Present vs. Future Property Losses From a 100-Year Coastal Flood: A Case Study of Grand Isle, Louisiana

Abstract

Louisiana, U.S.A., is among the world's most vulnerable places to coastal flooding. Increasing frequency/intensity of natural hazards under climate change scenarios is expected to exacerbate Louisiana's coastal flood risk. Although many factors are involved, land subsidence from marshland compaction and underground resource extraction, shoreline erosion accelerated by eustatic sea level rise (ESLR), and tropical-cyclone-induced storm surge are among the most important. While past research has focused on flood risk assessment and mitigation strategies, including climate change scenarios, few studies examine all of these factors collectively. This study shows present pluvial flood depth and the contributions of additional coastal subsidence and ESLR toward future (2050) pluvial flooding. Then, current tropical-storm-induced storm surge and future storm surge depth modeled by Louisiana's Coastal Protection and Restoration Authority (CPRA) under climate change scenarios are presented. Present and future 100-year pluvial flood and storm surge losses (separately, 2020$) to structures and their contents are estimated at the individual building level for Grand Isle, Louisiana, a barrier island town of ecological, economic, historical, recreational, cultural, and aesthetic treasure. Results suggest that the average 100-year pluvial flood depth in buildings will increase by 1.35 feet by 2050, with subsidence contributing over 82% of this total. Subsidence is projected to escalate structure and content losses by ~17% above losses in 2017, while ESLR may contribute ~3% above 2017 losses. A 100-year tropical-cyclone-induced storm surge event amid a “low” scenario of environmental change as defined by CPRA would increase Grand Isle's structure and content losses by 68–74% above the 2017 value by 2027, 141–149% by 2042, and 346–359% by 2067. The (“high”) scenario of environmental change would increase the 100-year storm surge losses by 85–91% above the 2017 value by 2027, 199–218% by 2042, and 407–415% by 2067. Outcomes from this study will offer a more realistic risk assessment model and will direct flood risk managers, property owners, and other stakeholders to build a comprehensive framework to minimize future flood risk in one of the most vulnerable sites in the U.S.A. to coastal flooding.

A data-driven spatial approach to characterize the flood hazard

“…The perilous and expensive nature of flood hazards calls for concurrent improvements in the ability of scientists to measure their risk (Kron, 2005 ). Moreover, rapid increases in the population living in marginal areas relative to the flood hazards (Moulds et al, 2021 ), amid the consequences of land use changes such as in Bangladesh (Dewan et al, 2007 ), Belgium (Akter et al, 2018 ), India (Guhathakurta et al, 2011 ), China (Shen et al, 2021 ), the United States (Qiang et al, 2017 ), and elsewhere, a changing climate (Zhou et al, 2012 ; Kreibich et al, 2015 ), sea level rise (Nicholls et al, 1999 ; Bushra et al, 2021 ), and local factors such as subsidence (Mostafiz et al, 2021a ) and extreme weather events (Guhathakurta et al, 2011 ), underline the urgent need for accelerated improvements in flood risk assessment (Merz et al, 2014 ; Mostafiz, 2022 ). Yet proportionately little advancement has been made.…”

Future crop risk estimation due to drought, extreme temperature, hail, lightning, and tornado at the census tract level in Louisiana

“…of people and assets in high-risk areas, especially along the Gulf of Mexico (Mostafiz et al, 2021a NCEI 2020). With agriculture contributing over $3.1 billion, or 2.9 percent of the state's gross domestic product (University of Arkansas Division of Agriculture 2021), the vulnerability of Louisiana agriculture to weather hazards is substantial, including to the leading crops featured in Tables 2 and 3.…”

“…While loss and risk occur in a wide range of ways, much weather hazard research focuses on property damage (e.g., Mostafiz et al, 2020a;2021a;2021b;2021c;2021d; and casualties (e.g., Jonkman 2005). Although such research is beneficial, the risk posed to agriculture is often ignored.…”

Future Property Risk Estimation For Wildfire In Louisiana, USA

“…While a growing amount of research is focusing on assessing risk due to flood (e.g. Mostafiz et al 2021cMostafiz et al , 2021d, hurricane (e.g. Emanuel et al 2006), tornado (e.g.…”