Urbanization Impacts on Flooding in the Kansas River Basin and Evaluation of Wetlands as a Mitigation Measure

Abstract

This study evaluates the impacts of future land use changes on flooding in the Kansas River basin. It also describes the impacts of wetlands on flood reduction. The study presents Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) based runoff modeling and Hydrologic Engineering Center River Analysis System (HEC-RAS) based flood analysis results for SCS 100-year, 24 h design storms over the next 30 years. Land use changes in the basin mainly consist of gradual urbanization and densification from low to high intensity urban development by 2040. The models were calibrated and validated for past events and then run for future land use scenarios (2020, 2030, and 2040). The future land use scenarios were developed using GIS. Results demonstrate an appreciable increase in peak discharge and flood inundation extents for the future scenarios. From the baseline scenario to the 2040 scenario, for the different storms, there was a 10% to 19% increase in peak discharge, a 2% to 7% increase in water elevations, and a 5% to 8% increase in inundation area. A considerable reduction in peak discharges and inundation extents was achieved after the wetland area was increased to 6%, 8%, and 10% from the original 5% for the 2020, 2030, and 2040 scenarios, respectively. There was a 12% to 18% decrease in peak discharge, a 1% to 15% decrease in water elevations, and a 15% to 19% decrease in inundation area. This research demonstrates the importance of including wetlands in designing flood mitigation alternatives.