RAPID: Analysis of the May 2015 Texas Flood with a Connectivity Framework and High Resolution Topography Data

University Of Texas At Austin, Austin TX

Investigators

Abstract

After four years of severe drought, central Texas experienced massive flooding on 25-26 May 2015. It is now clear that an event of this magnitude had never been recorded before, with monthly precipitation totals reaching 20 inches at several locations. The 25-26 May event alone contributed 10 inches of rain. The number of rivers in flood was enormous as was the spatial extent of the affected areas spanning the entire central portion of Texas from major city centers such as Austin and Houston to smaller towns such as Wimberley and Bastrop. This proposal seeks immediate acquisition of high-resolution topography data using airborne remote-sensing technology to assess the impact of the Memorial Day Floods. The data will be acquired by the National Center for Airborne Laser Mapping at the University of Houston. Data analysis will be conducted at the University of Texas at Austin. The objective of the proposed research is to quantify the hydrological and sedimentological connectivity between river channel and floodplain during this extreme event and its impact on downstream sediment transport. Such knowledge is fundamental for informing sustainable catchment management through better understanding of where erosion and sedimentation will occur during major storm events. The data collected for this project will immediately be made publically available and shared with the engineering community to aid in assessing the structural damage to bridges and dams impacted by the floods. The data will also be used in a case study to train 46 graduate students at a 2015 Summer Institute that is part of the National Flood Interoperability Experiment. The team will test a hypothesis that channel-floodplain connectivity influences downstream sediment transport, and in particular that high channel-floodplain connectivity resulted in reduced downstream sediment transport due to sediment dispersal and storage on the floodplain. To test this hypothesis, the study targets two contrasting areas: the Lower Trinity River--a major meandering river in Texas where sediment transport is the subject of ongoing research, and an urban setting in downtown Austin. Both experienced major flooding conditions during the May 2015 event, but their floodplains are quite different. Analytical work will use the topography analysis tool GeoNet in conjunction with post-flood fieldwork and enhancement of simulation and forecasting models used in the National Flood Interoperability Experiment. The data will be stored in the NSF-funded OpenTopography repository for access by the community at large. Research results will be disseminated through open-access publications and conference presentations, and the tools used as part of the analysis are available to the community in open-source format.