Sweetwater Marsh Restoration Project
Habitat Mapping using GIS, GPS and Remote Sensing
Restoration of coastal wetlands at Sweetwater Marsh National Wildlife Refuge, adjacent to San Diego Bay, required monitoring and evaluation to determine whether suitable habitat for the endangered light-footed clapper rail had been established. Clapper rail habitat is defined by a specific mixture of lower, middle, and upper marsh vegetation types. In order to map the marsh types, digital multispectral image data with a spatial resolution of 0.75 meters were acquired with the Airborne Data Acquisition and Registration (ADAR) 5500 system. In addition, digital elevation data and vegetation samples were collected with a kinematic Global Positioning System (GPS) survey, providing positional accuracies within 5 cm and measurement accuracies within 1 cm. The GPS survey data were used to develop ecological models defining the relationship between elevation and marsh vegetation types. The elevation point data from the survey were interpolated using kriging to generate Digital Elevation Models (DEMs). The image data, DEMs and ecological models were integrated to develop maps defining the extent of the marsh types so that the adequacy of clapper rail habitat and the success of the restoration efforts could be determined.