Wetland transformations for three relative sea-level rise scenarios along the middle and upper Texas Coast, wetland current condition map and wetland transformation maps by decade, sea-level rise scenario, and coastal wetland drowning threshold

As sea levels rise, wetlands can adapt to changing conditions through vertical development (that is, soil surface elevation gains via biophysical feedbacks) and horizontal migration into upslope areas. Elevation-based models of wetland transformation from sea-level rise are often hampered from a variety of sources of uncertainty, including contemporary elevation and water levels and future water levels from sea-level rise. This data release includes geospatial data products that utilize Monte Carlo simulations to address these sources of uncertainty and highlight potential wetland transformations under various relative sea-level rise scenarios along Texas' middle and upper coast. This data release includes the current extent of coastal wetlands and decadal maps of coastal wetland transformation from 2030–2100 for three relative sea-level rise scenarios — Intermediate-low, Intermediate, and Intermediate-high — from an interagency sea-level rise report published in 2022 (Sweet and others, 2022). Datasets in this release include the following classes: 1) Upslope (that is, areas that are above the National Oceanographic and Atmospheric Administration’s (NOAA) moderate high tide flooding threshold; Sweet and others, 2022); 2) Irregularly oceanic-flooded wetlands (that is, wetlands that are flooded by oceanic water less frequently than daily [that is, below the NOAA moderate high tide flooding threshold and above the mean high water datum]); 3) Regularly oceanic-flooded wetlands (that is, wetlands that are flooded by oceanic water daily [that is, below the mean high water datum and above the mean lower low water datum] and generally fell in the upper two-thirds of this wetland zone based on elevation); 4) Converting to open water (that is, wetlands that are flooded by oceanic water daily [that is, below the mean high water datum and above the mean lower low water datum] and generally fell in the lower third of this wetland zone based on elevation; 5) Converted to open water (that is, areas where the decade of initiation for coastal wetland drowning has passed and have been in the “converting to open water” class for at least 50 years); 6) Low-lying, developed (that is, areas that fall in elevation ranges for wetland classes [that is, regularly oceanic-flooded wetlands, regularly oceanic-flooded wetlands, and converting to open water], but are located within developed areas); 7) Low-lying, leveed (that is, areas that fall in elevation ranges for wetland classes [that is, regularly oceanic-flooded wetlands, regularly oceanic-flooded wetlands, and converting to open water], but are located within levees); and 8) Low-lying, developed and leveed (that is, areas that fall in elevation ranges for wetland classes [that is, regularly oceanic-flooded wetlands, regularly oceanic-flooded wetlands, and converting to open water], but are located within levees or developed areas). Incorporating soil elevation change processes into wetland transformation models can be complex because soil elevation change processes can vary over space and time. In the past decade, there has been growing consensus regarding critical sea-level rise rate thresholds for the onset of wetland drowning (Morris and others, 2016, Horton and others, 2018, Saintilan and others, 2020, Törnqvist and others, 2020, Buffington and others, 2021, Saintilan and others, 2022, Saintilan and others, 2023). Here, our products utilize information from an analysis of when and where sea-level rise rates could cross thresholds for initiating coastal wetland drowning across the conterminous United States. The thresholds included are 4 mm/year, 7 mm/year, and 10 mm/year (see discussion in Osland and others, 2024). For this approach, we determined the relative sea-level rise rate by decade for watersheds within the study area.  The decade that these rates exceeded one of these thresholds (that is, 4 mm/year, 7 mm/year, and 10 mm/year) marked the initiation of coastal wetland drowning. In other words, the 4 mm/year threshold indicates that wetland drowning would be initiated when the decadal sea-level rise rate exceeds 4 mm/year. Because wetland conversion to open water is not immediate once crossing this threshold, we left areas in that fell within “Converting to open water” class until 50 years after the threshold was surpassed. For example, if the decade the 4 mm/year threshold was crossed was 2020, then no wetlands would be moved to the “Converted to open water” class until 2070. For the 2070 map, areas in the “Converted to open water” class would include areas that were in the “Converting to open water” class in current wetland map (i.e., 50 years after the threshold was crossed). Similarly, for this threshold, areas in the “Converted to open water” class would be those that were “Converting to open water” class on and before 2030 (that is, 2030 and the current wetland map). For more information on the decades for when watershed-level drowning thresholds were passed, see the shapefile titled “Wetland_Drown_Years.shp.” Natural resource managers can utilize this information to explore potential scenarios related to the ability of current wetlands to adapt to sea-level rise via in situ vertical adjustment. For our study area, there was a high level of redundancy when the watershed-level drowning thresholds were passed, especially between maps for 4 mm/yr and 7 mm/yr. If users are interested in seeing where/when redundancy may occur, see the shapefile titled “Wetland_Drown_Years.shp.” This metadata file is for the datasets for the wetland current condition and wetland transformation by decade for sea-level rise scenario and coastal wetland drowning threshold.