Mile High Flood District’s Approach to Early Flood Threat Recognition and Warning

The Mile High Flood District (MHFD) is a special district that serves the seven-county greater Denver/Boulder metro area in Colorado with a comprehensive work program that includes early detection and notification of flood threats. MHFD (formerly known as the Urban Drainage and Flood Control District or UDFCD) has provided these services for the past 42 years through partnerships with the National Weather Service (NWS), emergency management agencies, first responders, local news outlets, universities, research organizations, and others. In addition, local flood warning programs depend on the FEMA mapping process and Risk Mapping Assessment and Planning (Risk MAP) products to achieve desired outcomes.

MHFD’s flood warning services have vastly evolved over the past four decades as technological advances continue for emergency communications, real-time data acquisition and processing, information sharing, and automation. The early flood detection aspect relies on both human and automated processes, starting with a forecast of potential threats using the services of a private-sector meteorologist that feeds information to the public warning and forecast services of the NWS.

This early prediction component is commonly known as the Flash Flood Prediction Program, or F2P2. From its launch in 1969, the local flood control department prioritized the need for local flood warning enhancements. The UDFCD determined after the 1976 Big Thompson Canyon Flash Flood that more serious actions were needed and introduced the F2P2 three years later.

In the years that followed, lessons from the Big Thompson flood and many others incentivized improvement in services. These events increased flood risk awareness and motivated local governments to be more prepared to effectively manage flood risks. Combined with better weather forecasting, the network of rain and stream gauges expanded to provide continuous monitoring of threatening weather and flood conditions. In addition, radar-based precipitation products evolved along with the use of real-time hydrologic models. Automated threat notification through text, email and social media have become common. The goal is for individuals to take actions to save lives and reduce property damage.

• Basin-specific warning plans were developed for the highest risk watersheds. Those plans were incorporated into local emergency response plans by local governments, emergency action plans for dam safety, and standard flood operating procedures for the MHFD, NWS, F2P2 meteorologist, and many local agencies.
• MHFD has maintained a Flood Emergency Support Plan (formerly known as a Flood Disaster & Mitigation Plan) since the inception of the F2P2 in 1979. The plan is reviewed annually and periodically revised by the MHFD Board of Directors.
• MHFD and their respective local governments routinely conduct flood exercises and program reviews.
• Communities have become aware of their respective flood risks and provide community education programs for the public.

• Communities become safer by recognizing potential flood threats and taking protective actions before flooding. Emergency managers, first responders and citizens are critical to this process. In addition to saving lives, early flood threat recognition provides more time to avoid or greatly reduce costly damages to infrastructure and property.
• Local governments become vested in the entire flood warning process. Close relationships with the NWS and MHFD are more firmly established. Local public works and public safety agencies have new opportunities to collaborate and prepare for future flood emergencies and disasters. This process also allows elected officials and local government administrators to own a system they created and help maintain.
• Education, outreach and communication with the public occurs following impactful storms and floods. The wide availability of real-time flood data from MHFD helps build relationships with local news organizations. MHFD and its partner agencies become trusted subject matter experts on floods and flood safety.
• For regional agencies, geographical boundaries are opportunities to increase cooperation between local governments that share common flood risks. Regional flood warning and early flood threat detection become an effective tool for developing these close working relationships.
• Local flood warning programs depend on FEMA’s mapping process and Risk MAP products to achieve desired outcomes; and the National Flood Insurance Program is supported by increased local knowledge about flood risks and the many effective ways to manage those risks.
• Flood insurance cost savings are realized through the FEMA Community Rating System program, a voluntary incentive program for communities.

• Local flood warning programs enable a better understanding of extreme flood probabilities. Knowledge about a region’s flood history helps people personalize their flood risks.
• Automated rain and stream gauging networks are helpful to recognize imminent flood threats. Other remote sensing techniques using radar can result in greater lead times for responding to flash flood threats.
• Real-time hydrologic models are helpful tools for predicting impacts, but should not be heavily relied upon for smaller watersheds that are highly prone to flash floods. Impact forecasting meaningful to emergency management is a worthwhile undertaking.