Flood planning underway

Drawing on the lessons they learned from the all-time record Flood of 1997 when the Minnesota River crested just short of 24 feet — 10 feet above flood stage — Montevideo city officials are preparing for what could well become known as the Flood of 2010.

What was originally intended to be a table top exercise turned into an actual staff planning session Thursday afternoon last week at City Hall. City officials and department heads met with representatives from the National Weather Service, the Minnesota Army National Guard, and Chippewa County to clarify who would do what and when.

Local authorities need to coordinate the efforts not only of city departments but also national, state and county agencies, as well as volunteer agencies such as the Red Cross and Salvation Army.

“We need to keep in mind there’s lots of different players doing a lot of different things,” said Montevideo City Manager Steve Jones.

The issue is not whether there will be a flood this year, but how bad a flood it will be. The National Weather Service predicts a 40 percent probablility of reaching last year’s high of about 18.5 feet. There is about a 3 percent chance to reach the 1997 level of nearly 24 feet.

The estimates will change over the next six to eight weeks as weather conditions dictate.

Based upon data presented by Diane Cooper, service hydrologist with the National Weather Service office in Chanhassen, the elements are all in place for at least moderate flooding.

“The Red River looks bad, but the Minnesota River doesn’t look peachy (either),” said Cooper.

October rainfall in the watershed was over 300 percent of normal, and there is a lot of snow on the ground in the headwaters area of the Minnesota River.

From Dec. 1 until Feb. 9, there was 175 percent to 200 percent of normal snowfall in the upper Minnesota River basin. There is 3.5 inches to 4 inches of water in the snowpack, which is between 200 percent and 300 percent over normal for liquid precipitation for the headwaters waiting to melt. Overall, there are 4 inches to 6 inches of water in the snowpack in the Minnesota River watershed.

“Because of the December freeze, that water is kind of frozen in place in the system,” said Cooper.

Because the ground is saturated, the water cannot soak in but will instead run off. “The sponge is full,” said Cooper.

Widespread flooding — called aereal flooding — other than in river valleys is a concern

And there is still potential for above normal additional precipitation for February and March, said Cooper.

Also, the NWS models do not include ice jams and the effect they can have on the flow of floodwaters. Cooper asked that ice jam information be reported to the NWS immediately so they could be factored into ongoing condition reports.

Cooper warned that curiosity seekers should be kept off ice jams, which are inherently unstable.

Aerial surveillance flights are a very useful tool for the NWS and local authorities to keep abreast of flood conditions, Cooper added. Also, infrared equipment in aircraft can help forecasters determine how much moisture is contained in the snow cover.

Cooper recommended that the city flood headquarters use nws.chat.weather.gov to stay abreast of developments. The public can keep up by going to ahpsmobile.wrh.noaa.gov, which allows subscribers to pull up any available river’s hydrograph quickly on any Web enabled mobile phone browser or at any computer.

Not only were the NWS representatives able to explain how they arrived at their forecasts, but they benefited from sitting in on the discussion as well.

“This has been a very helpful experience for me,” said NWS hydrologic forecaster Dustin Goering. “It will help us focus (when we make flood forecasts).”