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• Action Stage: The level which, when reached by a rising stream, represents the <br />level where the NWS or a customer/partner needs to take some type of <br />mitigation action in preparation for possible significant hydrologic activity. <br />• Minor Flood Stage: Minimal or no property damage, but possibly some public <br />threat. <br />• Moderate Flood Stage: Some inundation of structures and roads near the <br />stream. <br />• Major Flood Stage: Extensive inundation of structures and roads. Significant <br />evacuations of people and/or transfer of property to higher elevations. <br />The NWS has also indicated that reported flooding suggests the river levels used to <br />identify the Action Stage and Minor Flood Stage should be lowered. Recent hydraulic <br />modeling conducted by the Flood Control Zone District, which shows how water is <br />expected to move through the area during a flood, suggests that both the Action Stage and <br />Minor Flood Stage thresholds should be lowered. This hydraulic modeling has also been <br />used to identify potential moderate and major flood designations. The FCZD has <br />developed initial recommendations, which are shown in Exhibit 1. Exhibit 2 shows how <br />forecast and flood risk information is displayed by the NWS Northwest River Forecast <br />Center. <br />DISCUSSION: <br />These Easton Reach communities are our most at -risk flood communities. While river <br />forecasting is available at the EASW gage, this area currently lacks flood risk categories <br />for moderate and major flood stages. The lack of these flood designations risks <br />miscommunicating the potential impacts of upcoming flood events. <br />The flood risk categories are intended to serve as a communication tool for residents <br />living in these flood -prone communities and to help inform their flood response <br />decisions. If the flood risk categories are updated, FCZD funding for public outreach <br />could be used to inform Easton Reach area residents about the availability of forecast <br />information. We recommend coordinating with the Sheriff's Office on messaging for <br />outreach efforts. <br />FISCAL IMPACTS: <br />FCZD technical review, ongoing monitoring, and potential outreach efforts fall within <br />our annual budget for these items. <br />ATTACHMENTS: <br />Exhibit 1: Recommended river state height for NWS flood risk categories. <br />Exhibit 2: Example hydrographs at the Yakima River at Easton and Yakima River at <br />Umtanum with flood risk categories shown. <br />Page 2 of 4 <br />PUBLIC WORKS BOARD OF COUNTY CONMSSIONERS WORK SESSION STAFF REPORT <br />