lenient restrictions on the dredged material. Artificial nearshore berms can be categorized depending on their dynamics or intended purpose. Hands and Allison (1991) defined two types of berms based on mobility. Stable berms are those that remain at the placement site and retain most of their volume over several years. Active berms show movement and changes within a few months. Hands and Allison (1991) and Hallermeier (1981) suggested that wave climate and closure depth are good indicators of whether a berm would be active or stable. Aidala et al. (1996) and Work and Otay (1996) indicated that bottom shear stress and horizontal bed velocities are also good indicators of berm stability. McLellan and Kraus (1991) describe design guidance for two different types of berm: a feeder berm and a stable berm. A Feeder berm is placed in such a way that under accretionary wave action, sediment will be added to the