Equilibrium of Crenulated Bays in Thailand

Abstract

The C coefficients in the now well-known parabolic bay shape equation (PBSE) are the most important parameters for verifying the bay beach stability or designing a headland bay beach in static equilibrium. These coefficients are revised specifically for bays in static and dynamic conditions in Thailand. Three techniques, namely Least Square (LS), Genetic Algorithms (GA), and Differential Evolution (DE) are used to determine the alternative coefficients. The newly derived C coefficients for static equilibrium bays (SEB) differ slightly from the original coefficients. Dynamic equilibrium bays (DEBs) with sediment within the embayment are analyzed to obtain a new set of C coefficients, which are a function not only of wave obliquity but also sediment supply ratio (SSR), which is a new parameter representing the ratio between the rate of sediment supplied from a river source to the bay and the longshore sediment transport rate. The resulting new C coefficients for DEBs vary uniformly and systematically, similar to those for the SEBs, and are expected to be applicable to DEBs elsewhere for coastal management.