Runoff and soil loss data were collected for four rainfall seasons from six natural runoff plots situated on a 6% uniform slope area in the low rainfall zone of northern Iraq. There were three plots 30 m long and three plots 10 m long. Rainfall at the site was found to be highly variable. Individual storms were classified as severe and normal storms. Severe storms are the least frequent but account for the bulk of seasonal runoff and soil loss. Runoff ratio significantly decreased in dry seasons. Seasonal soil loss was generally low due mainly to the gentle land slope and the dominantly low intensity rain. Runoff and soil loss from single storm events were simulated using the concepts of stream power and the conservation of mass and energy. Observed and simulated runoff and soil loss agreed reasonably well. Observed runoff and soil loss records were also used to test the validity of the USDA-Soil Conservation Service (SCS) curve number method and the universal soil loss equation in the region. It was concluded that these two prediction methods need modification to suit rainfall and soil loss patterns in the region. Runoff and soil loss prediction on a single storm basis is emphasized.
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