1. Via Department of Civil and Environmental Engineering, 418 Durham Hall, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S. Geological Survey, 4821 Quail Crest Place, Lawrence, Kansas 66049, Department of Soil & Crop Sciences, Colorado State University, Fort Collins, Colorado 80523, and Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, Colorado 80523