Influences of False Bay Creek and Waves on Sediment

Abstract

The primary objective of this study was to increase the understanding of the influence of False Bay Creek and wave processes on grain size distribution and sediment organic carbon in a shallow, enclosed bay. Two parallel transects were sampled to compare grain size distribution change over distance from the shoreline near False Bay Creek (Transect 1) and 250 m from the creek mouth (Transect 2). The distributary channel created by False Bay Creek also was sampled to compare grain size distribution and organic carbon to Transect 1 and Transect 2. Grain size analysis was quantified by sieving and organic carbon was quantified through loss on ignition. False Bay Creek forms a small delta that is composed of poorly sorted, sandy gravel and has an edge visible in satellite imagery. Past the delta, the sediment is better sorted, and the amount of fine sand increased. As distance from the shoreline increased, the amount of medium sand increased. Along Transect 2, the amount of fine and very fine sediment decreased, and medium sand increased as distance from the shoreline increased. Due to the bathymetry, roughly circular shape, and narrow mouth of False Bay, wave refraction and diffraction likely results in the transport of fine and very fine sediment to the head of the bay and wave action increases sorting of sediment as distance from the shoreline increases.