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, I I I 1-5 Within the study reaches, the Lake Fork has an average gradient of 0.6% and an average channel width of 60 feet_ Normal water depths are 2.5 feet. Henson Creek, within its study reach, has an average gradient of 1.2%, averaQe width of 50 feet anc average depth of 2 feet (during normal flows). Stream sub-strate consis:s of large boulders, cobbles and bedrock. Streamside vegetation consists of cottonwoods, willows and similar brush along both streams. Obstructions to floodflows within the study reach include both natural obstructions such as vegetation growth, fallen trees, ice jams, etc. and man-made obstructions such as bridges, buildings, fences and roadways. These obstructions have a tendency to increase flood elevations upstream of the obstructions and increase velocity downstream of the obstruction. The stream valley above the Lake Fork study reach is essentially similar to the study reach description (except it has a narrower flood plain). Lake San Cristobal, a natural lake approximately 3.5 miles above Lake City, has a dampening effect on potential floods such as those occurring from high intensity, short duration rainfall. For long duration spring snowmelt and combination rainfall, however, the effect of the lake on peak floodflows is minimal. The stream valley above the Henson Creek study reach is very narrow and steep. Trees and brush grow out over the channel in many areas along this tight valley. High waters could carry great amounts of debris through the study reach and accentuate the flood elevations. The historical use of the floodplain has been for range, wildlife and resort activities. Land adjacent to the streams is privately owned. These areas have good plant cover and support meadow vegetation, willows and cottonwood. Small areas within the floodplain are flooded annually and support little or no vegetation. The growth of Lake City in recentyears.has forced greater development in the flood plain. With this increased encroachment of development in the flood plain, the flood hazard to the community is increased and will continue in the future unless adequate measures are adopted to keep the development outside the flood hazard areas.