FLASH FLOODING HISTORY IN THE COLORADO NATIONAL MONUMENT

The physical environment of the Colorado National Monument - steep canyons, bare rock, semi-arid climate – creates conditions that are ideal for the production of flash floods. Intense summer monsoonal thunderstorms raining over the watersheds within and above the Colorado National Monument (CNM) can concentrate water rapidly in the steep canyons and dry washes creating swift and forceful floods. The CNM was established in 1911 to protect spectacular geologic features that were formed by the erosive power of water. Since human settlement of the region, flash floods emanating from these canyons have damaged houses, washed out roads, carried cars away, and threatened irrigation ditches. Between 1948 and 2003 at least 11 documented flash floods occurred that caused damage and/or flooding in the community bordering the CNM. The threat of future flash floods has not diminished and with recent intensified suburban development in this area, a thorough understanding of the flash flooding potential is essential. In addition, the morphology of the intermittent streams flowing through the CNM is determined by the stream flow and sediment entering the canyons. Future work monitoring and modeling of flash floods will increase understanding of the magnitude and frequency of stream flow responsible for the channel morphology.