Study of Ouray — a small mountain city with a long history of destructive debris flows. Includes description of past events, local geology, hydrology, damage incurred, mitigation attempts and costs, and map of hazard zones. 69 pages. 38 figures. 1 table. 1 plate (1:24,000). Digital PDF download. SP-30D
From the Introduction:
Debris flows are among the most destructive geologic processes that occur in mountainous areas. While modern land-use planning should prevent construction in areas subject to debris-flow hazard, debris fans have historically been enticing places to build. They often provide the only apparently “suitable” construction sites between areas of steep valley sides and riverine flooding. Most of Colorado’s mountain towns were founded during the mining-boom era from 1860 to 1900 and were built without the benefits of land-use planning or much understanding of the debris-flow process. The existence of communities in geologically hazardous areas presents a potential threat to the inhabitants, as well as a financial burden on local and state governments.
Ouray is a small mountain town that has periodically experienced damaging debris flows since it was founded in 1875. Although there have been no recorded human fatalities within the city itself, recurring damages to buildings, roads, and water and sewer systems and attempts at structural control have been very costly.