Statistical Description of Longshore Transport Environment

Abstract

The longshore transport environment at a coastal site is represented in terms of six parameters. The total population of longshore transport‐rate observations at a site is separated into two populations, positive transport and negative transport, each of which can be described by a log‐normal probability distribution. The six parameters describing the environment are the two means and standard deviations that define the two log‐normal distributions and the fractions of time the transport is positive and negative. The log‐normal distribution appears to fit data from a wide variety of sites and for a wide range of types of wave data. Longshore transport rates calculated from longshore current observations depend on surf‐zone width; thus the coefficient relating longshore transport rates to surf‐zone conditions varies from site to site. Annual net longshore transport rates are normally distributed. Synthetic net transport‐rate data at Indian River Inlet, Delaware, was generated having the same statistical parameters as the observed transport rates.