Identifier

etd-04172009-123540

Degree

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Document Type

Dissertation

Abstract

The primary objective of the study is to develop an effective tool to investigate the resuspension, deposition and transport of mixed cohesive and non-cohesive sediments in an estuary. The research has integrated 1) statistical analyses of the primary forcing, 2) numerical models for hydrodynamics, surface waves and sediment transport, and 3) the MODIS (Moderate Imaging Spectroradiometer) remotely sensed imagery, to investigate hydrodynamics and sediment dynamics in Mobile Bay, Alabama. First, based on long-term meteorological and tidal observations, statistical analyses have been conducted to predict extreme values of winds and water levels at different return periods in the estuary. Application of predicted extreme winds and surges is illustrated though the development of a storm wave atlas and through the estimation of erosion potential in the estuary. Secondly, three open-source community models for estuarine circulation, wind wave prediction, and sediment transport have been coupled and carefully tested against available field measurements. In particular, the sediment transport model has been improved by implementing the continuous deposition scheme, the general solution to the wave-current bottom boundary layer model (Grand and Madsen, 1979), and a formula of flocculation-influenced settling velocity (Whitehouse et al., 2000). Idealized test cases were designed to evaluate the performances of the integrated model system, in addition to model calibration and verification using field observations. Thirdly, a new algorithm has been developed based on the suspended sediment concentration measured from field water sampling and the corrected MODIS red-channel reflectance for Mobile Bay. The algorithm has been applied not only to winter-front and post-hurricane conditions to reveal the impact of different forcing agents on sediment dynamics in Mobile Bay, but also to the normal weather condition for providing guidance to calibrate the sediment transport model. Integration of these three different approaches has enabled us to understand how land-based particulates are transported, deposited and re-suspended in the estuary, and to disclose the dynamic changes of the suspended sediment concentration under normal and extreme forcing. The methodology and tools developed in this study can be used for other coastal areas.

Date

2009

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Qin Chen

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