At Cherry Creek Dam, near Denver, Colo., a Dam Safety Modification Study is underway to consider and assess options for reducing the potential for life loss and property damage from detailed risks associated with the dam. The most significant safety concern at Cherry Creek Dam is the potential for overtopping during an extreme precipitation event. Although the chances for overtopping and/or failure are extraordinarily low, should high operational releases or a dam failure occur, a high urgency for action exists because of the potential for impacts to a large population that includes much of downtown Denver. For the more than 200,000 people living within this area, the dam reduces flooding risks for locations that would be prone to regular flooding.
Dams do not eliminate flooding, nor do they eliminate life loss, economic, or environmental damages from flood events. Should heavy rains occur, surface water runoff is stored in Cherry Creek Lake until the streams and rivers below the dam recede and can handle the release of stored water without life loss or property damage. In an extreme rain event, the reservoir may fill faster than releases can occur, the uncontrolled spillway may flow to protect the dam’s integrity even though streams and rivers may have already reached or exceeded their capacity. These water releases at high rates may cause downstream damages, and in an extreme event, the dam could overtop or a deficiency could cause a breach. To manage these risks, the U.S. Army Corps of Engineers has a safety program to routinely inspect and monitor its dams and implements short and long-term remedial actions when unacceptable risks are found.
Downstream residents must be aware of the potential consequences, which are increased by the large Denver-area population and warrants increased efforts on the part of USACE, local emergency management officials and residents to heighten public awareness of the potential flood risk associated with the dam. The potential for loss of life is highest immediately downstream of the dam along Cherry Creek and the South Platte River. Life loss potential also exists downstream of the spillway along Toll Gate Creek and Sand Creek. The counties of Denver, Arapahoe, and Adams have the highest potential for life loss. Additionally, USACE has implemented interim risk reduction measures such as increasing warning time by improving forecasting models and improving gages that monitor inflows of water into the dam during extreme rain events. Better downstream channel capacity inundation mapping has also been developed to aid emergency response agencies in flood evacuation efforts. To better control seepage pressure due to high reservoir elevations, additional relief wells have been installed at the downstream toe of the dam. These interim measures reduce risk to the public while potential long-term remedial measures are pursued. A Dam Safety Modification Study is currently underway to define in detail the risk associated with Cherry Creek Dam and assess options for further reducing these risks associated with the dam.
The annual flood damage reduction benefits provided by the project for the time period of 1965 to 2013 are estimated to be $25,000,000. Recreation resources at the project include over 800 acres of water surrounded by nearly 4,000 acres of land. Estimated annual project visitation is nearly 4,000,000.