news from the waterfront by Tim Matson


Had enough of record busting cold temperatures and snowfall east of the Rockies? Spring is on the way, as March forecasts show an upward temperature trend. Alas, it's not quite time to drop your guard. The frost has drilled deep into the ground. Snow piled up without the occasional relief of a January or February thaw is holding up to 10 inches of stored water. Ice on ponds is 1.5 ft thick. So what does this mean for pond owners?

Thaw means Water

Believe it or not there's a pond under there. When spring arrives runoff may stress the pond inflow and spillway. Keep an eye out for erosion, sedimentation, and flooding during ice out.

You want to watch your overflow systems to be sure frost-heaved terrain hasn't messed with your spillway system. If you have an underground pipe overflow, deep frost can move pipes around. When that longed for spring melt does arrive (and even before), pond overflow and ground water can work out around the outside of the pipe. If the exterior flow is strong enough, erosion can trigger a leak around the pipe, and lead to spillway failure and perhaps a blown out dam. If you see something like this happening get your contractor over for a look. Instead of letting the erosion worsen, you may want to pump the pond down, or dig out the channel and slowly lower the water so you don't lose the pond in one burst. If you have a drain, you may want to open it and let the pond down slowly, to avoid further erosion.

Spillways and culverts can freeze solid in harsh winters. If the pipe is blocked, spring melt will find another way out of the pond, and possibly do damage in the process. This is where an emergency spillway can come to the rescue. Or perhaps a contractor with a steamer that can thaw out the frozen pipe. A natural spillway stream might be blocked by ice, and need work to avoid blocked overflow breeching the dam. 

Spring is Coming

With up to ten inches of water locked up in the snow,
this year's spring ice out may test pond
flood control design.

If your pond is fed by an inflow stream, sudden big runoffs can trigger erosion. Result: damage to the stream and sediment in the pond. There's not much you can do at this point, unless you can turn off the stream or divert it. Mostly, you'll want put stream stabilization on your chore list. And consider installing a sediment pool in the stream to trap eroded material before it gets to the pond.

March 1, 2015

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