SGER: Spatial Patterns of Flood Sedimentation in Response to an Extreme Event: Guadelupe River, Texas

University Of Texas At Austin, Austin TX

Investigators

Abstract

Although floodplain research has been a mainstay of fluvial geomorphology, much is not known about the importance of large flood events to floodplain construction. This is particularly significant with respect to the interpretation of the influence of climate change (both in the past and looking ahead to the future) on drainage systems, because flood deposits serve as proxy evidence for flooding and landscape response. Humid coastal plain fluvial systems have been studied intensively, but the semi -arid and arid drainage systems of Texas may be particularly sensitive to large rainfall events, and far less research has been devoted to floodplain processes in these settings. This Small Grant for Exploratory Research will support a project that investigates flood sedimentation in the Guadalupe River valley of east central Texas, which experienced an extreme flood event in early July 2002. The project considers the influence of downstream drainage basin controls on the pattern and character of flood deposits. Most of the project will be field based, with supplemental data obtained from USGS 1:24,000 topographic maps and digital orthophotos. The thickness of the flood deposits will be measured in the field, and particle size analysis of flood sediments will occur in the University of Texas geomorphology laboratory. Total-stations surveying will be used for mapping the floodplain topography and location of sediment samples. The drainage basin controls on flood sedimentation will be examined by considering the floodplain topography, valley dimensions (gradient and width), flood regime (discharge, stage, length of inundation), and the planform channel morphology. The influence of riparian vegetation on sedimentation will be considered by comparing the canopy cover and tree density within each site, and between sites. The project is expected to contribute theoretically to understanding of the importance of large events to floodplain construction. It will assess how various controls influence the spatial dimensions of flood deposits (volume and particle size). Regionally, the project will increase understanding of floodplain sedimentation in western Gulf Coastal Plain fluvial systems.. this project will provide valuable opportunities for student involvement in the fieldwork, and through follow-up activities, it will enable the investigator to be more effective in teaching fundamental field techniques, fluvial geomorphology, and analytic approaches using geographic information systems. The project also will yield data that may prove to be quite useful for local officials as they plan future flood-prevention and -control strategies.