Marsh Types of the Texas Coast

Detailed information on the extent and distribution of marsh vegetation zones throughout the Texas coast has been historically unavailable.  To address this data gap, the USGS NWRC in collaboration with others, produced a seamless and standardized classification of marsh vegetation types indicative of salinity zones (i.e., fresh, intermediate, brackish, and saline) along the Texas coast from Corpus Christi Bay to the Sabine River.  Decision tree analyses were used to classify marsh types from a combination of 1,000 reference points, multitemporal satellite imagery from 2009–2011, a lidar-based  bare-Earth digital elevation model, contemporary land cover classifications, and other spatial variables believed to influence marsh vegetation zonation.    An accuracy assessment was conducted for the classification.  The classification performed best for saline marsh but showed a lesser ability to discriminate intermediate marsh.  Because of confusion in intermediate and brackish marsh classes, an alternative classification containing only three marsh types was created in which intermediate and brackish marshes were combined into a single class.  The average user’s accuracy (measures error of commission) for marshes within the four-marsh-type and three-marsh-type classifications was 65.4% and 75.6%, respectively, whereas average producer’s accuracy (measures error of omission) was 56.7% and 65.1%, respectively. This project demonstrated the effectiveness of a consistent and repeatable methodology for delineating salinity zones of Texas coastal marshes at a landscape scale.  This classification will enable State agencies and conservation partnerships (e.g., Gulf Coast Prairie Landscape Conservation Cooperative and the Gulf Coast Joint Venture) to develop and/or refine conservation plans for priority coastal resources. These data have been published as a USGS Scientific Investigations Report (http://pubs.usgs.gov/sir/2014/5110/).