In this lab we will be looking at the potential for generation of lahars and other volcanism-related floods in the area of Whatcom County around Mount Baker (Washington), and also within the Squamish and Cheakamus River valleys in the Garibaldi area.

Please bring copies of the maps of the Garibaldi and Baker areas. You should also have a look at a satellite image of the Garibaldi area, which clearly shows some relatively recent volcanic features. The image might help in understanding what could happen regarding lahars in the event of an eruption around Garibaldi.

Mt. Baker

Mt. Baker is one of several Cascade Range volcanoes which is considered to have the potential to erupt within the next 50 years. There were several eruptions at Mt. Baker in the 19^th century, and there were numerous small debris avalanches in the 1950's, 60's and 70's. Beginning in 1975 there was heightened thermal activity on the mountain, with emissions of gases and melting of ice and snow near to the summit.

Mt. Baker has a large ice cap - much bigger than Mt. St. Helens had prior to the 1980 eruption - and there is no doubt that a significant eruption would produce a huge volume of lahar flooding. Even a small eruption could impact some of the nearby towns, but a large eruption could affect some of the major centres near to the coast. There is plenty of evidence of past lahars in the valleys surrounding the mountain.

A map of the Mt. Baker area is provided. Some of the towns and cities are shown, and you should assume that wherever there is a town on a river that that town could be seriously affected by a lahar flood of that river. Glacial ice is shown in white.

There are two artificial lakes on the eastern side of Mt. Baker (Baker and Shannon Lakes). It is predicted that the dams could be over-topped (or even damaged) if there was a significant flood while the reservoir levels were high. Assume that the volume of lahar associated with a large eruption could be as much as 150 million cubic metres, and also that if the flood gates were opened the lake volumes could be reduced by 5 million cubic metres per day.

Your assignment is to predict the potential for serious flooding in each of the 6 communities marked (Ferndale, Bellingham, Abbotsford, Acme, Maple Falls and Concrete) under four different scenarios, as follows:

Note that while Abbotsford B.C. is not on the Nooksack River, there is a relatively low ridge between the two drainage systems. It is predicted that a major flood on the Nooksack River could spill over and impact the area around Abbotsford.

Indicate (yes or no) whether the various communities are likely to be affected by lahar flooding.

Garibaldi Area

The major rivers, glaciers and three of the volcanic centres of the Garibaldi area are shown on the map. While an eruption is not expected soon at any of these volcanoes, the potential for an eruption remains. Furthermore, all of the volcanic mountains in this region are potentially unstable in terms of their risk for landslides. In 1984 a small debris avalanche at Mt. Cayley briefly dammed up the Squamish River. 

Describe. in at least a couple of sentences for each. what is likely to occur during the following scenarios, and how the communities of Brackendale, Squamish and within the reserve areas on the Squamish River might be affected: