Flood exposure and structure damage under deterministic design-storm and stochastic storm transposition rainfall scenarios: a case study in South Louisiana, USA
- 1Department of Civil Engineering, University of Louisiana at Lafayette, Lafayette, 70504, USA
- 2Louisiana Watershed Flood Center, University of Louisiana at Lafayette, Lafayette, 70504, USA
- 3Irrigation and Hydraulics Engineering Department, Faculty of Engineering, Cairo University, P.O. Box 12211, Giza 12613, Egypt
Abstract
Flood hazard maps and damage estimates guide floodplain management, mitigation planning, and engineering design, but they commonly rely on rainfall frequency analysis to define annual exceedance probability (AEP) storms, commonly referred to as design storms. Current engineering practice typically employs spatially uniform design storms derived from point-based gauge statistics; however, this approach suppresses the spatial organization and intensity gradients present in observed storms. Stochastic storm transposition (SST) offers an alternative by preserving the spatial structure of observed rainfall and stochastically repositioning full storm fields across a watershed. This study compares flood exposure and damage produced by Atlas 14 and SST rainfall representations in the Vermilion River Basin, a low-gradient inland–coastal watershed in south-central Louisiana. Although the TP40-adjusted Atlas 14 rainfall depth was larger than the mean basin-average SST accumulation across the 50 realizations (310 mm vs. 238.1 mm), the SSTmax composite produced substantially greater total structure damage than the baseline Atlas 14 scenario (USD 0.923 billion vs. USD 0.477 billion). Moreover, the comparison identified 11 518 buildings that were inundated in at least one SST realization but not under Atlas 14, representing more than USD 110 million in cumulative structural damage. The divergence between the two approaches is concentrated in mid-elevation urban neighborhoods, where spatial rainfall variability can cross local inundation thresholds that were not crossed under the spatially uniform storm. These results show that, in the VRB, the spatially uniform Atlas 14 design storm missed localized flood exposure that emerged when storm placement and rainfall spatial variability were represented.
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BibTeX
@article{elsaadani2026flood,
title = {{Flood exposure and structure damage under deterministic design-storm and stochastic storm transposition rainfall scenarios: a case study in South Louisiana, USA}},
author = {M. ElSaadani and M. ElSaadani and E. Habib and E. Habib and M. M. Morsy and M. M. Morsy},
journal = {Natural Hazards and Earth System Sciences},
year = {2026},
month = oct,
doi = {10.5194/nhess-26-5201-2026},
url = {https://doi.org/10.5194/nhess-26-5201-2026},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Flood exposure and structure damage under deterministic design-storm and stochastic storm transposition rainfall scenarios: a case study in South Louisiana, USA
AU - M. ElSaadani
AU - M. ElSaadani
AU - E. Habib
AU - E. Habib
AU - M. M. Morsy
AU - M. M. Morsy
PY - 2026
DA - 2026/10/23
JO - Natural Hazards and Earth System Sciences
DO - 10.5194/nhess-26-5201-2026
UR - https://doi.org/10.5194/nhess-26-5201-2026
AB - Flood hazard maps and damage estimates guide floodplain management, mitigation planning, and engineering design, but they commonly rely on rainfall frequency analysis to define annual exceedance probability (AEP) storms, commonly referred to as design storms. Current engineering practice typically employs spatially uniform design storms derived from point-based gauge statistics; however, this approach suppresses the spatial organization and intensity gradients present in observed storms. Stochastic storm transposition (SST) offers an alternative by preserving the spatial structure of observed rainfall and stochastically repositioning full storm fields across a watershed. This study compares flood exposure and damage produced by Atlas 14 and SST rainfall representations in the Vermilion River Basin, a low-gradient inland–coastal watershed in south-central Louisiana. Although the TP40-adjusted Atlas 14 rainfall depth was larger than the mean basin-average SST accumulation across the 50 realizations (310 mm vs. 238.1 mm), the SSTmax composite produced substantially greater total structure damage than the baseline Atlas 14 scenario (USD 0.923 billion vs. USD 0.477 billion). Moreover, the comparison identified 11 518 buildings that were inundated in at least one SST realization but not under Atlas 14, representing more than USD 110 million in cumulative structural damage. The divergence between the two approaches is concentrated in mid-elevation urban neighborhoods, where spatial rainfall variability can cross local inundation thresholds that were not crossed under the spatially uniform storm. These results show that, in the VRB, the spatially uniform Atlas 14 design storm missed localized flood exposure that emerged when storm placement and rainfall spatial variability were represented.
SN - 1561-8633
SN - 1684-9981
ER -