What will happen when all this snow melts?

By Jim Hegarty, P.E.

Our survey staff braving the drifts.

I just returned from a warm vacation, and whenever I’m away, I always wonder what’s going on at home. This time, I wondered how much more snow could pile up in my driveway. Answer: six inches! As I look out my office window right now, it’s still snowing.

I’m already dreaming of warmer weather, but I’m also considering the effect of the snowmelt.

There’s going to be flooding when the snow finally melts. Since the snow is piled high over most storm sewer inlets, the water from the melting snow won’t have anywhere to go except to flood the streets. Eventually, as the snow continues to melt, the water will enter the nearest river, which will swell and we’ll have our annual “spring floods.”

While I hope the following three phenomena don’t conspire to cause rampant flooding this year, the potential for a perfect storm exists, because:

  1. We need to melt a much higher-than-normal snowpack. Warmer weather causes snowmelt, which, coupled with spring rains, adds to runoff volume. When my snow melts, it ends up in the Grand River, which last year saw record rain-induced flooding.
  2. Rain only accelerates snowmelt, and when coupled with frozen ground, water that would ordinarily soak into the ground flows overland directly to the river, increasing the intensity of flow into the river.
  3. Finally, when ice jams form, water backs up for miles on some rivers until the ice jam clears.

Even though you are tired of moving snow, Get your catch basins exposed! —at home, work, your kids’ school, church . . . Let’s do what we can to limit the mess this spring.

For a more technical explanation, here is some more information from NOAA’s Grand Rapids office:

http://www.crh.noaa.gov/images/grr/presentations/Unusually_Deep_Snowpack_Spells_Flooding_Concerns_for_Southwest_Lower_Michigan_2014-02-06_17-13-48.pdf

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