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 streamflow statistics for Alaska are presented in reports on flood frequency, flow duration, low-flow frequency, and streamflow record extension.
Return to Water
Methods for accessing data and estimating streamflow statistics for Alaska are provided in USGS reports and, for selected locations, in the online StreamStats tool. These studies use data from USGS streamflow data-collection stations, available online at NWISWeb.
Flood Frequency Studies
Flood frequency analysis uses a series of annual peak-streamflow, or flood, data recorded for a stream to develop a statistical expression of flood probability for that stream, such as the 1-percent chance flood (sometimes called the 100-yr flood). Regression equations relating flood frequency statistics for a group of gaged streams to physical or climatic characteristics of their respective drainage areas provide a tool for estimating flood frequency statistics at ungaged areas. The USGS most recently revised flood frequency regression equations for Alaska and conterminous basins in Canada in 2016.
Flow Duration and Low-Flow Frequency Studies
Flow duration statistics, such as the 98-percent duration flow, describe the daily mean discharge in a stream that is exceeded a given percentage of the time. Low-flow frequency statistics, such as the 7-day, 2-yr low flow, refer to the discharge that occurs on a certain number of consecutive days that is associated with a certain exceedance probability. Regression equations relating these streamflow statistics for a group of gaged streams to physical or climatic characteristics of their respective drainage areas provide a tool for estimating the streamflow statistics at ungaged areas. The USGS has developed selected flow-duration and low-flow frequency regression equations for Alaska and conterminous basins in Canada.
Cook Inlet Basin StreamStats
StreamStats is a web-based application that facilitates access to data and computation tools and streamlines estimation of streamflow statistics. StreamStats is presently available in Alaska only for the Cook Inlet Basin. In addition to providing previously computed information for a streamgage location, Cook Inlet Basin StreamStats automates delineation of a drainage basin for a user-selected location, determination of the drainage area and mean annual precipitation, and computation of flood frequency estimates using those basin characteristics. The development of the Cook Inlet Basin StreamStats application is described in the most recent USGS Alaska flood-frequency report, U.S. Geological Survey Scientific Investigations Report 2016-5024.
Streamflow Record Extension
Daily streamflow values for a short-record streamgage can be estimated from data for a longer-record index streamgage when the daily values for the overlapping period are closely correlated. Streamflow record extension creates a continuous string of daily values at the short-record streamgage for the period of record of the longer-record streamgage.
The USGS has approved streamflow records extension data for selected gaged streams. The data, methods of analysis, and accuracy of the estimated discharges are available in the accompanying reports.
| Stream | Publication |
|---|---|
| Selected gaged streams in the Susitna River Basin | USGS Scientific Investigations Report 2012-5210 |
| North Fork and Middle Fork Fortymile Rivers, through water year 2019 | USGS Scientific Investigations Report 2020-5003 |
| North Fork and Middle Fork Fortymile Rivers, through water year 2020 | USGS Scientific Investigations Report 2021-5014 |
Below are related science to this project.
Flood Frequency Studies in Alaska
Flow Duration and Low-Flow Frequency Studies in Alaska
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 streamflow statistics for Alaska are presented in reports on flood frequency, flow duration, low-flow frequency, and streamflow record extension.
Return to Water
Methods for accessing data and estimating streamflow statistics for Alaska are provided in USGS reports and, for selected locations, in the online StreamStats tool. These studies use data from USGS streamflow data-collection stations, available online at NWISWeb.
Flood Frequency Studies
Flood frequency analysis uses a series of annual peak-streamflow, or flood, data recorded for a stream to develop a statistical expression of flood probability for that stream, such as the 1-percent chance flood (sometimes called the 100-yr flood). Regression equations relating flood frequency statistics for a group of gaged streams to physical or climatic characteristics of their respective drainage areas provide a tool for estimating flood frequency statistics at ungaged areas. The USGS most recently revised flood frequency regression equations for Alaska and conterminous basins in Canada in 2016.
Flow Duration and Low-Flow Frequency Studies
Flow duration statistics, such as the 98-percent duration flow, describe the daily mean discharge in a stream that is exceeded a given percentage of the time. Low-flow frequency statistics, such as the 7-day, 2-yr low flow, refer to the discharge that occurs on a certain number of consecutive days that is associated with a certain exceedance probability. Regression equations relating these streamflow statistics for a group of gaged streams to physical or climatic characteristics of their respective drainage areas provide a tool for estimating the streamflow statistics at ungaged areas. The USGS has developed selected flow-duration and low-flow frequency regression equations for Alaska and conterminous basins in Canada.
Cook Inlet Basin StreamStats
StreamStats is a web-based application that facilitates access to data and computation tools and streamlines estimation of streamflow statistics. StreamStats is presently available in Alaska only for the Cook Inlet Basin. In addition to providing previously computed information for a streamgage location, Cook Inlet Basin StreamStats automates delineation of a drainage basin for a user-selected location, determination of the drainage area and mean annual precipitation, and computation of flood frequency estimates using those basin characteristics. The development of the Cook Inlet Basin StreamStats application is described in the most recent USGS Alaska flood-frequency report, U.S. Geological Survey Scientific Investigations Report 2016-5024.
Streamflow Record Extension
Daily streamflow values for a short-record streamgage can be estimated from data for a longer-record index streamgage when the daily values for the overlapping period are closely correlated. Streamflow record extension creates a continuous string of daily values at the short-record streamgage for the period of record of the longer-record streamgage.
The USGS has approved streamflow records extension data for selected gaged streams. The data, methods of analysis, and accuracy of the estimated discharges are available in the accompanying reports.
| Stream | Publication |
|---|---|
| Selected gaged streams in the Susitna River Basin | USGS Scientific Investigations Report 2012-5210 |
| North Fork and Middle Fork Fortymile Rivers, through water year 2019 | USGS Scientific Investigations Report 2020-5003 |
| North Fork and Middle Fork Fortymile Rivers, through water year 2020 | USGS Scientific Investigations Report 2021-5014 |
Below are related science to this project.
Flood Frequency Studies in Alaska