Capacity of inlet outer bars to store sand.

Abstract

Inlets act as large sand sinks for sand derived from adjacent beaches. An attempt to quantify the amount of sand in an outer bar is made with the major governing parameter of inlet hydraulics, tidal prism. In areas of high wave activity there appears to be a well defined limiting relationship to the amount of sand stored in the offshore bar as a function of tidal prism. In areas where inlets are exposed to lower wave activity, more scatter is noted in this correlation. Relationships for estimating the equilibrium storage volume of sand in the outer bar/shoal of newly cut inlets in highly exposed, moderately exposed, and mildly exposed coasts (where degree of exposure relates to wave action offshore) are proposed for use in estimating quantities of sand which will eventually be lost to adjacent beaches. A conclusion of the study is that more sand is stored in the outer bar of a low energy coast than in the outer bar of a high energy coast. An upper limit to outer bar storage in low energy zones may be a function of additional parameters other than tidal prism such as longshore energy flux at the inlet site and inlet history. (A)