Causes of Flooding in Drumheller - Town of Drumheller |

Town of Drumheller

Town of Drumheller

Causes of Flooding in Drumheller

Ice jams (frozen water)

These jams result from the accumulation of ice fragments that build up to restrict the flow of water and then act as a temporary obstruction. Jams form during both the freeze-up (October to November) and break up periods (March to April) but it is usually the breakup jams that have the greater flooding potential.

Rain on Snowmelt runoff (flowing water)

During the winter, most of the precipitation is stored as snow or ice on the ground. During the spring melt, huge quantities of water are released which explains our heavy spring runoff and recurring flooding. This is called a freshet. These floods generally occur in the spring but can also occur during sudden winter thaws. Heavy runoff results from the rapid melting of the snow under the combined effect of sunlight, winds and warmer temperatures. When the ground is frozen, the water produced by the melting snow is unable to penetrate and runs off over the ground surface into rivers and streams. If there is an above average snow depth, a sudden thaw, or both, then the potential for high volumes of runoff and subsequent flooding increases. The situation can become of even greater concern if the rising snowmelt runoff is compounded by runoff from heavy rainfall. The later the thaw, the more likely this situation will prevail.

Rainfall (falling water)

Flash floods can be extremely dangerous. They usually happen on small watersheds as a result of a torrential downpour, often caused by heavy thunderstorm activity. A flash flood is characterized by the occurrence of the peak of the flood within six hours of the onset of rainfall. The flood conditions develop rapidly because the rainfall is so heavy the ground is incapable of absorbing the water quickly enough, resulting in a very high runoff rate. These events are generally locally intense and damage is usually restricted to a limited area.