This CAREER project aims to advance understanding and predictive capability of sediment transport processes occurring in the swash zone through laboratory and field efforts using a new measurement device for sediment transport in the bedload layer (very near the at-rest bed level). The swash zone is the area near the shoreline where wave-driven flows alternately wash up and down the beach face and ultimately expend their energy. Thus, swash processes are one of the fundamental mechanisms by which coastal morphological change happens (e.g. shoreline response to changing sea level). With much of the population living near the coastline, global sea levels rising at a rate of 3 mm/yr over the last decade (IPPC WGII, 2007) and nearly 85% of sandy U.S. coastlines eroding (Thornton et al., 2000), there is a real societal demand for better understanding of these proceses. Current predictive models are extremely limited by their inability to accurately characterize the significance of bedload transport. This limitation is primarily due to the fact that no reliable measurements of time-dependent bedload transport exist, even though time-integrated trap data demonstrates that bedload is often the dominant transport mode (Horn and Mason, 1994).
This project will approach the difficult task of quantifying swash-zone bedload transport with the following steps:
(1) test and use a novel bedload sensor to obtain elusive bedload measurements in the swash zone; (2) quantify the relative importance of bedload and suspended load as a function of beach slope, wave conditions and swash phase to develop new sediment transport formulations; (3) investigate the role of sediment advection and exchange across the surf/swash boundary in the swash-zone sediment transport signal; and (4) utilize laboratory and field data to reliably parameterize swash-zone sediment transport.
The result will be an improved understanding of the role of bedload transport in reshaping the beach face leading to enhanced predictions of coastal morphologic change and the design of more effective and economical mitigation procedures.
Broader Impacts: This study will broaden understanding of the physics of coastal sediment transport and will lead to significant improvement in the ability to predict coastal phenomena such as beach erosion and beach nourishment performance. More generally, the measurement techniques and data sets will greatly improve scientific understanding of particle-laden boundary layer processes that are of broad interest in the area of fluid mechanics. Research results will be disseminated to engineers and lay people through integrated and ongoing outreach activities. The University of Delaware's Engineering Outreach Office, local school teachers and education curriculum experts will collaborate and assist in initiating the "beach in a classroom" outreach program for high school students and teacher training workshops using a 16-foot portable wave flume. The study will support a minority undergraduate summer intern in performing research side-by-side with faculty and graduate students. Recruitment for the internship will be conducted at nearby HBCU's through collaboration with the NSF-sponsored LSAMP Program.
