Washoe County Truckee River Flood Response Plan (FRP) – US Army Corps of Engineers
Reno and Sparks, Nevada

In January 1997 the Cities of Reno and Sparks, Nevada experienced a serious flood that produced millions of dollars in structural damage in downtown Reno and closed the Reno airport for two days.

After the flood, the Corps of Engineers embarked on the development of flood mitigation measures that included both structural and non-structural. Structural measures included an enhanced flood detection network (FDN) along the Truckee River and its tributaries as well as flood proofing portions of the watercourse. The FDN included automated stream gauges, rain gauges and automated weather stations within the important basins and sub-basins. Software was put in place in the County and City emergency response agencies, National Weather Service (NWS) Forecast Office in Reno, Nevada and the NWS River Forecast Center in Sacramento, California to display the FDN information.

A detailed agency inventory and interview process was performed and set the stage for a detailed tabletop flood exercise to obtain additional information on the agencies for the development of the FRP.

HDR meteorologists produced an FRP that incorporates both the existing FDN and a Flood Threat Recognition System (FTRS) that recognizes the flood threat, assesses the threat and then notifies appropriate agencies of the flood threat.

The FRP identifies the proactive responses needed by each agency and organizes the information used by decision-makers to assist in effective use of response resources.

The FTRS uses a combination of prediction and detection criteria that HDR developed, to recognize a flood threat and prompt levels of preparedness that are associated with a time period before flooding is expected. Figure 1 shows the FTRS criteria, the preparedness level that this criteria prompts and the associated proactive agency actions.

Detailed floodplain mapping, depicting predictive inundation, has been incorporated into the FRP to help decision makers visualize the potential flood. A Flood Severity Chart was developed by HDR that contains information on flood inundation, water depths, critical facilities being affected and the associated stage and flow values.

HDR designed the FRP so that it can be embodied within and make use of the County’s GIS system in the future allowing for such things as street level flood inundation mapping, and GIS based FTR tools.