干旱区生态环境知识资源中心

The assessment of flash flood potential of wadi (dry river) systems in arid lands is often difficult because of the lack of sufficiently long rainfall and discharge records of the infrequent and spatially variable rainfall events. Characterization of active wadi systems by remote sensing may offer an alternative solution. A methodology is presented to characterize the channel infill of wadi systems based on the soil composition, and the geomorphic and geologic properties of drainage basins. Spectral mixture modeling is performed on a Landsat TM image to identify the source material (endmembers) and source upland area of the alluvial infill. Endmembers are determined by two methods: (1) identifying pure image pixels, and (2) using spectral libraries representing main rock units of the drainage basin. Both methods are evaluated in terms of their ability to establish the relative contribution of upland source rocks to the overall alluvium composition in the lowland. The identification of wadi systems that are presently most active (high stream-power values) and efficient in transporting sediments to the basin outlet may enable identification of areas prone to flash floods.