Numerical Modeling and Analysis of Shoreline Change on Galveston Island.

Galveston shoreline data from 1956, 1965, 1990, and 2001 were analyzed with a sediment budget to infer the longshore and cross-shore (out of the littoral system) transport. The analysis indicated a relatively calm period from 1990 to 2001, which was dominated by longshore transport, as well as two hurricane-prone periods (1956-65 and 1965-90), which had both longshore and cross-shore transport. The Wave Information Study wave data (1976-95) were then examined to identify those years where the waves gave the "expected" longshore transport. Five wave years were selected for further study. Numerical modeling of shoreline change on Galveston Island, based on the five selected wave years, was conducted in order to gain an understanding of, and to design remedial action for, an erosional hotspot at the end of the island's seawall. The GENESIS model was chosen after careful consideration of its assumptions and performance and after analysis of site conditions. It was judged to be a suitable shoreline change model for the relatively calm 1990-2001 period, but not for the excessively hurricane-prone 1956-90 period. Model calculations of shoreline change from 1990 to 2001 were in agreement with the measurements in the vicinity of the hotspot. The model was used to design beach nourishment at the hotspot for 2001-11. The calculations indicate that about 100, 000 m³/y of sand would be needed to maintain the 2001 shoreline. Under storm conditions, a sediment budget indicated that an additional 300, 000 m³/y might be necessary to maintain the 2001 shoreline. [ABSTRACT FROM AUTHOR]