Agencies and residents prepare for possibility of flooding –
By Michael Howell –
Predicting exactly when and how high the Bitterroot River may crest in the spring is a notoriously tricky affair. It depends on a complex constellation of many variables. But officials at the National Weather Service, based on an analysis of snow pack in the area combined with current and forecast weather conditions, are predicting record setting high flows at the Victor measuring gauge by the end of the month.
Looking at a summary hydrograph of water levels in the Bitterroot River near Darby from the years 1938 through 2009, it is evident that the peak runoff period traditionally falls between the last few weeks of May and the first few weeks of June. This year the snow melt-off has been slowed by an unusually cold and wet spring. According to data on the National Weather Service’s web site, on Sunday, May 15, the snow water equivalent (SWE), measured at various sites in the Bitterroot, shows well above average water content remaining in the higher elevations. At the Nez Perce station, SWE was measured at 249 percent above average, at Daly Creek 427 percent above average, at Moose Creek 191 percent above average, at Skalkaho 134 percent above average and at Saddle Mountain 144 percent above average. This means there is a lot of water still to run off the mountains and into the Bitterroot River. The overall river basin is calculated to be 161 percent above average for SWE.
Although run off has begun in earnest, forecasters were predicting Sunday that cooler temperatures with rain and snow in the higher elevations this week would slow the process up with actual flow levels predicted to drop. But that is forecast to change over the weekend when river levels will begin to rise once again and possibly reach a record setting high near Victor, perhaps by the end of the month. The river is expected to reach flood stage in the Darby area around the end of the month as well.
Flooding along the river is only a part of the scenario, however, as many small streams are also expected to top their banks across Western Montana. The National Weather Service in Missoula issued on Sunday a small stream flood advisory for melting snow in Ravalli County. In particular, Eight Mile Creek was noted to have reached bank full, threatening some culverts and county roads in the area. They cautioned that other area creeks and streams will be running high during at least the next several days and could cause minor flooding in low lying areas. Local storms and thundershowers could aggravate the situation.
National Weather Service officials also caution recreationists that all area rivers and streams will be running high and fast for quite some time. They urge weekend recreationists to exercise caution if they plan to be on or near the river, and to keep abreast of the latest weather reports.
Ravalli County Disaster and Emergency Services Director Ron Nicholas told a small crowd at Stevensville Town Hall last Saturday that residents who may be facing flooding problems have the unique opportunity to get some help in advance in the form of sand bags donated by the Army Corps of Engineers. Nicholas said that usually ACE only distributes sand bags to areas that have already been declared a disaster. But due to an excess of about 200,000 sand bags at Libby and over 1.5 million extra sand bags in the Seattle area where they had been preparing for a dam break that did not materialize, the agency decided to make sand bags available around the state. Ravalli County got 16 pallets.
The sand bags are available to county residents for free at all Ravalli County fire stations. To obtain the sandbags, residents need to contact their local fire chiefs. Their phone numbers can be obtained by going to www.ravallifirecouncil.org. Nicholas urged residents to obtain the sand bags from the Fire District within which they reside, even though sand bags are being made available all over the valley.
Sand is available at the Ravalli County Fairgrounds, Corvallis Fire Station No. 2 on the Eastside Highway, Victor Fire Station, the water and sewer plant in Stevensville, Florence Fire Station and at Painted Rocks Dam.
Trapper Creek Job Corps has volunteered to fill bags with sand, but will not tote them anywhere or place them anywhere. The Red Cross, according to local coordinator for the Red Cross Dallas Erickson, will not deal with sand bagging or sand bags at all, but will supply food and drinks to volunteers who help do those jobs. They also offer, of course, emergency shelter for those misplaced by disaster. He said anyone needing emergency shelter should call 1-800-ARC MONT and they will be directed to the most immediate shelter available at the time.
Both Nicholas and Erickson explained the details of “sand bagging,” that is the art and science of laying down a wall of sand bags that is not going to get washed away in the flood. For one thing, according to Erickson, you should lay the bags parallel to the flow of water as much as possible and avoid trying to block or cross a current. The rule of thumb is not to stack them higher than the bottom is wide, unless they are being propped up next to a solid structure such as a wall that can stand the force of the water.
It would be wise, he said, to consult local authorities, especially the road department, if a roadway is involved, prior to placing the bags. Erickson said that he spoke from experience on that one, having made that mistake once.
