The Free Press, Mankato, MN

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March 5, 2010

Flood threat in region unchanged

Situation is worse in Montevideo, Granite Falls

By Tim Krohn Free Press Staff Writer

MANKATO — Despite a heavy, wet snowpack, the Mankato area should escape serious flooding this spring, barring unusually heavy precipitation.

An updated flood risk assessment for the area is similar to one released two weeks ago by the National Weather Service.

There is still a 30 percent chance that Highway 169 between Mankato and St. Peter will be flooded this spring. There is a 30 percent chance for moderate flooding in the Mankato area and a less than 25 percent chance for major flooding.

The Weather Service is predicting virtually no chance the water would get high enough to near the top of the flood walls along Mankato and North Mankato.

Near low-lying Henderson, things will be more difficult.

There is nearly a 100 percent chance that Highway 19 between Highway 169 and Henderson will be closed, and an 85 percent chance Henderson will have to install its flood wall across Highway 19 where it enters the town.

Those percentages are up just slightly from the previous forecast.

The news is worse upriver, where there is an 80 percent probability of major flooding in Montevideo. Granite Falls is also at high risk.

This week Gov. Tim Pawlenty asked the Army Corps of Engineers to provide Montevideo with technical and emergency operations assistance.

The Corps said it has begun to draw down water levels behind dams in the Minnesota River watershed, which will cause water levels to rise in the Bois De Sioux and Otter Tail rivers and to rise in Breckenridge and Wahpeton. That could cause flooding during the next week to 10 days, the Corps reported.

There are five dams on the upper stretches of the Minnesota River, the last one just downriver from Granite Falls. They hold back water in Lac qui Parle, Marsh Lake and other reservoirs.

There is a 70 percent likelihood of major flooding along the Mississippi in St. Paul.

And the Weather Service says major flooding is certain in Fargo and Moorhead with a 25 percent chance it could reach last year’s record crest.

The probability of major flooding in Grand Forks and East Grand Forks is more than 50 percent.

Little snow has fallen recently, but the depth of the snowpack and its moisture content are similar to those in 1965, 1997 and 2001 — all years that produced heavy flooding.

That snowpack has been slowly melting in the Mankato region — something that should reduce later flood risk. But colder temperatures in the Fargo and Moorhead areas have left the deep snowpack in place. 

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