Flood frequency statistics for streamgages and methods for estimating flood frequency statistics at ungaged sites in Alaska and conterminous basins in Canada are presented in U.S. Geological Survey Scientific Investigations Report 2016-5024. This report revised methods for obtaining basin characteristics and regional skew, and presents new streamflow magnitude and frequency statistics for gaged basins and new regression equations for estimating these statistics for ungaged basins.
Return to Water >> Alaska Streamflow Statistics
Peak-flow special conditions
Peak flows from selected peak-generating mechanisms can have a characteristic magnitude and frequency different from other peak flows. A table of selected special conditions affecting the magnitude of peak flows at USGS streamgages in Alaska is available in a data release (Curran, 2023).
Basin characteristics
Basin characteristics are physical and climatic features used as independent variables for estimating streamflow. Basin characteristics for an ungaged site that are substituted in the estimating equations should be determined by the same methods as those used to develop the equations. USGS SIR 2016-5024 uses two basin characteristics for estimating flood frequency:
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Drainage area (DRNAREA) is obtained from a drainage area boundary for the site in question. Drainage area delineations are based on the Watershed Boundary Dataset.
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Basin average mean annual precipitation for 1971–2000 from the PRISM climate dataset (PRECPRIS00) is obtained for areas in Alaska from Gibson (2009) (tip: no password is required when accessed from Internet Explorer) and for areas in Canada from PRISM Climate Group (2002).
Basin characteristics have been computed for selected streamgages and can be downloaded as a table from USGS SIR 2016-5024 Appendix A , also available as an ESRI geodatabase.

Regional skew areas
Flood frequency estimates for a streamgage are improved by using a weighted average of the station skew and a regional skew. USGS SIR 2016-5024 presents regional skew and standard error of the regional skew for two new regional skew areas (see figure 5, table 5, and table 6). Areas outside the regional skew areas are considered skew exclusion areas where station skew is used.
Statistics/equations
Flood frequency statistics for streamgages in Alaska and conterminous basins in Canada with at least 10 years of record through water year 2012 are shown in table form in USGS SIR 2016-5024 table 4 and can be obtained from a map view in StreamStats.
Tools for estimating flood frequency statistics are available in spreadsheet form in the USGS SIR 2016-5024 Applications Tool and in the USGS National Streamflow Statistics (NSS) program. For sites within Cook Inlet Basin, StreamStats provides tool for delineating a drainage area, computing basin characteristics, and computing the flood frequency estimation equations.
Below are other science projects associated with this project.
Alaska Streamflow Statistics
Flood Frequency Data Collection for Alaska and Conterminous Drainage Basins in Canada
Flow Duration and Low-Flow Frequency Studies in Alaska
Below are data or web applications associated with this project.
Selected Peak-Flow Special Conditions for USGS Streamgages in Alaska
Flood Frequency Data Collection, Alaska and Conterminous Basins in Canada
Streamgage Attributes, Basin Characteristics, and Seasonal Flow Regimes, Selected Streamgages in Alaska, 1914-2017
Estimating flood magnitude and frequency at gaged and ungaged sites on streams in Alaska and conterminous basins in Canada, based on data through water year 2012
Below are data or web applications associated with this project.
National Water Information System (NWIS) Mapper
The National Water Information System (NWIS) Mapper provides access to over 1.5 million sites contained in the USGS National Water Information System (NWIS), including sites where current and historical surface-water, groundwater, springs, and atmospheric data has been collected. Users can search by site type, data type, site number, or place.
Below are software products associated with this project.
- Overview
Flood frequency statistics for streamgages and methods for estimating flood frequency statistics at ungaged sites in Alaska and conterminous basins in Canada are presented in U.S. Geological Survey Scientific Investigations Report 2016-5024. This report revised methods for obtaining basin characteristics and regional skew, and presents new streamflow magnitude and frequency statistics for gaged basins and new regression equations for estimating these statistics for ungaged basins.
Return to Water >> Alaska Streamflow Statistics
Peak-flow special conditions
Peak flows from selected peak-generating mechanisms can have a characteristic magnitude and frequency different from other peak flows. A table of selected special conditions affecting the magnitude of peak flows at USGS streamgages in Alaska is available in a data release (Curran, 2023).
Basin characteristics
Basin characteristics are physical and climatic features used as independent variables for estimating streamflow. Basin characteristics for an ungaged site that are substituted in the estimating equations should be determined by the same methods as those used to develop the equations. USGS SIR 2016-5024 uses two basin characteristics for estimating flood frequency:
-
Drainage area (DRNAREA) is obtained from a drainage area boundary for the site in question. Drainage area delineations are based on the Watershed Boundary Dataset.
-
Basin average mean annual precipitation for 1971–2000 from the PRISM climate dataset (PRECPRIS00) is obtained for areas in Alaska from Gibson (2009) (tip: no password is required when accessed from Internet Explorer) and for areas in Canada from PRISM Climate Group (2002).
