MAPPING SUBMERGED AND EMERGENT COASTAL HABITATS IN AN URBANIZED TIDAL CREEK WATERSHEDS

In general, tidal creeks are coastal environments characterized by having low freshwater input, low-gradient, marine and brackish salinities, and subtidal, intertidal, and supratidal habitats. They have largely varying sizes but are hydrologically dominated by tide cycles regardless of the environment being micro-, meso-, or macro-tidal. In North Carolina, as coastal population has grown, there is concern that urbanization leads to detrimental changes in the tidal creek habitats such as degraded oyster beds. Therefore, the purpose for this project is to investigate the mapping capabilities of new satellites in small tidal creeks. A variety of data have been gathered including historical aerial photography, satellite imagery from Landsat 8 and DigitalGlobe, local government GIS data, LiDAR, and field work data. An field effort via boat and kayakvisited over 200 locations where the habitat type, survey-grade GPS coordinate, pictures, and notes were recorded. These data were used in the image classification and accuracy assessment. Each sampling site on an oyster bed was classified as high, medium or low density and these data were used to create an oyster reef quality index. A variety of results have been obtained: supervised classification of the WorldView-2 imagery was more accurate than unsupervised; field work data greatly improved the ability to map submerged and emergent coastal habitats; and algorithms for calculating water depth from the WordView-2 imagery provided information for mapping the benthic habitats. The high spatial resolution of the WorldView-2 imagery (1.85 multispectral and 0.46m panchromatic) resulted in the ability to map small features within the study area and could distinguish between salt marsh species such as cord grass (Spartina alterniflora) and black needle rush (Juncas roemarianus). The combination of high spatial and spectral imagery, good elevation LiDAR data, extensive field work, and robust image processing and GIS software has resulted in tidal creek maps that can be compared with terrestrial land cover maps. The next stage in the project is to compare habitat changes within the creek to upland changes to see if there are spatial and temporal patterns.