Vancouver  A Century of Self-organized Rain
Abstract
Vancouver in British Columbia is a young city. It borders on steep mountainous terrain where landslides are relatively frequent. As the city expands onto hazardous terrain more is at risk. The landslides usually follow periods of prolonged rainfall culminating in short periods of high intensity. The frequency of heavy rainfall is therefore important in knowing when to expect and prepare for landlides and in issuing warnings. Vancouver has about a century of rainfall records for the airport station on the Fraser River delta where the incoming weather from the Pacific Ocean is relatively unaffected by orographic effects. Precipitation data is presented in both annual and monthly totals. The cumulative departure from the mean shows a drying trend for the first part of the last century, more or less average conditions for the middle part and finally a pronounced increase in wetness in the last part of the century. Two very wet periods in the early eighties and mid-nineties caused more landslide damage than at any time since settlement began in this part of Canada. Individual storm events on the North Shore mountains of Vancouver are also examined as power law distributions. Despite the complexity of precipitation, both annual and monthly values follow power law distributions. This remarkable finding allows estimates to be made of the probability of occurrence of damaging amounts of precipitation which is useful for risk management and engineering purposes. The probability of even more extreme events is predictable and is of interest to insurance companies.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.3978S