Fire, Flooding, and Overtopping at the Santa Clara Pueblo Dams

On June 26, 2011, the Las Conchas fire began burning in northern New Mexico. At the time, it was the largest fire in New Mexico history, and it burned more than 150,000 acres of land. Within the Santa Clara Indian Reservation, the Las Conchas fire burned more than 16,500 acres (25 square miles) [3], a figure which amounts to nearly one-third of the size of the reservation. The reservation lands affected by the fire included a significant portion of Santa Clara Canyon, where a series of four significant-hazard dams owned by the Santa Clara Pueblo Tribe and administered by the Bureau of Indian Affairs (BIA) are located. Above the dams (Tschicoma, Nanaka, Weinpovi, and Pin Dee, listed in order from upstream to downstream and collectively referred to as the Santa Clara Pueblo Dams), the fire felled countless trees and scorched vegetation throughout the canyon, loosening and weakening the soils above the dams. The fire also led to the postponement of the site examination for the Santa Clara Pueblo Dams Comprehensive Dam Review (CDR), which had been scheduled to be conducted by Bureau of Reclamation (Reclamation) personnel on June 28 and 29, 2011. On August 3, 2011, the Las Conchas fire was finally 100 percent contained.
In July and August 2011, monsoon season rains caused significant debris flows in the canyon, and the reservoirs were filled with sediment and debris, reducing their storage capacity. The debris flows also plugged the outlet works at all four dams. On August 21, 2011, Nanaka, Weinpovi, and Pin Dee Dams were overtopped due to these heavy rains. The overtopping event caused extensive damage at the Santa Clara Pueblo Dams and their appurtenant structures, as well as in the channel downstream from the dams. (Although it appears that Tschicoma Dam did not overtop during this event, it did sustain some damage, as noted later in this paper.)