Nicholas said that emergencies had already been declared in Lincoln and Lake Counties and that the Ravalli County Commissioners were going to consider a declaration on Tuesday, May 17. Nicholas said that by declaring an emergency ACE could make more sand bags available that might be placed in time to prevent some flood damage.
The highest crest recorded on the Bitterroot River, according to Nicholas, was 8.55 feet at Darby on May 17, 1997. In descending order the river crested at 8.45 feet in 2003, 8.42 feet in 1974, 8.26 feet in 1996, and 8.08 feet in 1947.
According to information provided by NOAA, in terms of flow in cubic feet per second, the largest flows since records were started in 1938 were 11,000 cfs on two occasions, once in 1947 on May 9, and once the following year in 1948 on May 26. Forecasters predict that by May 26, 2011, the river will crest the highest ever in the Victor area and surpass all historical records at that gauging site.
Nicholas said that every agency in the county, the state and the federal government that deals with emergencies was aware of the flooding threat in Montana. Nicholas said that if a person lives near the river and wonders if they live in a flood hazard area they can contact County Floodplain manager Eric Anderson and get a quick initial determination based on the latest LiDAR mapping which is accurate to within two feet in elevation.
Erickson said that the most valuable aid received in almost every emergency is the immediate aid rendered by family, friends and neighbors. He noted that a power outage over a wide area did not constitute an emergency until after 72 hours. He said people need to be prepared with emergency essentials to last a 72-hour outage at a minimum. Whether aid can be delivered even after 72 hours is also a question. He said that in some instances power has not arrived for weeks.
Both men cautioned people about driving through water that might look shallow. Studies show that under the right (or wrong) road conditions at a certain velocity it only takes one foot of water to sweep an automobile up in its current. It only takes two feet of water to float the average automobile due to its buoyancy. It will float and drift in the flood flow before the water reaches the level of an open window.
Nicholas urged the public to call 9-1-1 if they faced an emergency situation. He said where authorities know of flooding in a certain area of the county it can use what he calls Reverse 9-1-1, a program in which every phone number listed in the phone book can be called up with an emergency warning message. He said such messages may warn about the potential need for an evacuation. In the case of an actual evacuation, he said, it is implemented by the Sheriff’s Office and an officer would be knocking on their door. Nicholas also noted that people who don’t have a land line listed in the telephone book may have their cell phone numbers recorded at the 9-1-1 center and included on emergency “call ups,” such as a flood notice or fire notice in their neighborhood. Anyone interested in registering their cell phone number with the emergency services can do so by calling 363-3033.
Ravalli County will establish a designated flood line at the county’s emergency operations center. Ravalli County has an agreement through the Montana Red Cross to establish shelters at a number of local schools if the need should arise. Nicholas said people have rarely used those shelters following evacuations due to flooding. Nicholas’ office can be reached at 375-6655.
Mayor Lewis Barnett of Stevensville reminded residents that flooding in town often occurs around Spring Street and along Burnt Fork Road. He said both those areas can flood, especially if debris blocks up the ditches.
The town’s sewer treatment facility may also be in jeopardy since it is located in the river bottom west of town. The town has never participated in the federal flood insurance program which makes funds available for pre-emptive work on mitigating flood hazards. Councilor Desera Towle said that the town council was currently working on joining the federal flood insurance program. It would also make the purchase of homeowner flood insurance more affordable for a few Stevensville residents that actually reside in or next to the floodplain.
Anyone wondering how best to prepare for a flood can check the U.S. Search and Rescue Task Force website for lots of good information at www.ussartf.org/flooding.htm.
Constantly updated charts showing water flow at gauges in Montana’s major rivers, including the Bitterroot River at Darby, Victor, and Missoula, snow pack, etc. can be accessed on the internet at the Northwest River Forecast Center of the National Weather Service, a division of the National Oceanic and Atmospheric Administration (NOAA). Go to www.nwrfc.noaa.gov/rfc/. It is also a good site to check on the weather.
Nicholas noted that someone is affected by flood or drowning almost every year. It doesn’t take a huge snowpack. It depends on timing and temperature a lot. He said the river surprises us every year with sudden changes in channels or the movement of huge masses of debris that can wreak their own path of destruction.
“Peak flood times in the Bitterroot are always dangerous,” said Nicholas.