Alrushaid, Tariq I S I (2018-05). Wind-Driven Nearshore Dynamics in the Gulf of Mexico. Doctoral Dissertation. Thesis uri icon

abstract

  • Coastlines around the Gulf of Mexico are dynamic, due to prevailing energetic wind systems such as frequent cold fronts and diurnal wind systems. In the last two decades, more research has focused on the surf zone's complex coupling effects between winddriven waves and currents. However, there is still a need for further field based experiment to elucidate, (1) how offshore cold fronts impact nearshore morphodynamics and sediment dynamics, when compared to onshore fronts, (2) what is the main physical forcing that controls the surf zone and the inner-shelf region current circulation during relatively intense onshore and offshore wind events, and (3) does the cumulative effect of sea breeze cycles result in more morphodynamic variation than cold fronts? Therefore, two field based studies were conducted in the Gulf of Mexico to advance our understanding of the complex coupling effects between wind-driven waves and currents, including turbulence quantities, sediment transport parameters, and morphodynamic processes. Both field experiments included time-series of highly resolved hydrodynamics and suspended sediment concentration obtained at different cross-shore locations across the surf zone. The first field experiment was conducted at a sea breeze dominated beach on Sisal, Yucat?n Peninsula, M?xico. Time-series observations suggest that the impact of sea breeze cycles on the nearshore hydrodynamics and morphodynamics is comparable to the effect of onshore-directed cold front, and cumulatively the sea breeze cycles will result in higher sediment loss. Regardless, it is also suggested that the cumulative accretional of the land breeze cycles can be sufficient to compensate for the loss of sediment by either the sea breeze cycles or the cold fronts. The second field experiment evaluated surf zone hydrodynamics and sediment dynamic processes within the upper Texas coast during three offshore cold front events and three onshore Gulf breeze events. Observations show enhanced eastward suspended sediment transport following the passage of cold fronts, while westward transport was experienced during the Gulf breeze events. The study suggests that during late fall and early spring seasons, Galveston Island will experience higher erosion rates in the eastside, while accretion of sediment on the west side will occur.
  • Coastlines around the Gulf of Mexico are dynamic, due to prevailing energetic wind systems such as frequent cold fronts and diurnal wind systems. In the last two decades, more research has focused on the surf zone's complex coupling effects between winddriven waves and currents. However, there is still a need for further field based experiment to elucidate, (1) how offshore cold fronts impact nearshore morphodynamics and sediment dynamics, when compared to onshore fronts, (2) what is the main physical forcing that controls the surf zone and the inner-shelf region current circulation during relatively intense onshore and offshore wind events, and (3) does the cumulative effect of sea breeze cycles result in more morphodynamic variation than cold fronts? Therefore, two field based studies were conducted in the Gulf of Mexico to advance our understanding of the complex coupling effects between wind-driven waves and currents, including turbulence quantities, sediment transport parameters, and morphodynamic processes. Both field experiments included time-series of highly resolved hydrodynamics and suspended sediment concentration obtained at different cross-shore locations across the surf zone.

    The first field experiment was conducted at a sea breeze dominated beach on Sisal, Yucat?n Peninsula, M?xico. Time-series observations suggest that the impact of sea breeze cycles on the nearshore hydrodynamics and morphodynamics is comparable to the effect of onshore-directed cold front, and cumulatively the sea breeze cycles will result in higher sediment loss. Regardless, it is also suggested that the cumulative accretional of the land breeze cycles can be sufficient to compensate for the loss of sediment by either the sea breeze cycles or the cold fronts. The second field experiment evaluated surf zone hydrodynamics and sediment dynamic processes within the upper Texas coast during three offshore cold front events and three onshore Gulf breeze events. Observations show enhanced eastward suspended sediment transport following the passage of cold fronts, while westward transport was experienced during the Gulf breeze events. The study suggests that during late fall and early spring seasons, Galveston Island will experience higher erosion rates in the eastside, while accretion of sediment on the west side will occur.

publication date

  • May 2018