Application of HEC-HMS, HEC-RAS and GIS to a Large-Scale Watershed in Support of Flood Vulnerability Assessment, Great Miami Watershed, OH

Date of Award

5-9-2026

Degree Name

M.S. in Interdisciplinary Studies

Department

Department of Earth and Environmental Geosciences

Advisor/Chair

Chia-Yu Wu

Abstract

Floods represent one of the most destructive natural hazards globally, causing significant economic losses, infrastructure damage, and loss of life. This study focuses on integrating hydrological, hydraulic, and geospatial modeling technologies to simulate rainfall-runoff processes and predict flood extent for the Great Miami River watershed, historically impacted by severe flooding events such as the catastrophic 1913 Great Dayton Flood. The study incorporated 34 subbasins, 18 reaches, and 4 major reservoirs (Englewood, Taylorsville, Lockington, and Huffman) managed by the Miami Conservancy District. The HEC-HMS model demonstrated excellent calibration and validation performance with Nash-Sutcliffe Efficiency (NSE) values exceeding 0.64, ratio of the root mean square error to the standard deviation ratio (RSR) less than 0.60 and coefficient of determination (R2) exceeding 0.85 at gauging stations, confirming model reliability and accuracy for estimating peak flow and evaluating the performance of reservoirs. Following calibration and validation, the model was utilized to simulate the 1913 storm event, yielding a peak discharge of 174,663.42 cfs at the watershed outlet. Results demonstrate that the four reservoirs significantly attenuated peak flows, with Lockington reservoir reducing inflows by 38.98%, Huffman by 9.45%, Taylorsville by 9.13% and Englewood by 3.82% to their downstream, substantially demonstrating the effectiveness of flood control infrastructure. HEC-RAS 2D modeling incorporated high-resolution digital elevation models (2.5 × 2.5 feet) and Flood Insurance Study data as boundary conditions, producing detailed hydraulic parameters including water surface elevation, flow depth, and flow velocities in floodplain areas for the 100-year design event. The model validation achieved by comparing the computed water surface elevation against regulatory Flood Insurance Study data and satellite imagery and confirmed high spatial agreement (±0.5 ft). By integrating the HEC_RAS result with the ArcGIS, the 100-year design flood event inundated 32.21 square miles of floodplain area, including 12.34 square miles of agricultural land, 9.12 square miles of residential area, 5.53 square miles of forest land, and 5.22 square miles of perennial water body. This integrated framework successfully identifies flood-prone areas, evaluates structural flood mitigation measures, and produces spatially explicit inundation maps.

Keywords

Geographic Information Science, Hydrologic Sciences, Hydrology

Comments

OCLC No. 1591829753

Rights Statement

Copyright 2026, author.

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