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<br />002788 <br /> <br />might take several months to clear, costing the state as much as 600 million <br />dollars. A landslide dam could back up water into Minturn and West Vail. <br />Subsequent flooding from failure of the landslide dam would seriously endanger <br />such towns as Avon, Edwards, Eagle, Dotsero, and Glenwood Springs, as well as <br />downstream communities as far away as Grand Junction. <br /> <br />The city of Glenwood Springs is almost entirely encircled by small basins that <br />produce debris flows which endanger numerous residences, a hospital, <br />educational facilities, and commercial development. The city of Grand Junction <br />has also felt the impact of landsliding in its Lamplite Park Subdivision, <br />where several homes have already been condemned and evacuated. These two <br />areas are included as case studies no. 2 and no. 3. <br /> <br />Landsliding in Colorado has intensified as a result of increased annual <br />precipitation over the last five years. Although landsliding has been <br />occurring since mountains were formed in Colorado's geologic past, the recent <br />cycles of increased precipitation and expanding population growth have created <br />an increased likelihood of disaster. <br /> <br />Landsliding throughout the United States has already become extremely costly - <br />$1 to $2 billion dollars and 25 to 50 deaths each year (NRC, 1985). Despite a <br />growing repertoire of landslide mitigation strategies in the engineering and <br />planning disciplines, losses from landslides across the nation are continuing <br />to increase. As in Colorado, this is largely due to expanding residential and <br />commercial development in areas of steeply sloping terrain that are most <br />susceptible to landsliding (NRC, 1985). <br /> <br />Other hazards related to landsliding: Flooding in Colorado has for many years <br />been the state's most frequent and costly hazard. Landsliding is closely <br />allied to flooding in that both are related to precipitation, runoff, and <br />ground saturation. The increasing exposure, created by ongoing development, <br />to hazards that have existed over millions of years leads to modern disasters. <br /> <br />Most of the mountainous areas of Colorado that are most vulnerable to <br />landslides have also experienced a moderate level of seismicity in historic <br />times. The coincidence of these hazards has the potential, under certain <br />conditions, of increasing the risk of serious damage to a level considerably <br />higher than if,they were not interrelated. <br /> <br />- 2 - <br />