Interdigitation of Estuarine Tidal Marsh Types in GCPO LCC (LA, MS, AL) [DRAFT]

Prior to 2014, coastal estuarine marsh types had to be inferred from local marsh mapping projects, or from water chemistry modifiers included in National Wetlands Inventory when available.  In many cases, determination of palustrine vs. estuarine was the only available information across a large spatial scale.  The USGS marsh type delineation project (MTDP) was developed to provide a standardized delineation of marsh vegetation types per three and four salinity zones along the northern Gulf of Mexico following the Chabreck et al. (1968) classification (see Table TM.1) (Enwright et al. 2014).  Thus far, the marsh type delineation project has delineated fresh, intermediate, brackish, and saline marsh types, in addition to water and non-marsh classes from Corpus Christi Bay, Texas to Mobile Bay, Alabama.  The project uses 2009-2011 Landsat TM and SPOT 4 and 5 satellite imagery, existing land cover classifications, calculated vegetation and water indices, lidar-derived elevation data, and topographic and distance indexes to produce a step-wise decision tree analysis in See5 and other software programs in combination with 2011-2012 ground referenced observations. 
We used the USGS MTDP layer to assess composition of saline, brackish, and intermediate marsh as a surrogate for interdigitation in delineated marsh patches in the Louisiana, Mississippi and Alabama portions of the GCPO LCC Gulf Coast subgeography.  We first ran a Zonal Statistics analysis in ArcGIS to calculate the proportion of saline, brackish, and intermediate marsh within each patch.  Then calculated measures of interdigitation of the three marsh types, or patch richness, within each patch, with a patch richness value of three indicating presence of saline, brackish, and intermediate marsh within the patch.