Abstract:
The Texas coast is vulnerable to sea level rise and coastal flooding because it is a low-lying coastal plain with gently sloping topography and eroding coastal environments. In addition, local land surface subsidence is increasing the risk of sea level rise by enhancing the reach of storm surges and tides further inland. Furthermore, it is estimated that the population living within Texas’ 18 coastal counties will increase by 52% from 2010 to 2050, reaching 9.3 million. Given the increasing vulnerability of the Texas coast, this study assesses the impacts of sea level rise and associated enhanced storm surge to better understand the relative susceptibility to negative impacts on the natural and built environments.
This study is part of the second publication of the Texas Coastal Resiliency Master Plan (TCRMP), an ambitious coastal planning effort by the Texas General Land Office (GLO) to make the Texas coast more resilient to hazards. This study employs the Sea Level Affecting Marshes Model (SLAMM) to project the possible effects of sea level rise on coastal habitats under 1 meter of global sea level rise scenario by year 2100. The relative component of sea level rise is determined on a regional basis by deriving an average trend from long-term records of coastal tide gauges.
The coupled hydrodynamic storm surge model, Advanced CIRCulation (ADCIRC) and Simulating Waves in the Nearshore (SWAN), is used to identify the threats posed by storm surge and nearshore waves to people and the ecosystem in the current and 2100 environments. Six synthetic Category 2 hurricanes making landfall near to the major bay systems or city centers across the Texas coast are modeled with ADCIRC+SWAN for both current and 2100 environments. The 2100 surface and land cover predicted by SLAMM is used as a representative of future elevations and land cover type for input to the ADCIRC+SWAN model.
Results from this study will help state, local, and federal decision makers understand the value provided by the coast, the inherent risks the coastal communities face, and the opportunities available to manage a dynamic coastal environment in a more resilient manner.
Suggested Citation:
Dotson, Marissa, Mukesh Subedee, and Jim Gibeaut. 2023. Geospatial model output of land cover change and storm surge impacts under projected sea level rise and category 2 hurricanes along the Texas Coast. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/K1BVN6Q3
Purpose:
The Texas coast is vulnerable to sea level rise and coastal flooding because it is a low-lying coastal plain with gently sloping topography and eroding coastal environments. In addition, local land surface subsidence is increasing the risk of sea level rise by enhancing the reach of storm surges and tides further inland. Furthermore, it is estimated that the population living within Texas’ 18 coastal counties will increase by 52% from 2010 to 2050, reaching 9.3 million. Given the increasing vulnerability of the Texas coast, this study assesses the impacts of sea level rise and associated enhanced storm surge to better understand the relative susceptibility to negative impacts on the natural and built environments.
This study is part of the second publication of the Texas Coastal Resiliency Master Plan (TCRMP), an ambitious coastal planning effort by the Texas General Land Office (GLO) to make the Texas coast more resilient to hazards. This study employs the Sea Level Affecting Marshes Model (SLAMM) to project the possible effects of sea level rise on coastal habitats under 1 meter of global sea level rise scenario by year 2100. The relative component of sea level rise is determined on a regional basis by deriving an average trend from long-term records of coastal tide gauges.
The coupled hydrodynamic storm surge model, Advanced CIRCulation (ADCIRC) and Simulating Waves in the Nearshore (SWAN), is used to identify the threats posed by storm surge and nearshore waves to people and the ecosystem in the current and 2100 environments. Six synthetic Category 2 hurricanes making landfall near to the major bay systems or city centers across the Texas coast are modeled with ADCIRC+SWAN for both current and 2100 environments. The 2100 surface and land cover predicted by SLAMM is used as a representative of future elevations and land cover type for input to the ADCIRC+SWAN model.
Results from this study will help state, local, and federal decision makers understand the value provided by the coast, the inherent risks the coastal communities face, and the opportunities available to manage a dynamic coastal environment in a more resilient manner.
Methods:
To facilitate the presentation of Issues of Concern and potential solutions, the Texas coast was divided into four regions. The four regions are based on major bay systems and habitats: Region 1 extends from Sabine Pass to Galveston Bay covering Brazoria, Chambers, Galveston, Harris, Jefferson, and Orange counties; Region 2 surrounds the entire Matagorda Bay system covering Calhoun, Jackson, Matagorda and Victoria counties; Region 3 extends from San Antonio Bay to the Baffin Bay covering Aransas, Kleberg, Nueces, Refugio, and San Patricio counties; and Region 4 extends from southern edge of Baffin Bay to the Texas-Mexico border covering Cameron, Kenedy, and Willacy Counties. Due to high population density, Region 1 was subdivided into Regions 1A (from the Sabine River to the west side of Galveston Bay) and 1B (from the west side of Galveston Bay to the Brazos River).
Several map-based inputs and numeric parameters along with a 1 m global mean sea level rise scenario (GMSLR) by the year 2100 were required to run the SLAMM model that simulates the dominant processes involved in wetland conversion and shoreline change for the SLR scenario. SLAMM provides maps of updated elevations and land cover classes in the year 2100 along with other numerical outputs. The future topographic surface predicted by the SLAMM model was used to update the ADCIRC+SWAN model computational mesh. The future land cover conditions predicted by the SLAMM model, combined with the 2100 land cover datasets developed by the US Geological Survey (Sohl et al., 2014), was used to generate ADCIRC+SWAN model friction parameters (Manning’s n) representative of future conditions. The GMSLR scenario of 1 m by 2100 was incorporated in the ADCIRC+SWAN model setup by increasing the initial water surface elevation from the current sea level condition.
The ADCIRC+SWAN model was forced using meteorological wind and pressure fields of six selected hypothetical Category 2 hurricane events making landfall in different parts of the Texas coast. A total of 14 ADCIRC+SWAN simulations were performed. The same six hurricane events were forced to both the present-day condition to assess the storm surge impact in present land cover and topography, and the future condition (2100) to assess the combined impact of RSLR and future land cover and topography. In addition, two storms were modeled with simulated resiliency projects in the future condition to assess how these projects can change storm surge patterns in comparison to the future landscape without any resiliency projects along the coast. For more information on the models, input data, modeling scenarios, and methodology, please refer to the 2019 TCRMP technical report (Subedee et al., 2019).
Provenance and Historical References:
Sohl, T.L., Sayler, K.L., Bouchard, M.A., Reker, R.R., Friesz, A.M., Bennett, S.L., Sleeter, B.M., Sleeter, R.R., Wilson, T., Soulard, C. and Knuppe, M., 2014. Spatially explicit modeling of 1992–2100 land cover and forest stand age for the conterminous United States. Ecological Applications, 24(5), pp.1015-1036.
Subedee, M., C. R. Pollard, M. Dotson, B. Lupher, L. Su and J. Gibeaut. 2019. Sea Level Rise and Storm Surge Modeling in support of the 2019 Texas Coastal Resiliency Master Plan (TCRMP). Final technical report to the Texas General Land Office, Contract Number 17-244-000-A189. Harte Research Institute, Corpus Christi, Texas, USA, 162 pp.
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