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Four general soil associations predominate in the study watershed. In the lower basin, the Billing-Ghristianburg association is made up of deep, nearly level and gently sloping, fine to moderately fine textured soils on alluvial fans, flood plains, and terraces. The Chipeta persayo association is constituted of shallow, nearly level to hilly fine to moderately fine textured soils derived from shale or mudstone. The Bostwick-Cerro association is found in the upper basin areas. It is composed of deep, gently sloping, moder- ately fine textured soils on alluvial fans and valley side slopes. The rock outcrop-Travessilla association is composed of bare rock outcrop and shallow, rolling to steep moderately coarse textured soils found on hills, ridges, and sides of mesas. Along much of the major drainages, the vegetative cover consists of extremely dense cedar, juniper forest, and sagebrush, with accompanying heavy debris. The land in the upper basin is covered with moderate to dense growths of brush with a native grass under- story. The remaining areas in the lower basin are primarily the "badlands" of steeper slopes with minimal ground cover. The vege- tation that does exist is composed of various native grasses and forbs, with occasional sage. The vegetation in the urbanized areas is composed mainly of trees and lawns (which tend to reduce runoff due to the usual minimal slope and the higher water absorption). Th~ widely varied topography of the region - mountain ranges, high plateaus and mesas, and the comparatively high Uncompahgre Valley - creates distinct and varied climatic conditions. Low humidity and mild year-round climatic conditions generally prevail because of the protection afforded by surrounding high mountain peaks, which tend to attract moisture from passing storms but also protect the valley from high-velocity winds. However, temperatures often drop below freezing in winter and rise to over 900F in summer. Average annual mean temperatures range from 350F to 640F. Normal annual rainfall averages approximately 9 inches. Rain Occurs throughout the year, with the smallest amount in June and the largest amount in August. Average annual snowfall is approximately 30 inches. In the high headwater regions, normal annual precipita- tion averages approximately 45 inches and occurs mostly as snow that usually accumulates as a snowpack. The flood plains of all the streams studied are primarily urbanized with residential, commercial, and light industrial development. 2.3 Principal Flood Problems Floods in the study area generally result from rapid melting of the mountain snowpack from approximately the middle of May through early July, and from general rainstorms that normally occur from 5