Basin characteristics have been computed for selected streamgages and can be downloaded as a table from USGS SIR 2016-5024 Appendix A , also available as an ESRI geodatabase.
Sources/Usage: Public Domain. Visit Media to see details.Regional skew areas for AK and conterminous basins in Canada. Regional skew areas
Flood frequency estimates for a streamgage are improved by using a weighted average of the station skew and a regional skew. USGS SIR 2016-5024 presents regional skew and standard error of the regional skew for two new regional skew areas (see figure 5, table 5, and table 6). Areas outside the regional skew areas are considered skew exclusion areas where station skew is used.
Statistics/equations
Flood frequency statistics for streamgages in Alaska and conterminous basins in Canada with at least 10 years of record through water year 2012 are shown in table form in USGS SIR 2016-5024 table 4 and can be obtained from a map view in StreamStats.
Tools for estimating flood frequency statistics are available in spreadsheet form in the USGS SIR 2016-5024 Applications Tool and in the USGS National Streamflow Statistics (NSS) program. For sites within Cook Inlet Basin, StreamStats provides tool for delineating a drainage area, computing basin characteristics, and computing the flood frequency estimation equations.
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- Science
Below are other science projects associated with this project.
Alaska Streamflow Statistics
The USGS conducts various studies of streamflow statistics for data collected at streamflow-gaging stations. Streamflow statistics for gaged streams and methods for estimating those statistics for ungaged streams are used by water resource planners and managers for designing infrastructure, managing floodplains, and protecting life, property, and aquatic resources. The most recent USGS studies of...Flood Frequency Data Collection for Alaska and Conterminous Drainage Basins in Canada
Estimates of the magnitude and frequency of floods are needed for engineering design of transportation and water-conveyance structures, flood-insurance studies, flood-plain management, and other water-resource purposes. In 2016, the U.S. Geological Survey estimated flood frequency and magnitude for selected streamgages in Alaska and conterminous basins in Canada and developed methods for...Flow Duration and Low-Flow Frequency Studies in Alaska
Flow duration and low-flow frequency statistics for streamgages and methods for estimating flow-duration and low-flow frequency statistics at ungaged sites in Alaska and conterminous basins in Canada are presented in U.S. Geological Survey Water Resources Investigations Report 2003-4114. - Data
Below are data or web applications associated with this project.
Selected Peak-Flow Special Conditions for USGS Streamgages in Alaska
This data package documents selected special conditions affecting the magnitude of peak flows at streamgages in Alaska. The data consist of a table of special conditions for selected peak flows and a table of data sources. This dataset resolves ambiguity introduced by historical variations in USGS National Water Information System (NWIS; https://doi.org/10.5066/F7P55KJN) peak-flow code assignmentFlood Frequency Data Collection, Alaska and Conterminous Basins in Canada
This data collection of U.S. Geological Survey data releases provides the source data and results of flood frequency analyses and annual exceedance probability estimation for selected observed floods in Alaska and conterminous basins in Canada. The data include streamgage information, PeakFQ input and output, flood frequency parameters, flood frequency estimates for selected annual exceedance probStreamgage Attributes, Basin Characteristics, and Seasonal Flow Regimes, Selected Streamgages in Alaska, 1914-2017
This data set contains selected information about U.S. Geological Survey (USGS) streamgages in Alaska that had at least 5 years of daily streamflow record through September 30, 2017. The goals for developing this dataset were to identify USGS streamgages that had at least 5 years of daily streamflow that responded mostly to seasonal meteorological inputs, that had a definable drainage basin above - Publications
Estimating flood magnitude and frequency at gaged and ungaged sites on streams in Alaska and conterminous basins in Canada, based on data through water year 2012
Estimates of the magnitude and frequency of floods are needed across Alaska for engineering design of transportation and water-conveyance structures, flood-insurance studies, flood-plain management, and other water-resource purposes. This report updates methods for estimating flood magnitude and frequency in Alaska and conterminous basins in Canada. Annual peak-flow data through water year 2012 weAuthorsJanet H. Curran, Nancy A. Barth, Andrea G. Veilleux, Robert T. Ourso - Web Tools
Below are data or web applications associated with this project.
National Water Information System (NWIS) Mapper
The National Water Information System (NWIS) Mapper provides access to over 1.5 million sites contained in the USGS National Water Information System (NWIS), including sites where current and historical surface-water, groundwater, springs, and atmospheric data has been collected. Users can search by site type, data type, site number, or place.
ByWater Resources Mission Area, Central Midwest Water Science Center, Colorado Water Science Center, Dakota Water Science Center, Maryland-Delaware-D.C. Water Science Center, New England Water Science Center, New Jersey Water Science Center, New Mexico Water Science Center, New York Water Science Center, South Atlantic Water Science Center (SAWSC), Upper Midwest Water Science Center, National Water Quality Laboratory - Software
Below are software products associated with this project.