Dam Hydrologic Loading

These BC-specific resources related to extreme precipitation and flood data seek to support the determination of hydrologic loading on dam reservoirs and other critical civil engineering infrastructure. These resources may be applicable for the design of a new dam, completion of a dam safety review, design of a replacement or auxiliary spillway due to updated design criteria, or completion of a dam failure consequence assessment.

Organization Resource
Government of BC Ecological Reports Catalogue (EcoCat)
EcoCat provides access to reports on ecological activities in British Columbia, plus related files such as maps, datasets, and published inventories when available.

Note: Studies were completed using different datasets and methodologies, and were completed by different organizations, therefore, not all reported values will be the same. For example, watershed areas and flood quantile values of hydrometric stations vary by study.

Regional Flood Frequency Studies
There are different approaches available for completing a regional flood frequency analysis. Two common methods used in BC are the Index Flood (IF) method (also called the peak-flow method) and the Regional Regression Equations (RRE) method (also referred to as the direct quantile regression and the multiple regression methods):
  • Index Flood Method – The Ministry of Environment and Climate Change Strategy (ECCS) most recent streamflow inventory studies across BC are available as a series of separate reports. The reports provide streamflow statistical analysis, watershed area and median elevation of all active and discontinued Water Survey of Canada (WSC) hydrometric stations in BC. (EcoCat ID 59010, 58628, 52707, 53344, 48460, and 40801).
  • Regional Regression Equations Method – The Ministry of FLNRORD initiated a regional flood frequency analysis study using the RRE method (NHC 2020). Single station frequency analysis was completed for selected hydrometric stations in BC and surrounding province, territories, and states that met the study natural flow definition. The gauge reports for each hydrometric station analyzed include several physical and hydroclimatic characteristics of the respective watersheds. Regional flood quantile equations were developed using the RRE method. Regional analysis procedures were proposed using different available information for determining homogeneous regions (EcoCat ID 59125).
Water Data and Tools
Various information related to hydrometeorology is available on the BC Government Water Data and Tools website. Depending on the location of the dam, regional or municipal climate change studies may have been completed in a nearby vicinity. A literature review is required to identify if any of these studies exist in the vicinity of the project, as these studies often have more location specific downscaled climate data useful in informing the Inflow Design Flood values.

Water Tool Portal
The BC Water Tool is a map-based water information tool designed to provide a wide range of water-related data and information. The BC Water Tool was developed for FLNRORD and the BC Oil and Gas Commission.

Watershed Characterization
A few key resources have been developed by the BC Government for characterizing watersheds. The documents below outline basic watershed information that need to be documented and incorporated into an Inflow Design Flood study: Post-Wildfire Natural Hazards Risk Analysis in BC
The Post-Wildfire Natural Hazards Risk Analysis in BC handbook describes the process of assessing change following wildfire, together with an evaluation of downslope and downstream risks to life, property, and infrastructure, or "elements at risk."
BC MetPortal MetPortal is an online platform providing access to precipitation-frequency tools and data. It hosts a wide range of data on extreme precipitation, case studies and other information to help users make informed decisions on dam safety.

The following studies can be found on MetPortal:

Precipitation Frequency (PF) Quantiles
The Ministry of Forests, Lands, Natural Resource Operations and Rural Development (FLNRORD) completed a study to determine point values of precipitation frequency (PF) quantiles within and surrounding the province of BC. The PF values have been estimated to an annual exceedance probability (AEP) of 1 in 1,000,000 years to allow comparison with local determined PMP values.

Probable Maximum Precipitation (PMP)
The Ministry of FLNRORD completed a study to develop PMP guideline values. The PF data can be used to estimate the equivalent annual AEP of PMP for small (less than 50 km2) basins. Larger basins require use of an areal reduction factor (ARF) before using the PMP values in a hydrology model.
Pacific Climate Impacts Consortium (PCIC) The Pacific Climate Impacts Consortium (PCIC) data portal provides access to numerous datasets, information, and publications related to flood hydrology, extreme precipitation, and climate change in BC.
BC Hydro Application of the British Columbia MetPortal for Estimation of Probable Maximum Precipitation and Probable Maximum Flood for a Coastal Watershed
This paper developed by BC Hydro proposes an approach to process and apply this data for the estimation of the Probable Maximum Flood 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 using the MetPortal. The methodology is applied to estimate the PMF for the Cheakamus Basin north of Squamish in British Columbia.
CSA Group This Standards Research document provides a review of climate vulnerabilities, adaptation measures, and opportunities for growth in the Canadian dams context.
RTI and MGS Engineering Draft MetPortal Application Guidance for BC Freshwater Dams
The intent of the document is to:
  • Communicate the level of effort required to complete a suitable flood study commensurate with the failure consequence of the dam;
  • Discuss the two basic approaches to completing a study (i.e., deterministic and probabilistic);
  • Summarize basic concepts of watershed modelling;
  • Discuss the importance of utilizing numerous types of data/information when modeling flood processes, including rainfall magnitude, storm characteristics, temperature sequences, dew point temperatures, etc.; and
  • Provide options for assessing uncertainty of estimates, including climate change.