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Spring Conditions Near Normal, But Near-Term Flood Potential Elevated
March 3, 2011
AUGUSTA, MAINE — Despite snowpack, ice conditions, stream flows and headwater storages that are in the normal range for the time of year, flood potential is elevated in the short term, as warmer weather and rain are expected in many parts of the State this weekend. The Maine River Flow Advisory Commission, meeting today in Augusta, reviewed information on current hydrologic conditions across the state, as well as short-term weather forecasts.
The National Weather Service is closely monitoring a storm system that could bring significant rain to central and southern sections of the State over the weekend. Although mountain and northern areas could receive more snow, southern and coastal Maine may see temperatures into the 40s or 50s and significant rainfall on Sunday and Monday. Warm temperatures, coupled with rain, could cause at a minimum street flooding, and potentially stream or river flooding. Higher stream flows could also raise and move river ice, possibly causing ice jams.
All Mainers should monitor National Weather Service forecasts closely, as it is not clear how much precipitation this storm will produce, and what the balance of snow and rain will be.
The concern with this storm demonstrates clearly that the most important factor influencing flooding is rainfall. Significant rain could cause flooding even though other risk factors (snowpack, river ice and stream flows) are all in the normal range for the time of year.
Much of state has 6 to 9 inches of water in the snowpack, according to this week’s cooperative snow survey. There is a little less water in southern and far northern sections. Currently, the snowpack is quite dry, and can absorb some amount of rainfall. These levels put water content in the normal range across much of the state compared to historical averages. However, portions of south-central and eastern Maine are in the top 25% of historical levels, and much of Hancock and Washington Counties is in the top 10% of historical levels.
River ice is in the normal to below normal range statewide. The US Coast Guard is once again planning to break ice in the lower Kennebec River, downstream from Gardiner. The Coast Guard will partner with the USGS to measure ice thickness, and will then coordinate with DOT, Maine Marine Patrol and MEMA to plan an ice-breaking schedule.
Stream flows likewise are normal for the time of year. Rain in December brought streams in eastern Maine up sharply, causing localized flooding and washouts. However, since December streams have come back to near normal flows everywhere in the state.
Reservoir storages in the headwaters of Maine’s large rivers are being drawn down to prepare for spring rains runoff. River basin managers report that they are on track to achieve their drawdown targets.
Everyone should stay aware of current forecasts, according to Rob McAleer, Director of the Maine Emergency Management Agency, and co-chair of the Commission. “We’ll be watching this weekend storm closely,” McAleer said. “Too much rain and a rapid warm-up could create problems for us, even though the snow pack can absorb a good deal of rain. Residents and business owners should also monitor local conditions closely.”
McAleer noted it is most important to check your flood insurance coverage if you live or have a business in a flood-prone area. “Most home and business owner’s policies do not cover flood damages. And there is 30-day waiting period before a new policy goes into effect,” he said. “The time to check your insurance is now.”
Commission members will stay in close communication throughout the spring season, and will meet again if conditions warrant. Snow surveys will be conducted each week from now until the snow cover is gone.
The River Flow Advisory Commission meets annually in late winter to share information, examine potential for spring flooding and to renew operational protocols. The Commission is composed of state, federal and industry representatives with an interest in hydrologic issues. The full report of the March 3 meeting will be available on the Internet at http://www.maine.gov/rfac.