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#           Flood Frequency Studies in Alaska      

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      By Alaska Science Center      December 1, 2023    

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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.

View Media Details

#####  

#### 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.

### Study Area

### Contacts

#### Janet H Curran

##### Hydrologist

Alaska Science Center

jcurran@usgs.gov

907-786-7128

### Explore Search

                      - Floods
                      - Streamflow Statistics
                      - Alaska Streamflow Statistics
                      - Water

View All **

Below are other science projects associated with this project.

link

December 1, 2023

####                 Alaska Streamflow Statistics              

Alaska Science Center

link

December 1, 2023

####   Alaska Streamflow Statistics

Learn More

link

March 17, 2022

####                 Flood Frequency Data Collection for Alaska and Conterminous Drainage Basins in Canada              

Alaska Science Center

link

March 17, 2022

####   Flood Frequency Data Collection for Alaska and Conterminous Drainage Basins in Canada

Learn More

link

May 18, 2018

####                 Flow Duration and Low-Flow Frequency Studies in Alaska              

Alaska Science Center

link

May 18, 2018

####   Flow Duration and Low-Flow Frequency Studies in Alaska

Learn More

Below are data or web applications associated with this project.

November 27, 2023

####                 Selected Peak-Flow Special Conditions for USGS Streamgages in Alaska              

Alaska Science Center

March 22, 2022

####                 Flood Frequency Data Collection, Alaska and Conterminous Basins in Canada              

Alaska Science Center

November 30, 2020

####                 Streamgage Attributes, Basin Characteristics, and Seasonal Flow Regimes, Selected Streamgages in Alaska, 1914-2017              

Alaska Science Center

March 16, 2016

####                 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              

Ecosystems Mission Area, Alaska Science Center, StreamStats

Below are data or web applications associated with this project.

March 4, 2019

####                 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.

Water 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

Below are software products associated with this project.

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.

View Media Details

#####  

#### 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.

### Study Area

### Contacts

#### Janet H Curran

##### Hydrologist

Alaska Science Center

jcurran@usgs.gov

907-786-7128

### Explore Search

                      - Floods
                      - Streamflow Statistics
                      - Alaska Streamflow Statistics
                      - Water

View All **

Below are other science projects associated with this project.

link

December 1, 2023

####                 Alaska Streamflow Statistics              

Alaska Science Center

link

December 1, 2023

####   Alaska Streamflow Statistics

Learn More

link

March 17, 2022

####                 Flood Frequency Data Collection for Alaska and Conterminous Drainage Basins in Canada              

Alaska Science Center

link

March 17, 2022

####   Flood Frequency Data Collection for Alaska and Conterminous Drainage Basins in Canada

Learn More

link

May 18, 2018

####                 Flow Duration and Low-Flow Frequency Studies in Alaska              

Alaska Science Center

link

May 18, 2018

####   Flow Duration and Low-Flow Frequency Studies in Alaska

Learn More

Below are data or web applications associated with this project.

November 27, 2023

####                 Selected Peak-Flow Special Conditions for USGS Streamgages in Alaska              

Alaska Science Center

March 22, 2022

####                 Flood Frequency Data Collection, Alaska and Conterminous Basins in Canada              

Alaska Science Center

November 30, 2020

####                 Streamgage Attributes, Basin Characteristics, and Seasonal Flow Regimes, Selected Streamgages in Alaska, 1914-2017              

Alaska Science Center

March 16, 2016

####                 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              

Ecosystems Mission Area, Alaska Science Center, StreamStats

Below are data or web applications associated with this project.

March 4, 2019

####                 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.

Water 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

Below are software products associated with this project.