Tuesday, 8 November 2005 - 8:45 AM
188-2

Using Digital Elevations and Models to Enhance Stream Network Maps in Virginia.

John M. Galbraith, Patricia Donovan, Alexis Sandy, and Eva Pantaleoni. Virginia Tech, Dept. of Crop & Soil Env. Sci., 239 Smyth Hall (0404), Blacksburg, VA 24061

Agencies are required to use highly-detailed maps when estimating the impacts of human activities and environmental inputs on water quality and quantity. First-order streams are also called headwaters and are often the site of wetlands and springs that supply and filter waters coming from recharge areas. The location of first-order streams on digital data sets is inconsistent, yet these streams may comprise the greatest proportion of the total stream system length and are often the sites of easiest alteration and greatest impact by humans. The purpose of this study is to compare the stream network generated by modeling the wetness index from digital elevation model data and comparing those flow networks to the hydrology on 1:24,000 digital topographic maps in the mountains of Virginia. The steady state wetness index is a derived from both the slope and the upstream catchment area per unit width perpendicular to the flow direction. The scanned 1:24,000 topographic maps or National Hydrography Data will be converted into raster data sets and will be located concordant to the wetness index data. The correspondence and goodness of fit between data sets will be calculated. Wetness index pixels that are not highly correlated with streams on the topographic map will be deleted. The stream order characteristics of each data set from benchmark locations will be calculated and compared. Field validation on occurrence of first-order streams will be conducted on a fraction of the study area. The potential use of each data source and best method to digitally-identify first-order streams will be demonstrated and discussed.

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