Doctor of Philosophy (PhD)
Oceanography and Coastal Sciences
This dissertation investigates the hydro-morphodynamics of two major components of a sandy coastal environment: tidal inlets and embayment shorelines. In the first study, I focused on the evolution of inlet geometry by compiling and analyzing a database with 226 inlets worldwide with a special attention given to their width to depth ratio (or aspect ratio). I found that the aspect ratio has a weak dependency on tidal range and wave height, and they lie in different ranges for three types of tidal inlets: engineered, natural single-thread, and natural compound. I also developed a 2D hydro-morphodynamic model of an idealized barrier-inlet system to conduct sensitivity analysis for two specific parameters that represent bank erosion processes: the transverse bed gradient factor (αbn) and the dry cell erosion factor (θsd). I found that αbn = 5 – 10 and θsd = 0.3 – 1.0 provides inlet configurations for natural inlets that best conform to observations. In the second study, I explored wave and tidal characteristics of Hamelin Pool, a shallow carbonate embayment in Western Australia, by applying a 2-D hydrodynamic model. The area features living stromatolites near the embayment shorelines, and I focused the attention to a certain type of elongated stromatolites (i.e., seif stromatolites). I concluded that their orientation is likely affected by wave processes rather than tide or wind induced currents. In the third study, I aimed to detect microbial growth on sandy carbonate bed sediments. For this purpose, I analyzed wave and near-bed turbidity data recorded at a subtidal location in Hamelin Pool from July 2017 to March 2018. Laboratory experiments were also performed to separate the contribution of mud and sand to the total water turbidity, which resulted in a novel conclusion that the standard deviation of turbidity – as opposed to the mean value – can be used as a proxy for sand resuspension. Analysis of the turbidity time series revealed a seasonal reduction of erodibility, which was hypothesized to be caused by microbial growth, i.e., by biostabilization.
Murshid, Shamim, "Hydro-Morphodynamics of Sandy Coastal Embayments" (2021). LSU Doctoral Dissertations. 5516.
Available for download on Tuesday, March 15, 2022