Improving dam safety analysis by using physically-based techniques to derive estimates of atmospherically maximum precipitation (British Columbia)

A high or very high consequence dam is a large dam whose failure would have large consequences to life and/or property downstream. Knowledge of the magnitudes of extreme floods and their associated annual exceedence probabilities (AEP) are needed to determine the risk that such a dam might fail.; Traditionally, the largest “physically possible” precipitation event (the Probable Maximum Precipitation, PMP) and its associated flood event (the Probable Maximum Flood, PMF) have been calculated with a combination of statistical and meteorological techniques developed by the World Meteorological Organization (WMO). These techniques work reasonably well in flatter terrain, but may occasionally produce unrealistic results in mountainous terrain. This research focuses on improving safety studies for hydrologic structures such as dams, by using physically-based techniques to estimate the PMP and PMF and to calculate the associated AEP. This research contributes in three areas. The first area is in using an atmospheric model to estimate maximum precipitation. Secondly, the research demonstrated that simulated streamflow may be used to generate frequency curves and their associated confidence limits. The final contribution was in demonstrating that the frequency statistics indicated that the traditional PMP overestimates the PMF, while the atmospheric model estimates were more in line with accepted AEPs for a PMF.; This research was performed on the upper Columbia River Basin in southwestern British Columbia. The basin is an alpine basin, with annual precipitation varying from 2500 mm on the west to 500 mm on the east. Severe precipitation events generally begin over the Pacific Ocean, but are somewhat moderated by the intervening mountain ranges. There are several hydroelectric and flood-control dams operated by BCHydro on the Canadian portion of the river. One of these, Mica Dam, was used as the focus of this research.; This research has improved the current methods for safety analysis of hydrological structures, and recommends the use of physically-based methods to derive PMPs and PMFs. (Abstract shortened by UMI.)...