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Field Measurements of Local Pier Scour in a Tidal Inlet.

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Master's thesis,

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Present design criteria and existing scour prediction models were developed primarily from the study of steady, homogenous, unidirectional flow. These models have been extensively reviewed and fine tuned, and for the riverine environment provide a good basis for the design effort. However, tidal flows are not normally unidirectional. A multitude of hydrodynamic processes affect these inlets and cause the current to alternate and change directions. Wind, waves, storm surge, runoff seich, and river discharge can affect the direction and velocity of the current, but the primary source of the alternating current is the astronomical tides. This paper will examine local pier scour, and in particular look at scour that occurs under the unsteady, reversing flow condition at a tidal inlet. There is very little known about this cyclic scour process. Most of the local scour studies have been conducted in laboratory flumes under steady flow conditions. Due to the lack of complete field data i.e. experiments where all pertinent parameters are measured it is impossible at this time to accurately relate laboratory results to prototype situations. This is true for steady flow as well as the more complex unsteady flow situations. In the meantime bridges and other structures must be designed using the best available information. Accurate, well documented field measurements thus provide much insight into the complex fluid dynamics and sediment transport processes that are involved in local sediment scour. The primary focus of this report will be to develop the techniques and equipment needed to monitor and capture the scour processes on a prototype scale structure. Exactly what data is needed and how we capture this data in the actual field environment will be examined. MM

Subject Categories:

  • Physical and Dynamic Oceanography
  • Civil Engineering

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