Development of a Comprehensive Habitat Map for the Mission Aransas NERR Using the NERRS Habitat Classification Scheme: Matagorda Island, Texas

The National Estuarine Research Reserve System (NERRS) developed a new hierarchical classification scheme to standardize mapping techniques and terminology throughout all its reserves. The Mission-Aransas National Estuarine Research Reserve (NERR) obtained habitat information from various sources and reclassifed habitats according to the NERRS scheme using a geographic information system (GIS). Mapping the Mission-Aransas NERR manually at a high spatial resolution was desired, but proved challenging because of its considerable size (185,708 acres) and limited accessibility to privately-owned land areas. Existing digital habitat information was identified and obtained from partner agencies in an effort to create a comprehensive habitat map of the Mission-Aransas Estuary and the adjacent watersheds. Geospatial habitat information available within the Mission-Aransas Estuary and the adjacent watersheds were identified and assessed for appropriateness of this project by the following attributes: scale, resolution, habitats identified, location, accuracy, accessibility, and temporal relevance. The University of Texas at Austin Bureau of Economic Geology (UT BEG) had a high–resolution habitat dataset of the wetlands on Texas barrier islands. A portion of this data on Matagorda Island is within the Mission-Aransas NERR boundary and was used as a case study for reclassifying data to the NERRS classification scheme. The Matagorda Island data were provided to the Mission-Aransas NERR in vector (polygon) format, and this document outlines the procedures used to reclassify this type of data. However, vector data is not the only type of data available, and an additional method of reclassification using a raster format was also explored. This document demonstrates the process of vector and raster data reclassification for geospatial habitat information. The Matagorda Island wetlands data were originally classified using the Cowardin classification scheme, which implemented codes describing specific habitats to the modifier level (Cowardin et al.1979). Reclassification of this data from a Cowardin scheme to the NERRS scheme required the data be organized into a hierarchical database structure. A look-up table was created to compare the two classification schemes. Reclassification of the vector data required the application of the join-relationship tool supplied within the GIS environment. Reclassification of the raster data required the application of the reclassification tool supplied within the GIS environment. One of the major differences in the NERR coding system to the Cowardin classification is that upland habitat is described in great detail. Since the Matagorda Island data only contained wetland habitat information, several NERR codes were not correlated to this dataset. This report documents the methods, challenges, and recommendations of reclassifying existing data to the NERRS classification scheme. It represents the first phase in the creation of a comprehensive high resolution habitat map. Future work will incorporate additional datasets for complete coverage of the Mission- Aransas NERR habitat areas