PROFILE VOLUMES AS A MEASURE OF EROSION VULNERABILITY

Abstract

Profile volumes provide an indication of the condition of barrier islands and beaches. While site specific, they can be used along any littoral shoreline as a measure of the relative "health" of one section compared with another. Assuming shorelines develop an equilibrium profile around which the beach cycle and cross shore changes occur, profile volumes integrate small scale perturbations and provide a target sediment volume for the site between reference contours. Profile volumes may be considered for various parts of the profile as follows: - Dune volume above storm surge levels (after FEMA) as a measure of the reservoir of sand required to prevent over topping. - Mean sea level (MSL) barrier cross-section - the section that must be fully scoured to produce a full breach channel. - Inner beach profile - the section that represents the condition of the recreational beach. - Inshore profile - the section that represents the core "base" of the barrier island. By comparing versions of these sections from site to site, especially where there have been known breaches and variations in beach erosion rates it is possible to develop systematic criteria for the health of the shoreline in question. Profile volumes provide a straight-forward technique for diagnosing barrier erosion problems. A case study from Westhampton Beach and Fire Island (New York) illustrate the application.