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<br />IV. FLOOD HAZARD AWARENESS <br /> <br />A. STORM EVENTS <br />The summer storm that produced flash flooding in the Buffalo Creek area was a typical convective <br />type cloudburst event. This type of event is not uncommon along the foothills and plains in eastern <br />Colorado. Storms like this form quickly and can produce large amounts of rainfall, hail, and severe <br />weather conditions within a short amount of time. <br /> <br />At this time, only preliminary information is available describing the particular storm over Buffalo <br />Creek. The information is based on field analyses, rain gage information, and interviews with <br />witnesses and local residents. The most intense rainfall amounts are estimated to be from 2 inches <br />to 4 inches within 30 to 90 minutes. The storm may have covered an area between 10 and 30 <br />square miles. To provide a point of reference, the lOO-vear, I-hour precipitation depth for southern <br />Jefferson County is reported to be about 2.1 inches according to the Jefferson County Storm <br />Drainage Design and Criteria Manual. <br /> <br />It is important to note that the flood peaks on Sand Draw, Spring Gulch, Buffalo Creek, and other <br />nearby tributaries occurred within less than one hour from the start of the heavy rainfall. Flow <br />velocities in some streams were at least 15 to 20 feet per second. This situation, known as flash <br />flooding, is extremely dangerous. Residents, recreationists, and visitors should be aware of and <br />prepared for future flash flooding that could potentially occur in the area. Property damage and loss <br />of life is always a possibility during flash flooding. The power of a flash flood event should not be <br />underestimated! <br /> <br />B. WATERSHED RECOVERY <br />The natural recovery of the burned areas in the Buffalo Creek vicinity could be a long process. <br />Fortunately, with the aggressive reclamation actions by the V.S. Forest Service and the Colorado <br />State Forest Service, the initial stages of the recovery should be enhanced and accelerated. The <br />hydrologic response of the burned watersheds will depend on the level of vegetative and soil <br />surface recovery. Following are some key phases to the recovery process: <br /> <br />. Break.up of hydrophobic (water repellent) soils <br />. Recovery of native grasses, forbs, and shrubs <br />. Recovery of native trees <br />. Recovery of humus layer (organic layer at soil surface) <br /> <br />The effects of an intense fire on the watershed's soil structure and hydrology can be significant. <br />The following key points about the effects of fire on soil and hydrology were extracted from V.S, <br />Forest Service publications. <br /> <br />. For arid areas of the V,S" vegetative regrowth after a severe burning can be very slow, <br />. Coarse textured soils are more likely to become higWy water repellent than fine clay soils. <br />. Lodgepole and Ponderosa Pine forests have displayed high water repellency after burning, <br /> <br />12 <br />