Abstract
Estimation of the Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF) are regulatory requirements in many jurisdictions that are used in the design of dams and assessment of existing infrastructure. The recently available British Columbia MetPortal provides regionally consistent PMP and precipitation frequency estimates across the province of British Columbia (BC). This paper proposes an approach to process and apply this data for the estimation of the PMF for watersheds across British Columbia. Guidelines are presented for selection of transposition points applicable to a watershed, and algorithms are developed for processing the geospatial probable maximum storm and precipitation frequency data. The algorithms developed are generic to multiple software and programming environments, and could also be applied in other regions where spatially and temporally intact PMP estimates are available. A detailed description of data sources and development of PMF scenario inputs is provided, as well as details of important sensitivity analyses. The methodology is applied to estimate the PMF for the Cheakamus Basin north of Squamish British Columbia. The application of the MetPortal PMP and precipitation frequency estimates, when used with a consistent PMF development methodology as proposed in this paper, will help improve the consistency of PMF estimates for watersheds across the province, offering a welcome improvement for dam owners and regulators.
Highlights
The Probable Maximum Flood (PMF) is the theoretical maximum flood that can reasonably be expected to occur for a given location
This paper presents a methodology for the application of the British Columbia (BC) MetPortal Probable Maximum Precipitation (PMP) and precipitation frequency estimates to evaluate the Probable Maximum Flood (PMF)
PMP and PMF estimates are being used for dam-safety assessments throughout the world
Summary
The Probable Maximum Flood (PMF) is the theoretical maximum flood that can reasonably be expected to occur for a given location. It is derived based on the Probable Maximum Precipitation (PMP) or Probable Maximum Snow Accumulation (PMSA), in combination with other conditions—for example a precipitation event, snowpack or temperature sequence—not exceeding a 1/100 year Annual Exceedance Probability (AEP) [1]. In the CDA-recommended standardsbased approach to flood hazard, the PMF is used in the determination of target standards from High to Extreme consequence dams. PMP and PMF are by nature deterministic assessments of flood loading and do not provide the probabilistic information useful in analyzing dam risk [4]. Improvements in PMP and PMF estimation methods are still important and warranted
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