DEVELOPMENT OF A METHOD TO ASSESS RIPARIAN VEGETATED BUFFER ZONES USING GIS AND REMOTE SENSING IN YOUNGS CREEK WATERSHED, JOHNSON COUNTY, INDIANA

Most bodies of water, both running and standing, have a floodplain or transitional riparian area. Often, the natural transition zone is altered through various land uses, and the protective nature of the riparian zone becomes ineffective or even detrimental to the health of the water body. Such problems have been encountered in the 130-square-mile Youngs Creek Watershed in Johnson County, Indiana. The specific water quality problems for the target watershed involve chemicals and excessive sediment from both agricultural and urban sources. The urban runoff increases channel erosion downstream and then deposits the eroded sediment into the lower watershed where it destroys habitat, decreases flow capacity, and eventually promotes flooding. These problems can be minimized by appropriately sized vegetated riparian buffers.

The purpose of the current project is to develop a method of riparian buffer zone evaluation using GIS and remote sensing to target areas with insufficient riparian protection. This technique allows efficient identification of degraded areas in the watershed. Our multi-phased approach involves using remote and on-site methods to categorize the reaches of stream within the watershed on the basis of landforms, soil types, and vegetation. Initially the buffer types are mapped on an aerial photographs map base. We are using Landsat ETM+ data to differentiate post-harvest management practices at the field scale in agricultural areas. Field surveys are used to ground truth our remote sensing methods. Using high resolution topographic data, we are conducting an assessment of the dimensions of the probable natural fluvial geomorphology of the stream, including sinuosity and gradient. In addition, the use of ancillary information contained in the Natural Resources Conservation Service county soil survey is used to provide detailed attributes to soil series polygons. Various maps are then derived from the soils maps such as geologic parent material, expected infiltration characteristics, and the spatial distribution of grain size. The appropriate buffer width is dependent on many variables, including land use, as well as local hydrological conditions. The local hydrology is a complex function of soil, topography, present vegetative cover, climate, and land use.