Ak_ff_pl is a polygon coverage showing streamflow analysis regions in Alaska and conterminous basins in Canada. These streamflow analysis regions were developed as part of a flow-duration and flood frequency study completed in 2003 (Wiley and Curran, 2003; Curran and others, 2003) that updates and supplements a flood frequency study by Jones and Fahl (1994). The state and conterminous basins in Canada were divided into seven streamflow analysis regions having similar hydrologic characteristics for the purpose of developing regional equations for estimating selected streamflow statistics, including high-duration flow, low-duration flow, low-flow frequency, and peak-flow frequency.
Streamflow analysis region boundaries may be used to determine the region or regions containing a gaged or ungaged site’s drainage area in order to selected the appropriate regional equations from Wiley and Curran (2003) and Curran and others (2003). Procedures are provided in each report for estimating selected streamflow statistics for sites with drainage areas in one or more regions. Computations for sites with watersheds in more than one region are based on the drainage area, in square miles, of the watershed within each region. Areas outside the polygons are not included in the study area (primarily the western Aleutian islands and selected offshore islands for which no data exist).
Procedures_Used These streamflow analysis regions for Alaska and conterminous basins in Canada were created from existing hydrologic region coverages by scanning a a paper map showing previously developed flood frequency regions (Jones and Fahl, 1994) as a high quality tiff, georeferencing it to the Albers projection, and overlaying it with published digital hydrologic unit maps of Alaska (Lamke and others, 1995) and Canada (Canada Watershed Maps,1972). Hydrologic unit boundaries most closely approximating the 1994 Jones and Fahl region boundaries (and/or edits made to those boundaries by the present authors) were selected and merged to create the present region boundaries. Canadian hydrologic boundaries were adjusted slightly when needed to match Alaska boundaries. In general, the polygon boundaries follow the coastline, except along the southern portion of Alaska where on-screen digitizing was used to encompass offshore islands. The Hydrologic unit codes for the State of Alaska coverage is published at a 1:250,000 scale. The Watersheds of Canada coverages are published at a 1:2,000,000 scale.
Other_References_Cited: Wiley, Jeffrey B., and Curran, Janet H., 2003, Estimating annual high-flow statistics and monthly and seasonal low-flow statistics for ungaged streams in Alaska and conterminous basins in Canada: U.S. Geological Survey Water-Resources Investigations Report 03-4114. Lamke, Robert D., Brabets, Timothy P., and McIntire, Jacqueline A., 1995, Hydrologic unit codes for the State of Alaska: U.S. Geological Survey digital coverage, <http://agdc.usgs.gov/data/usgs/water> Jones, Stanley H., and Fahl, Charles B., 1994, Magnitude and frequency of floods in Alaska and conterminous basins of Canada: U.S. Geological Survey Water-Resources Investigations Report 93-4179, 122 p., 2 plates. Government of Canada, 1972, Canada Watersheds Maps: Government of Canada digital coverage, <http://geogratis.cgdi.gc.ca/download/watrshed>
AK_FF_PL.PAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 AK_FF_PL# 4 5 B -
13 AK_FF_PL-ID 4 5 B -
17 ID 8 16 F 3
Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data.
The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.