This layer represents the watershed areas that report to Water Survey of Canada (WSC) and United States Geological Survey (USGS) gauge stations that meet the following criteria for inclusion: at least 10 years or data (with 350 or more days of observations) above the low outlier threshold; less than 20% (by basin drainage area) regulation; a corresponding basin polygon dataset (either supplied or delineated) with a area <15% different than the basin area reported by WSC or USGS; full metadata coverage for the basin (e.g. mean annual precipitation, elevation, etc.); and 1-, 3-, 5-, and -10 day distribution fits that did not overlap for any Average Recurrence Interval’s (ARI) above 2 years. See Bulletin 2020-1-RFFA British Columbia Extreme Flood Project – Regional Flood Frequency Analysis – Technical development report and manual to complete a regional flood frequency analysis.

The BC Hydrologic Zones represent regions of similar climate and terrain resulting in somewhat homogeneous hydrology characteristics. The zones were defined previously by Obedkoff and others. This dataset has been extended into the neighbouring province, territories, and states for regional flood frequency analysis studies. See Bulletin 2020-1-RFFA British Columbia Extreme Flood Project – Regional Flood Frequency Analysis – Technical development report and manual to complete a regional flood frequency analysis.

This layer represents Water Survey of Canada (WSC) and United States Geological Survey (USGS) gauge stations that meet the following criteria for inclusion: at least 10 years or data (with 350 or more days of observations) above the low outlier threshold; less than 20% (by basin drainage area) regulation; a corresponding basin polygon dataset (either supplied or delineated) with a area <15% different than the basin area reported by WSC or USGS; full metadata coverage for the basin (e.g. mean annual precipitation, elevation, etc.); and 1-, 3-, 5-, and -10 day distribution fits that did not overlap for any Average Recurrence Interval’s (ARI) above 2 years. See Bulletin 2020-1-RFFA British Columbia Extreme Flood Project – Regional Flood Frequency Analysis – Technical development report and manual to complete a regional flood frequency analysis.