Date of Award
6-26-2026
Date Published
August 2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil and Environmental Engineering
Advisor(s)
Elizabeth Carter
Subject Categories
Civil and Environmental Engineering | Civil Engineering | Engineering
Abstract
Earthquakes can cause rapid changes in elevation and topographic relief, which, in turn, affect hydrologic regimes and modify flood risk in affected regions. The regulatory floodplain, an area of elevated flood hazard adjacent to water bodies, is critical for managing exposure and mitigating flood risk in many nations. Shifts in the distribution of flood risk in regions impacted by seismic activity constitute a compound hazard. Tools are needed to enable the reevaluation of regulatory flood maps after seismic events to minimize the exposure of affected populations to additional flood hazard. This study presents a workflow for rapidly updating regulatory flood maps in regions exposed to topographic shifts from earthquakes, using globally available observations and open-source processing tools. Flood inundation maps for the fluvial flood system of the South Fork Kern River, California, USA, were performed using the HEC-RAS hydrodynamic model. Accurate topographic data representing the bare-earth ground surface is vital for precise flood simulations. So, the United States Geological Survey’s (USGS) National Elevation Dataset (NED) at 1/3 arc-second (~10m) resolution was used as topographic input data in the HEC-RAS model. These flood maps were updated after a series of high-magnitude earthquakes by incorporating vertical displacement estimated from interferometric synthetic aperture radar (InSAR) time series of the Sentinel-1A/B constellation. The InSAR-updated DEMs were validated using in situ global positioning station networks, and the accuracy of InSAR-updated flood maps was validated using inundation extents observed by high-resolution optical satellite imagery during pre- and post-earthquake events of similar discharge. The maximum line-of-sight displacement post-earthquake within the study area was -75.80 cm (subsidence) and 98.30 cm (uplift). Validation of the InSAR line-of-sight displacement against line-of-sight displacements measured with ground-based global positioning system (GPS) stations yielded a correlation coefficient of 0.85 and a root-mean-square error of 1.57 cm/year. Analyzing three reaches along the Kern River using the HEC-RAS for pre- and post-earthquake DEMs revealed that the simulated flood extents resulted in higher flood extents for the post-earthquake DEM than those based on the pre-earthquake DEM across all three study reaches. The inundated areas increased at the 100- year return period by 0.25 km², 0.48 km², and 0.40 km² for reaches one, two, and three, respectively. The validation of the simulated flood extents indicated that the post-earthquake DEM showed better agreement with the observed flood extents from high-resolution optical satellite imagery. The post-earthquake scenario achieved F1-scores of 63.3%, 84.52%, and 82.4% for reaches one, two, and three, respectively, at optimal NDWI thresholds of -0.45, -0.35, and -0.30. Implications for post-earthquake flood hazard re-evaluation reconnaissance are discussed.
Access
Open Access
Recommended Citation
Al Amry, Nariman Hassan, "Assessing Fluvial Flood Risk Changes Using an InSAR-Updated Digital Elevation Model Post-Earthquake" (2026). Dissertations - ALL. 2340.
https://surface.syr.edu/etd/2340
