Sedimentation Research Needs in Semiarid Regions

Sedimentation problems to semiarid areas of the southwestern United States are especially acute as they relate to sparse vegetative cover of wild rangelands, severely intense thunderstorms, and flash floods. Sediment loads and the channel stability of ephemeral streams are highly inter-related with their flow regimes, and vary widely with both watershed and climatic variables. Present data are inadequate for predictions of erosion and sediment deposition damage, and sediment storage requirement of reservoirs, for engineering planning and design. The needs for such data are increasing rapidly with the population explosion, urban development, building of expensive highway systems, and the long-range outlook for vastly increased development of water supplies throughout the Southwest in the last decade. The need is for more intensive research relating the basic processes of detachment, entrainment, transport, deposition, and consolidation of fluvial sediments to properties of the materials, quantitative watershed geomorphic parameters, and the overall hydrology of the stream systems. Also, measurement techniques need intensive effort for improvement In several phases if sedimentation research is to advance from its present highly imperical status to that of a theoretical science.