Highway 99, which links Whistler and Squamish with Vancouver, is already plagued by landslides and dedris flows from the precipitous Coast Mountains. An eruption producing floods could destroy segments of the highway. Flooding and debris flows could also have serious coneequences for the salmon fishery on the Squamish, Cheakamus, and Mamquam rivers. In addition,explosive eruptions and the accompanying ash could cause short and long-term water-supply problems for Vancouver and much of the lower mainland. The catchment area for the Greater Vancouver watershed is downwind from the Garibaldi area. Air-fall material could also have a deleterious effect on the ice fields to the east of Mt. Garibaldi, causing increased melting and spring flooding. This in turn could theaten water supplies from Pitt Lake as well as fisheries on the Pitt River.