FIELD STUDY OF A TIDAL INLET, BIMINI, BAHAMAS

Abstract

The inlet bathymetry was mapped by standard photogrammetric techniques after photographing the bottom directly through the water column The channel bottom is bare beachrock or is floored with bioclastic sands and gravels (S G = 2 84) A nine-day time series of observations of current speed and direction, and water temperature and salinity was obtained at two depths at each of eight stations using tripod-mounted, telemetering sensor packages Twelve-to-l8-mmute pulsations in the flow were often observed Spectral analysis of near-surface current speeds shows significant peaks at 2 h, 3 2, k 3, 67, and 12 3 hrs Evolution of sand ripples and dunes was monitored over a 200-ft distance during one tidal cycle The pattern of growth illustrates the differences m bedform geometry which may be expected to influence friction coefficients Evidence is presented for a bottom jet that is induced by flow over the crests of sand waves Tracer sand, sorted into two size groups and color-coded for identification, was released on a flood current Sampling of color-coded tracer sand was conducted by divers using strips of grease-coated plastic tape Spatial distribution of tracers m relation to the bedforms, and the importance to gram erosion of a natural mucoid coating, are noted.