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.

This ArcGIS Online application displays the hydrometric stations and accompanying drainage areas analyzed as part of Bulletin 2020-1-RFFA described below. A frequency analysis was conducted on Annual Maximum Series (AMS) streamflow data collected at Water Survey of Canada (WSC) and United States Geological Survey (USGS) hydrometric gauge stations that met the following criteria for inclusion in the Bulletin 2020-1-RFFA study: 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 an 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. The analysis was conducted by Northwest Hydraulic Consultants and RTI International Inc. for the Water Management Branch of FLNRORD. The geographic area of the dataset is shown in Bulletin 2020-1-RFFA and consists of all of British Columbia and selected watersheds around the perimeter of the province. There are 3 datasets within this project consisting of: • Hydrometric station locations of the stations that were analyzed as part of the study. • The drainage areas of the respective hydrometric stations that were analyzed. • The BC Hydrologic Zones that were extended outside of BC.

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.

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.

The annual maximum and minimum daily data are the maximum and minimum daily mean values for a given year.

The daily mean is the average of all unit values for a given day.

The monthly mean is the average of daily mean values for a given month.

Historical hydrometric data are standardized water resource data and information. They are collected, interpreted and disseminated by the National Hydrological Services (NHS) in partnership with the provinces, territories and other agencies through the National Hydrometric Program. These data sets include daily mean, monthly mean, annual maximum and minimum daily mean and instantaneous peak water level and discharge information for over 2700 active and 5100 discontinued hydrometric monitoring stations across Canada.

The annual maximum and minimum instantaneous data are the maximum and minimum instantaneous values for a given year.