Bedient, Philip B2022-10-052022-10-052022-052022-04-08May 2022Bahnick, Raychel. "Assessing Land Use Change and Subsidence Impact on Inland Flooding." (2022) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/113510">https://hdl.handle.net/1911/113510</a>.https://hdl.handle.net/1911/113510The greater Houston Area has been exposed to tremendous flooding in recent history (e.g., Hurricane Harvey (2017), Tax Day Flood (2016), Memorial Day Flood (2015)). The destruction and economic loss associated with these major storms highlights the flooding challenges the region faces. These consequences can be further exacerbated by increased land subsidence and urbanization. As watersheds urbanize, the imperviousness increases the runoff volume and peak discharge. There has been limited research on how land subsidence impacts inland flooding at a watershed scale. The goal of the study is to provide decisionmakers with a greater understanding of how the Panther Branch watershed reacts to human induced subsidence and land use change to better inform policy to protect residents in The Woodlands, TX from flooding in the future. This is achieved using remote sensing techniques of local GPS monitoring stations and LiDAR digital elevation models (DEMs) to analyze land deformation due to subsidence. A two-dimensional hydrodynamic model of a projected urbanized watershed was created and calibrated to historical storms. Cumulative land subsidence is highly correlated with past population growth in The Woodlands. Subsidence was linearly extrapolated about 50 years into the future. This study found that projected subsidence in year 2070 lowered 100-year storm water surface elevation in the channel about 1.4 feet, proportional to the projected subsidence of the watershed (1-2 feet). Both drivers, subsidence and land use, had minimal impact (less than 5%) on floodplain extent. Land use change increased peak discharge in the downstream channel by 39-55%. Flood depths increased significantly outside the channel due to subsidence which cause increased inundation of major roadways and neighborhood streets. During 100-year storm, neighborhood streets experienced an increase of approximately 4-6 inches of flood depth and major roads were inundated by up to an additional 14 inches. Currently, the Woodlands is subsiding 0.2-0.7 inches per year and the threat of subsidence is projected to increase due to local groundwater pumping. Local population is projected to increase 42%, increasing development and water demand. This study provides valuable information for water managers and decisionmakers about the hazardous flood implications subsidence and urbanization can induce.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.flood risksubsidenceland use changeinland floodingThesis2022-10-05