much of the north side and a large part of the center of the city was destroyed in 1941 by floodwaters and avalanche debris because of a burst reservoir that was the city's municipal water supply. the reservoir dam was about east of the town and more than 200 meters elevation above it. the dam failed because of sudden overflow pressure from an avalanche of glacier ice probably caused by a localized tremor (earthquake). within a few minutes the stream bed was filled with an avalanche of water, mud, boulders, and associated debris whose crest by the time it reached the city may have exceeded 15 meters height above the stream bed. in as few as four minutes after the dam burst the avalanche obliterated and covered the city's most modern suburb and destroyed most of the north half of the city.