Simplified Dean's Method for Beach-Fill Design

Abstract

A simplified approach is presented to use Dean's method for determining dry-beach (subaerial) width after equilibrium for arbitrary sediment size. A simple equation is developed relating a key parameter in Dean's method to sediment diameter. Closure depth is shown to be simply related to nearshore mean annual significant wave height. Dean's equations for dry-beach width are dimensionalized and simplified. The key parameter, closure depth, and the equations for dry-beach width are all presented in simple forms that can be solved easily using a hand calculator. Examples are presented for all cases including fill sediment with a mean diameter the same size, larger, and smaller than the native sediment. When the fill sediment is finer than the native sediment a minimum quality of sediment has to be placed before there is any resulting dry beach, and an equation is provided to determine this minimum quantity. The simplified method presented allows an engineer to easily evaluate a large number of scenarios at the feasibility stage of a project.