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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br /> <br /> <br />Chapter 4: Hazard Identification and Risk Assessment 129 <br />Flooding Source and <br />Location <br />Drainage Area <br />(square miles) <br />Discharge <br />(cubic feet/second) <br />10-Year 50-Year 100-Year 500-Year <br />West Fork Teanaway River <br />West Fork Teanaway River at <br />Mouth 39.3 1,300 1,640 1,780 2,080 <br />Upstream 19.2 790 1,000 1,080 1,260 <br />a Includes overflow from Yakima River, and Reecer, and Currier creeks. <br />b Combined values Reecer and Currier creeks. <br />c Includes overflow from Reecer Creek. <br /> <br />Flooding can be unexpected and leave a small window of time for evacuation, if it is required. The NWS <br />Pendleton, Oregon Forecast Office is responsible for issuing flood advisories in Kittitas County. Table 4- <br />65 outlines the flood advisories issued by the NWS as conditions warrant. <br />Table 4-65. NWS Flood Advisories <br />Type Definition <br />Flood Advisory <br />Issued when a flood event warrants notification but is less urgent than a warning <br />Advisories are issued for conditions that could cause a significant inconvenience, and if <br />caution is not exercised, could lead to situations that may threaten life and/or pro perty. <br />Flood Watch <br />Issued to indicate current or developing conditions that are favorable for flooding. The <br />occurrence is neither certain nor imminent. A watch is typically issued within several <br />hours to days ahead of the onset of possible flooding. In situations where a riv er or <br />stream is expected to be the main source of the flooding, forecast confidence may allow <br />for a Flood Watch to be issued several days in advance. <br />Flood Warning <br />Issued to inform the public of flooding that poses a serious threat to life and/or property. <br />A Flood Warning may be issued hours to days in advance of the onset of flooding based <br />on forecast conditions. Floods occurring along a river usually contain river stage (level) <br />forecasts. <br />Flash Flood Watch <br />Issued to indicate current or developing conditions that are favorable for flash flooding. <br />The occurrence is neither certain nor imminent. A watch is typically issued within several <br />hours to days ahead of the onset of possible flash flooding. <br />Flash Flood Warning <br />Issued to inform the public, emergency management and other cooperating agencies <br />that flash flooding is in progress, imminent, or highly likely. Flash Flood Warnings are <br />urgent messages as dangerous flooding can develop very rapidly, with a serious threat <br />to life and/or property. Flash Flood Warnings are usually issued minutes to hours in <br />advance of the onset of flooding. <br /> <br />NWS issues Flash Flood Warnings Impact-Based Warnings for events that occur within approximately <br />six (6) hours of heavy rainfall. The flash flood impact-based warnings fall into the three (3) categories <br />listed in Table 4-66.154F <br />154 <br />Table 4-66. NWS Flash Flood Impact Based Warnings <br />Type Definition <br />Base Used most of the time when flash flood impact is possible. <br /> <br />154 National Weather Service. (2019). Impact-Based Flash Flood Warning. Retrieved from <br />https://www.weather.gov/media/wrn/FFW-IBW-factsheet.pdf.