Abstract:The glaciers of western Canada and the conterminous United States have dominantly retreated since the end of the Little Ice Age (LIA) in the nineteenth century, although average rates of retreat varied from strong in the first-half of the twentieth century, with glaciers stabilizing or even advancing until 1980, and then resuming consistent recession. This retreat has been accompanied by statistically detectable declines in late-summer streamflow from glacier-fed catchments over much of the study area, although there is some geographical variation: over recent decades, glaciers in northwest BC and southwest Yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat, and glacier-fed streams in that region have experienced increasing flows. In many valleys, glacier retreat has produced geomorphic hazards, including outburst floods from moraine-dammed lakes, mass failures from oversteepened valley walls and debris flows generated on moraines. In addition to these hydrologic and geomorphic changes, evidence is presented that glacier retreat will result in higher stream temperatures, possibly transient increases in suspended sediment fluxes and concentrations, and changes in water chemistry. With climate projected to continue warming over the twenty-first century, current trends in hydrology, geomorphology and water quality should continue, with a range of implications for water resources availability and management and hydroecology, particularly for cool and cold-water species such as salmonids.

Debris flow frequency and magnitude were determined for 33 basins in southwest British Columbia. Basins were first classified as either weathering-limited or transport-limited using a discriminant function based on debris-contributing area, an area-weighted terrain stability number, and drainage density. Multiple regression was used to predict magnitude, peak discharge, frequency and activity (frequency times magnitude) within each group of basins. Model performance was improved by stratifying the total sample of debris flow basins into weathering-and transport-limited groups. Explained variance increased by an average of 15 per cent in the transport-limited sample, indicating that sediment supply conditions in the more active basins are fundamental in predicting debris flow activity. An independent test of the regression models with 11 basins yielded generally good results for debris flow magnitude and peak discharge. Prediction of debris flow frequency proved problematical in weathering-limited basins. The methods developed here provide estimates of debris flow attributes in basins for which few data on past events are available.

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Abstract.A large rock avalanche occurred at 03:27:30 PDT,