Watch out for ice jams as temperatures rise - KMSP-TV

Watch out for ice jams as temperatures rise

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Meteorologist Cody Matz Meteorologist Cody Matz
(KMSP) -

It's that time of the year...finally! Spring is arriving and so are the spring-like temperatures. With the warmer weather, of course comes the snow melt which can have negative effects on local land.

Most of us heed the warnings when it comes to thinning ice, but we forget about the threat from flooding which can occur even in years that widespread flooding is not expected. Most of this comes from ice jams, which is the most common source of flooding along creeks, streams, and rivers.

An ice jam is simply what it sounds like -- a buildup of ice along a river because something is blocking the flow of the river.

This can cause a rapid rise in river levels upstream because the speed of the rest of the river doesn't change leading to a bulging of water right around the jam up. These ice jams are far more prevalent in colder years where there is more and thicker ice.

Here is an example of just how quickly water levels can rise because of the breakup of ice. Below is an example from a National Weather Service hydrograph that shows the river level at one point along a stream.

This shows 2 different ice jams in one location… the second of which shows a 5 foot rise in the river over just a 12 hour period pushing this particular river above flood stage. This is just one example, in some cases, river levels can get pushed several feet above flood stage in just a few hours' time.

So there are many things to watch out for because there are many different types of ice jams… here is a list of some of the different ones.

The more common areas to get ice jams are around bends in the rivers, usually the tighter curves, and obstacles like bridge supports. But with a very thick layer of ice on many rivers and plenty of snow to melt, the chances for scattered ice jams is pretty likely so pay close attention over the next few weeks.


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