Modelling the morphodynamic evolution of Galveston beach, Gulf of Mexico, following Hurricane Ike in 2008

摘要

A unique set of field measurements taken along Galveston beach have been compiled to give annual shoreline positions over the period 2010-2016. These have been used, in conjunction with statistical and mathematical modelling, to gain insights into the response of the shoreline after the landfall of Hurricane Ike in 2008, which caused extensive erosion and loss of material from the beach. Over the period 2010-2014, a generally accretive trend is observed along the beach. Within this trend, two different patterns are evident. In the area extending westward of South Jetty the accretion rate is fast until April 2011, after which the accretion rate decreases. The remainder of the beach, including the groyne field in front of the city of Galveston, exhibits the greatest accretive trend after April 2011. It is hypothesized that distinct sandbanks lying offshore of Galveston Island were formed during the passage of Hurricane Ike and control these two different patterns of recovery. To test this hypothesis a novel 1-line model, based on linked analytical solutions, was set up to investigate the beach response to various sediment source distributions. The model was tested against existing survey measurements and performed satisfactorily. An exploration of various sediment supply scenarios with the model supports the hypothesis that offshore sediment stores, one distinct source to the south of South Jetty and a diffuse linear source running the length of the groyne field and seawall, were gradually being fed back to the beach by the prevailing wave conditions.