Assessing the Effectiveness of Floodplain Modifications for Flood Mitigation in Swatara Creek, PennsylvaniaPillay, Anushka Environmental EngineeringNature-Based SolutionsFlood MitigationHydraulic ModelingEnvironmental Systems EngineeringB SCommunities across Pennsylvania are experiencing more frequent and intense flooding as extreme precipitation events continue to rise. In response, nature-based solutions (NBS), including floodplain terrain modification and vegetation-based land cover change, have gained attention as alternatives to traditional flood control strategies. However, few studies examine how these two floodplain modifications perform in combination. This study uses a 2D HEC-RAS hydraulic model to evaluate the effectiveness of combined floodplain terrain extraction and vegetation-based roughness modifications across seven sites along Swatara Creek, Pennsylvania. Three extraction depths (3, 5, and 10 ft) and three Manning's n values (0.027, 0.045, and 0.08) were tested under both low- and high-discharge conditions, producing 18 modified scenarios compared against 2 unmodified baseline. Results indicate that all modified scenarios reduced flood extent relative to the baseline, with percent reductions ranging from 6.01% to 15.77%. Overall, terrain extraction emerged as the strongest control on flood reduction, with larger extractions consistently yielding greater percent reductions. Manning’s n had a relatively modest influence, with lower roughness values generally contributing to slightly improved outcomes. These findings support combined floodplain modification as a viable nature-based mitigation strategy and provide a foundation for more targeted floodplain management along flood-prone watersheds in central Pennsylvania.Lauren Mc Phillips, Thesis SupervisorJeremy Michael Gernand, Thesis Honors Advisoropen_access2026-04-14T16:23:02Zhttps://honors.libraries.psu.edu/catalog/10212ajp7201