Rain gauges, postcards part of Emergency Flood Notification Process
Amy Hendershot, Resource Conservationist
WENATCHEE, WA (June 25, 2013)—Officials from several government agencies worked together to install 10 Automated Local Evaluation in Real Time (ALERT) stations on lands managed by the U.S. Forest Service (USFS) and Washington State Department of Natural Resources (DNR) that wildfires burned last year.
A September 8, 2012, lightning storm with approximately 4,000 strikes ignited more than 100 fires across 4.2-million-acres in the Okanogan and Wenatchee National Forests. Emergency management officials are now concerned a short-duration deluge of rainfall in burned areas could cause significant downstream runoff this summer and during the next three years.
This network of ALERT stations within or adjacent to the burned areas provides site-specific precipitation data that will be used for flood and mudslide forecasting for communities downstream from these areas.
Through an interagency effort, Chelan County Public Works Department mailed 23,000 postcards to residents who might be affected by floods or mudslides. The postcards include information on the ALERT system and a website with details: www.co.chelan.wa.us/pw/rain_gage.htm.
Working with USDA’s Natural Resources Conservation Service’s (NRCS) Emergency Watershed Protection Program (EWP) and the Cascadia Conservation District, the Chelan County Public Works and Natural Resource Departments were able to purchase rain gauges, which were installed and will be maintained by the U.S. Geological Survey (USGS). The rain gauges are located upstream from No. 1 and No. 2 Canyons near Wenatchee, Mission Creek near Cashmere, Oklahoma Gulch near Entiat, and First Creek near Lake Chelan’s south shore. Site selection was based on location of communities, historic flooding, and burn severity.
Rainfall amounts exceeding one-tenth of an inch in 10 minutes initiate rapid data collection and monitoring of rainfall. Officials say this rain intensity is similar to a downpour heavy enough to cause a driver to pull over when windshield wipers cannot keep up with the rain. Severe local thunderstorms in summer months can cause concern. Each rain gauge will transmit data hourly via satellite to a USGS database monitored by the National Weather Service (NWS). Data will be transmitted at shorter intervals during heavy rainstorms.
The NWS may issue weather advisories, watches, and/or warnings based on the data from the rain gauges. The public can track conditions through National Oceanic Atmospheric Agency (NOAA) weather radio, local weather forecasts or NWS Facebook and Twitter updates.
Emergency management officials advise the public not to rely solely on warnings from these agencies. They recommend people remain vigilant when heavy rain occurs in burned areas or locations downstream from burned areas.
Hearing or seeing rushing water or a large volume of debris in mudslides might be the only indication of a hazardous situation. People should quickly move to higher ground away from rivers, streams, canyon bottoms and storm drains when they suspect a flood or mudslide is pending.
A thunderstorm in July 2010 caused massive flooding, road closures and power failures when rain overwhelmed storm drains in Wenatchee and East Wenatchee. The storm did not occur in burned areas, yet caused Highway 97A closures, and flooding in No. 1 and No. 2 Canyons. The burned areas from last summer and fall, which have only begun recovering vegetation lost to the fires, include soils that are less absorbent and at more risk of flash flooding or debris flows.
Flash flood preparedness includes clearing nearby culverts and storm drains of debris, and keeping food, water and other emergency items on hand. The American Red Cross provides more tips online: www.redcross.org/prepare/disaster/flood.
More preparedness and flood watch information can be found at the interagency Central Washington Fire Recovery website: http://centralwashingtonfirerecovery.info.
In addition to installation of rain gauges, the Chelan County Public Works and Natural Resource Departments, NRCS, and USFS completed numerous treatments to reduce threats to life and property until burned vegetation regrows and provides improved slope stability.
These projects included installation of culvert trash screens, replacement of undersized culverts, removal of channel debris, and construction of waterbars on slopes.
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