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An Investigation of Stochastic and Process-Based Models Describing the Influence of Vegetation and Storms on Barrier Island Dynamics
Abstract
Barrier islands are dynamic coastal landscapes that protect beach communities and low-energy environments from storms. This role of a barrier system is mainly controlled by its elevation, the result of delicate coupling between accretional and erosional processes. This Dissertation investigates, through stochastic and process-based models, the influence of vegetation and water-driven erosion on barrier dynamics, mainly through the evolution of coastal dunes.
Chapter 1 focuses on the validation of a reference stochastic model for point evolution of barrier elevation using field data. In this regard, the model is extended alongshore by associating the randomness of the processes involved with barrier morphology. Parameter extraction methods are here developed to validate the steady-state predictions. The key controller of the barrier state is identified as the base elevation an island is left with after an overwash. To study the effect of vegetation dynamics that is relaxed in the stochastic model a process-based model is introduced in Chapter 2. First, an equivalence is established between the two models by incorporating the stochastic nature of water-driven erosion into the process-based model. Then in Chapter 3, the dune dynamics involving the competition between water-driven erosion and dune growth under different vegetation conditions are analyzed by modifying its associated parameters, mainly vegetation growth time and colonization time (function of the initial cover fraction). Vegetation causes an initial lag in dune formation due to the colonization time and in turn, controls the recovery under flooding. Based on these dynamics, the dune growth can be divided into two regimes, stable and mobile. Within the stable regime, the influence of vegetation on dune recovery is quantified by the colonization time and helps in the identification of suitable parameters to describe the barrier island state. Finally, a vulnerability indicator is obtained in terms of a critical base elevation after an overwash. This indicator connects all the relevant processes here investigated: vegetation colonization, dune development, and flooding frequency.
Citation
Ramakrishnan, Kiran Adhithya (2022). An Investigation of Stochastic and Process-Based Models Describing the Influence of Vegetation and Storms on Barrier Island Dynamics. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198723.