PERMAFROST FAVOURABILITY MAP OF BRITISH COLUMBIA

A wide variety of very large rock avalanches and an increase of reported rock fall and debris flows from many of the world’s cold mountain regions, raise the concern that climate change is reducing slope stability. Permafrost warming and thaw is one of the possible explanations for this observed ongoing change, a hypothesis which is supported by different case-studies and process investigations. To this end, an estimate of potential permafrost distribution and its characteristics is useful for a forensic reanalyses of past events and for predicting where changes in hazard potential may be expected. For British Columbia only extremely coarse mapping of mountain permafrost distribution has been available up till now. Typical empirical-statistical approaches cannot be applied due to sparse ground temperature data over a large and heterogeneous area.

To achieve a permafrost estimate we transferred existing permafrost models from comparable mountain ranges to British Columbia: We combined regional spatialized estimates of mean annual air temperature with topography controlled potential solar radiation to obtain an estimate of mean ground temperature throughout BC by applying the empirical relations found in other mid-latitude mountain ranges. Further, an illustrative interpretation key helps to interpret the map in consideration of the locally observable surface conditions. Distributed data from seven field sites are used to demonstrate the model validity and to give a rough estimate of the model uncertainty. The resulting map suggests that a large part of BC’s mountain ranges contains permafrost and several recent rock slope failures occurred in permafrost areas.