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Vegetation in the study area varies according to elevation. In the valley areas below 8,000 feet not used for agriculture, vegetation is classified as northern desert shrub; that is, sagebrush, western wheatgrass, and winterfat, with an understory of various hardy grasses. Due to the poor ground cover in thi s region, snow tends to melt and run off rapidly. At the higher elevations, from approximately 8,000 feet to timberline, sub-alpine forests consisting of aspen, lodgepole pine, Douglas fir, and Engleman spruce are common. Runoff in this region is quite variable due to the mixture of rock outcrops and dense pine needle beds (Reference 3). The climate of Delta County is classified as generally semi-arid, with an abundance of sunshine, frequent wind, and low humidity. The prevailing direction of air movement to the region is from the west. On arrival, airmasses from the west are comparatively dry due to long travel over land and loss of moisture over mountain ranges. However, the primary sources of moisture are the Pacific Ocean and the Gulf of Mexico. Generally, airmasses from the Pacific Ocean dominate from October through April, while airmasses from the Gulf of Mexico dominate during late spring and summer. Historical climatologic information for the entire Delta County study area is very sparse. However, the mean temperatures in the City of Delta area range from approximately 26.40F in January to approximately 74.10F in July. Cooler temperatures prevail in higher mountain areas. The growing season usually extends upward to 140 days (Reference 4). Normal annual precipitation varies with elevation and ranges from approximately 7.9 inches at the Ci ty of Del ta to an estimated 40 inches at higher elevations in the study basins (Reference 4). Most of the annual precipitation in high elevation areas occurs as snow from December to April and, beginning in October, a deep snowpack accumulates. Snowmelt begins in late April and continues well into June or early July. General rain may occur over the study area, and convective-type cloudburst storms frequently occur in summer. The floodplains of all the streams studied are undeveloped, except for residential, commercial, industrial development within the communities along reaches. primarily and light the study 2.3 Principal Flood Problems Major flooding in the Delta County area has been the result of rapidly melting snow, sometimes augmented by general rain, during the period from May through July. Snowmelt flooding is characterized by moderate peak flows, large volume of runoff, long duration, and marked diurnal fluctuation of flow. Flooding from general rain is characterized by high peak flows and 6