Abstract:

The Texas coast is a system of barrier islands, lagoons, estuaries, plains, and rivers on a low-lying coastal plain with gently sloping topography. Embedded in this natural and dynamic system are a variety of human developments and activities including oil and gas production, heavy industry, shipping, commercial fishing, recreational fishing, agriculture, tourism, and small and large communities dotted throughout the landscape. The natural systems of the coastal plain, however, are dynamic and subject to sudden hazards such as floods, storm winds, storm surge, and erosion superimposed on longer-term processes of ongoing erosion caused by sediment supply changes, shifting habitats, sea level rise (SLR), and climate change. Given the vulnerability of the Texas coast, this study assessed the impacts of relative sea level rise (RSLR) and associated enhanced storm surge to better understand the relative susceptibility to negative impacts on the natural and built environments. This study was part of the third publication of the Texas Coastal Resiliency Master Plan (TCRMP) published in April 2023. TCRMP is an ambitious coastal planning effort by the Texas General Land Office (TGLO) to make the Texas coast more resilient to hazards. For this study, the Harte Research Institute (HRI) developed a dynamic modeling framework to assess quantitative information regarding the impacts of SLR and associated enhanced future storm surge caused by higher sea levels and changes in land cover. For the 2023 TCRMP, two SLR scenarios are modeled - Intermediate-Low scenario (0.5 m of SLR by 2100) and Intermediate-High scenario (1.5 meters of SLR by 2100). The relative component of sea level rise was determined on a regional basis by deriving an average trend from long-term records of coastal tide gauges. Similarly, nineteen synthetic storms, ranging in severity from Category 1 to 3, making landfall near major bay systems or city centers across the Texas coast, are modeled for both the current and 2100 landscapes. The coupled hydrodynamic storm surge model, Advanced CIRCulation (ADCIRC) and Simulating Waves in the Nearshore (SWAN) was used to identify the threat posed by storm surge and nearshore waves to communities and the coastal ecosystem in both the current and 2100 landscapes. To better understand the relative vulnerability to storm surge from the full variety of modeled storms, a storm surge vulnerability map was developed by considering simulated storm surge inundation of all modeled storms in the present and future landscape scenarios. A total of 57 storm simulations are run with 19 selected storms in the present landscape condition and two future landscape conditions. The maximum water surface elevation (MAXELE) obtained from these 57 simulations was considered to develop the storm surge vulnerability map. To calculate the storm surge vulnerability score along the Texas coast in all these 57 simulations, each node in the computational mesh is examined to find out how many times it is inundated in the 57 simulations. Finally, a storm surge vulnerability index raster of range 0 - 1 was developed, where a value of 1 is inundated in all 57 scenarios, and 0 is not inundated in any scenarios. This raster map shows the spatial coverage of potential storm surge flooding vulnerability along the Texas coast.

Suggested Citation:

Subedee, Mukesh, Pu Huang, and James Gibeaut. 2023. Storm surge vulnerability map of the Texas coast considering two projected sea level rise scenarios. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/hqtj13qm

Purpose:

The low-lying and gently sloping Texas coastal plain is highly vulnerable to storm surge and waves caused by hurricanes. Storm surge is also one of the top vulnerabilities listed by the Technical Advisory Committee (TAC) members who provide critical input throughout the entire planning process. Furthermore, the storm surge risk assessment provides the basis for risk mitigation and related decision-making for adaptation and resilience. Therefore, it is both sensible and imperative to understand the storm surge vulnerability of the Texas coast.

Data Parameters and Units:

The vulnerability map has a value ranging from 0 - 1, where the highest vulnerability (value 1) in these maps shows an area inundated in all storm scenarios, and the lowest vulnerability (value 0) shows an area not being inundated due to the storm surge in any scenario.

Methods:

A total of 57 ADCIRC+SWAN model simulations were forced using meteorological wind and pressure fields for each of the nineteen hurricane events. The nineteen hurricane events were simulated on the present landscape, and again on the two future 2100 landscapes - Intermediate Low (0.5 m of GSLR by 2100) and Intermediate High (1.5m of GSLR by 2100). The maximum water surface elevation (MAXELE) was derived for each storm simulation and analyzed along the whole Texas coast which resulted in 57 MAXELE scenarios. To calculate the storm surge vulnerability score along the Texas coast using these 57 scenarios, each node in the computational mesh is examined to find out how many times it is inundated in the 57 scenarios. It is then divided by the total 57 scenarios considered to obtain the storm surge vulnerability normalized index of the range 0 - 1, where a value of 1 means an area is inundated in all 57 scenarios, and 0 means it is not inundated in any scenarios. Once the index value in the range of 0 – 1 is assigned to each node in the computational mesh, a storm surge normalized vulnerability index raster was generated using Kernel Smoothing interpolation.

Individual Files: