Role of Free and Forced Boundary Conditions on Beachface Evolution

Texas A&M University, College Station TX

Investigators

Abstract

This research project will examine how the evolution of the nearshore profile determines beachface erosion and accretion through changes in both the supply and transport of sediment within the swash zone. The lack of information about this set of processes remains a central barrier to the development of theories regarding coastal evolution and beach-dune interaction that can be translated across scales and field sites. Most swash zone studies have considered hydrodynamics and transport without explicit consideration of the beach-state in which the field observations were collected and the dynamic nature of this boundary condition. In this project, the researchers will assess how swash-zone hydrodynamics and sediment transport are dependent on the transformation of the incident wave field across the evolving nearshore profile. The project will involve a complex field-study that simultaneously monitors swash-zone hydrodynamics, sediment transport, and bed elevation change in response to changes in beach-state and nearshore morphology. Field instruments that will be used include ultrasonic distance sensors and current meters in the swash zone, wave and tide sensors in the inner-surf zone, and a terrestrial laser scanner and remote cameras to monitor beachface evolution. The project is expected to yield a rich dataset of evolving swash-zone hydrodynamics and sediment transport in response to changes in the nearshore profile, an important and unique first step to developing a predictive model of beachface evolution. The impact of a tropical storm or hurricane on a barrier island is dependent on the ability of the beach and dune system to recover since the last storm. The recovery of dunes is dependent on the transfer of sediment from the nearshore to the beachface, where it may become available for aeolian transport to the backshore and dunes. The factors that control the rate and mechanism of swash-zone evolution therefore are of great interest to coastal managers who need improved information and models for predicting the type of impact expected during succeeding storms and for determining whether beach or dune restoration is required to protect property and infrastructure. This project also will provide valuable education and training for a promising graduate student.