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 (ver. 2.0, August 2025)

As sea levels rise, wetlands exposed to oceanic water can adapt to changing conditions through vertical development (i.e., 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 transformation 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 and upriver classes; 2) Irregularly oceanic-flooded wetlands (that is, wetlands that are flooded by oceanic water less frequently than daily); 3) Regularly oceanic-flooded wetlands (that is, wetlands that are flooded by oceanic water daily and generally fall in the upper two-thirds of this wetland zone based on elevation); 4) Wetlands 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 fall in the lower third of this wetland zone based on elevation); 5) Wetlands converted to open water (that is, former wetlands that were flooded by oceanic water daily [that is, below the mean high water datum and above the mean lower low water datum] and generally fall in the lower third of this wetland zone based on elevation); 6) Low-lying, developed; 7) Low-lying, leveed; and 8) Low-lying, developed and leveed. Incorporating accretion rates into wetland transformation models can be complex because accretion can vary over space and time. Instead, these products utilize information from a synthesis on decadal sea-level rise rate thresholds thought to lead to the potential initiation of coastal wetland drowning, specifically 4 mm/year, 7 mm/year, and 10 mm/year (Osland and others, 2024). For this approach, we determined the relative sea-level rise rate by decade for watersheds within the study area and 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 wetlands will be able to adapt, to a degree, to sea-level rise through vertical movement, 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 2020, then no wetlands would be moved to the “Converted to open water” class until 2070. At that point, areas in the “Converted to open water” class would include areas that were in the “Converting to open water” class in the current wetland map. 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 optimism on the ability of current wetlands to adapt to sea-level rise via in situ vertical adjustment (for example, results for the 4 mm/year thresholds are less optimistic than the results for the 10 mm/year thresholds). 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.”

Tags: aransas, coastal-ecosystem, corpus-christi, east-galveston-bay, east-matagorda-bay, elevation, environment, geoscientificinformation, gulf-of-america, matagorda, remote-sensing, sabine, san-antonio, texas, united-states, usgs-66ead158d34e0606a9dba9a2, west-galveston-bay, wetland-ecosystems
Organization: Department of the Interior