Warm-up, rain bring chance for flooding

Alexander Sinn • Feb 2, 2019 at 10:00 AM

Michigan residents are rejoicing the end of arctic conditions as the polar vortex releases its grip on the region this weekend, but there is some risk that warming temperatures and rain could lead to flooding.

The temperature is expected to reach above freezing today for the first time in more than a week, with some melting snow. Light rain and drizzle will also move into the region, according to Brandon Hoving, a meteorologist with the National Weather Service in Grand Rapids. 

“What that will tend to do is it’ll chip away a little bit at the snowpack, but the snowpack is so deep it’ll probably absorb a lot of that rainfall and compress a bit,” he said. 

Sunday could see the temperature reach into the lower 40s, with as much as a quarter-inch of rain expected by the end of the weekend, Hoving said. 

Rain is also expected Monday, with temperatures that could reach 45 degrees, but the total rainfall is not expected to lead to flooding on its own. The warming could cause ice to break up along the Grand River and begin flowing, Hoving said. 

Local officials are preparing for potential ice jams on the Grand River, and are concerned about drains and catch basins impeded by ice and snow.

Ottawa County Emergency Management Director Nick Bonstell said the Grand River in Ottawa County is currently at the 10.5-foot mark, with about 3 feet to grow before it reaches its maximum level. While the river will likely not overflow due to rain, ice jams in the river could cause flooding to occur.

“If we get a small ice jam, that really puts us at risk for being able to respond quickly,” Bonstell said. “The ice jam is probably the biggest thing we’re watching.”

County officials monitor the river through field gauges, which feed information to a map that shows changes in color as the river rises. Officials also drive along the river to make physical assessments, Bonstell said.

Ice jams occur regularly in the river, he explained, including significant jams in 2008, 2013 and 2015. The 2015 jam was never physically located, Bonstell said, but its effects were felt through flooding.

Jams are common beneath the drawbridge in Grand Haven. Robinson Township typically sees the first flooding if a jam occurs, Bonstell said.

Local agencies such as law enforcement, the Ottawa County Road Commission and the National Weather Service collaborate to prepare for potential flooding, Bonstell said.

“We’re being very proactive,” he said.

While above-ground snow and ice may melt with daytime highs in the 40s, the ground will likely remain frozen, unable to absorb the water.

“When the temperatures get up that high, it’s not enough time for the ground to thaw, so water that drains from snowpack has nowhere to go,” Bonstell said.

Grand Haven Public Works Director Derek Gajdos said the primary concern within the city are catch basins, such as ditches and storm drains, many of which are covered or blocked by snowbanks.

The city is prepared to stop the river overflowing with sandbag barriers, Gajdos said, but it hasn’t had to deploy these measures in recent years.

Residents can help out by shoveling off storm drains and uncovering ditches, he said. The city’s storm sewer system is able to handle a large volume of melt and rain water if the basins are cleared, Gajdos added.

Ottawa County officials suggest residents who have sump pumps to check to see if they are plugged in and working. Snow should be dug out of window wells and basement exterior stairwells, and shoved several feet away from outside doors to allow water to flow away from the home.

Bonstell said it is important to know where your home’s water shutoff is located in order to limit the damage in the case of flooded pipes. Local fire departments are called out regularly for broken sprinkler pipes, he said.

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