Modeling Flood Risks for Small-Scale Coastal Watershed Across Shared Socioeconomic Pathway Scenarios

Author

Sebastian Loschner, University of South AlabamaFollow

Date of Award

12-2025

Document Type

Thesis

Degree Name

M.S.

Department

Civil, Coastal, and Environmental Engineering

Committee Chair

Bret M. Webb, Ph.D.

Abstract

Coastal flooding, driven by the mixture of natural processes and human activities such as precipitation, waves, sea level rise, and urbanization, remains a growing concern. While recent flood-risk studies use IPCC's Shared Socioeconomic Pathways with climate projections to assess future flood exposure, smaller coastal watersheds, < 120,000 acres, remain insufficiently studied. Projected sea level rise is expected to intensify these impacts in smaller systems, potentially causing more severe flooding than reported for larger watersheds. To address this gap, this study used the SRH-2D model integrated with Aquaveo's Surface-water Modeling System to simulate flooding in the lower Fish River basin, Alabama. A coastal watershed sensitive to both riverine and tidal influences. Simulations tested different sea levels based on SSP scenarios corresponding to low, moderate, and high emissions for the years 2050 and 2100. Results indicate that the midcentury scenarios remained even in inundation extent and volume, between 9.9-10.4% compared to the 2020 baseline, the latter scenarios had a wider range in results of between 25.9-50.3% compared to the same baseline. Across scenarios, the most vulnerable and inundated areas of the smaller coastal watershed were the narrow points where upstream flow convene with downstream backwater. These findings highlight the need for futuristic location-specific flood mitigation strategies.

Recommended Citation

Loschner, Sebastian, "Modeling Flood Risks for Small-Scale Coastal Watershed Across Shared Socioeconomic Pathway Scenarios" (2025). Graduate Theses and Dissertations (2019 - present). 239.
https://jagworks.southalabama.edu/theses_diss/239