Flooding Narrative

Waterton-Glacier International Peace Park (W-GIPP) also affects its surroundings (as opposed to the surroundings affecting the Park). The weather patterns of the area ensure that W-GIPP has many times as much moisture as the surrounding valleys. When high moisture is stored in the form of snow and the spring melt is faster than usual, flooding occurs in the lower reaches of the Flathead, Belly, St. Mary and Waterton River basins.

Flooding is normal. When discussion about flooding refers to a “100-year-flood”, it means that this kind of flood will happen every 100 years – at a minimum. It may happen more often than that, but it will happen during any 100-year span.

In June 1964, the Middle Fork of the Flathead River reached 8300 cubic feet of water per second (cfs), compared to a previous high of 700 cfs. People living along the Flathead river near Kalispell, especially the low-lying Evergreen area, were wiped out. American taxpayers shell out 2 billion dollars every year to cover flood damage. Canadian costs are less because of zoning regulations.

If floods happen every year and big floods happen during a normal lifetime, why do we spend so much on damage by floods? The reasons are clear. More and more people build their homes and businesses in the floodplain, playing their own version of Russian roulette with 50 and 100-year floods. With development comes pavement and concrete, which exaggerate the speed of water runoff and make floods worse. Water quality is also affected because petroleum, pesticides, septic system waste and soil sediments wash in with the water.

In Flathead County, many hundreds of homes sit in the 100-year floodplain, and conditions are better in the other river systems draining W-GIPP only because they are more sparsely populated. There will be disasters there someday, as well – just fewer in number.

We all want the waterfront house with the view. And some of us want someone else to pay the price for our risk. Many areas now disallow building in the yearly floodplain, but still allow buildings below the 50-year flood water level. Variances, special exemptions by the government agency in charge of building permits, are granted liberally.

The economic incentive for the government agency is this: more buildings equals more tax revenue. The risk is then transferred to the taxpaying public through the variance process.

Waterton-Glacier supplies clean, clear water to those in the valleys below – in widely varying amounts every year. What we do with it, and how we treat the water downstream from us, is up to us.


Flooding in Glacier
Winters in Glacier National Park are known for their massive accumulations of snow. The average snowfall in the high country is over 10 feet and snow depth at the "Big Drift" during spring plowing of the Going-to-the-Sun Road often exceeds 60 feet! Spring weather usually determines whether or not hydrologic activity will be in the headlines. In 1964 a heavy winter snowpack combined with warm spring rains to produce catastrophic flooding over large areas of the Park as well as portions of the Flathead Valley. Floods have also damaged the Polebridge area (on the North Fork) and flooding periodically occurs in the St.Mary River system, especially along Divide Creek near the village of St. Mary. In November 2006, the park experienced severe flooding, requiring extensive re-construction on the Going-to-the-Sun Road as well as many park bridges and trails.

Despite the potentially destructive impacts of flooding in developed areas, the sculpting action of water runoff is a natural force that profoundly influences Park landscapes. Without the periodic scouring and cleansing effect of floods and high water, stream channels would fill with sediment and silt and become clogged with woody debris. Substrate gravels on stream bottoms, essential habitat for fish spawning, would be covered over with silt rending them unsuitable for egg incubation. Moreover, they could not sustain aquatic invertebrates which comprise an important food item for fish.

USGS scientists and park biologists routinely measure stream flows and other hydrologic variables to monitor trends over long periods of time. Mountain streams are fed by glacial meltwater that provides a base flow late in the summer when precipitation is low. Global climate change over the next 50 to 100 years may significantly alter regional precipitation patterns and change both the timing and amount of spring runoff. As climate warms and glaciers melt, less water may be available during the hottest and dryest part of the summer.

Last updated: August 5, 2016

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