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'Natural' Streams Were Shaped by Dams (2 of 2)

Caption: High-resolution topographic data from airborne laser swath-mapping (LIDAR) is a powerful new tool for studying the Earth's surface. Color-relief hillshade images for a southeastern Pennsylvania landscape provide information regarding sedimentation in valley bottoms upstream of low-head milldams. Changes in altitude along stream corridors coincide with locations of early American milldam remnants and illustrate backwater effects at tributary junctions. The elevation of the stream bed decreases from top (dark purple) to bottom (light purple). This image relates to an article that appeared in the Jan. 18, 2008 issue of the journal Science, published by AAAS. The study, by Drs. Robert Walter and Dorothy J. Merritts at Franklin and Marshall College in Lancaster, Penn., was titled "Natural Streams and the Legacy of Water-Powered Mills."

Credit: LIDAR data and preliminary processing courtesy of the United States Geological Survey. Image analysis and generation by Michael Rahnis, Department of Earth and Environment, Franklin and Marshall College

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