Channel Processes and form Near the Tidal Limit
Coastal plain river flow is driven by the topographic gradient unless acted on by marine tides. Where sufficiently strong tides occur, a tidal wave will enter the river mouth and advance upstream until it dissipates due to bottom friction and downstream flow. It follows that near the upstream extent of tidal influence along a river channel, freshwater currents transition from fully unidirectional to fully bi-directional. The goal of this study is to investigate channel conditions near the upstream tidal limit of the Santee River, SC. I measured velocity profiles, bathymetry, channel geometry, and collected sediment grab samples at this transition zone. Field observations and analyses suggest there are three characteristic channel reaches in the downstream direction: the first is an alluvial, sinuous, convergent drainage network, the second is straight and bedrock floored, and the third is an alluvial, sinuous, divergent drainage network with each reach composed of medium to coarse sands. The most notable bathymetric features are three deep spots that occur at bends in the channel. Estimated shear stress values within my study site show that tidal flow during ebb or flood tide is too weak to induce erosion. This indicates my study site is a river dominated environment with the deeps likely formed as a result of enhanced secondary currents during a rise in stage and discharge when tidal affects are dampened.
Earth Sciences, Geology, Physical Sciences and Mathematics, coastal plain river, geomorphology, tidal limit
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