‘No Snow’ December Could Mean Spring Floods in Montana

Missoula, MT (KGVO-AM News) - We are well into December, and Missoula and western Montana have had very little snowfall to go with the colder temperatures.

Dr. Peter Kolb with MSU Extension and the University of Montana W.A. Franke School of Forestry and Conservation appeared on Talk Back late last week and sounded a warning for western Montana.

The Lack of Snow Cover Could Bring Spring Flooding

“Normally when we get an average snowpack, and by now we've got a foot or two of snow on the ground, it insulates the soil and keeps the soil from freezing,” began Dr. Kolb. “That's very important because decomposition rates in Montana are very, very slow. Typically it doesn't occur very much in the summer, because everything dries out too much, and all the microorganisms and the fungi that break down organic matter need moisture.”

Kolb explains why early winter snow is so important.

Dr. Kolb Explains the Science of Snow on Frozen Ground

“This is actually the time of the greatest level of decomposition, because the snow creates a humid, wet, thermally protected zone so that organic layer that's on the soil surface and that decomposes all winter long, and then the spring, when the plants become active, that decomposed organic matter, just like a compost pile, releases its macronutrients and micronutrients, and there's a flush of growth in the trees and the plants,” he said.

Kolb was clear about what may happen this winter into spring, due to the lack of snow.

“When we don't have snow, that organic layer freezes solid,” he said. “If you go out there now the ground is like concrete, and all those organic layers are frozen. Your compost piles, unless they're fermenting inside and producing their own heat, are also frozen. When we have winters like this, that start out where the ground is frozen, decomposition stops. I mean, all that organic stuff is put in the deep freeze, and so we're going to see kind of a nutrient imbalance in the spring, that plants aren't going to have that fresh organic matter unless we have a very slow, wet spring. There's a lot of catch up that has to occur during that time.”

Dr. Kolb Said Home and Landowners Should Prepare for Possible Spring Flooding

Kolb said due to the frozen ground conditions, spring may bring flooding.

“When the ground isn't frozen, that snow melts and the water gets absorbed by the soil,” he said. “When the soil is frozen and we get a snow pack on top of it, that soil will remain frozen because it's now insulated and protected by the snow, and the water is going to run off on the surface. This is a precursor to spring flooding, because the soil can't absorb that. Think of all that forested area out there. The ground is frozen. It can absorb moisture and it is dry. I mean, we didn't get that fall moisture out there, but that frozen ground in the spring is going to shed water like a raincoat.”

In other words, since the ground is already frozen, melting snow won’t penetrate the soil, and flooding may occur.