Alan Rea Robert L. Tortortelli Marvin A. Abbott 1997 Unknown 1.0 map Open-File Report 97-574 Oklahoma City U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?ofr97-574_ok_skew This digital-map data set consists of a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 of the Tortorelli and Bergman, 1985 report, "Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma," U.S. Geological Survey Water-Resources Investigations Report 84-4358. The skew coefficients were used to develop peak-flow regression equations in the Tortorelli, 1997 report, "Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma," U.S. Geological Survey Water-Resources Investigations Report 97-4202. Only skew coefficient values within Oklahoma are intended for use with the regression equations. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. This data set was used for estimation of peak-streamflow frequency in Oklahoma by Tortorelli (1997). The skew coefficients from this data set were used to develop the peak-flow regression equations, and should be used to estimate peak flows in Oklahoma using the regression equations in Tortorelli (1997). This data set includes values outside Oklahoma that were used at selected stations for regression analyses by Tortorelli (1997). The regression equations and this data set are intended for use only for sites within Oklahoma. This digital-map data set consists of a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 in Tortorelli and Bergman (1985). The skew coefficients were used to develop peak-flow regression equations in Tortorelli (1997). Only skew coefficient values within Oklahoma are intended for use with the regression equations. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. Reviews_Applied_to_Data-- This electronic report was subjected to the same review standard that applies to all U.S. Geological Survey reports. Reviewers were asked to check the topological consistency, tolerances, attribute frequencies and statistics, projection, and geographic extent. Reviewers were given digital data sets and paper plots for checking against the source maps. The reviewers were asked to check the metadata and accompanying files for completeness and accuracy. Related_Spatial_and_Tabular_Data_Sets-- This data set is one of two digital map data sets being published for this report. The two data sets are: skewgrid - generalized peak streamflow skew coefficients maprecip - mean annual precipitation These data sets were used in regression analyses by Tortorelli (1997), and are being published so the data sets may be used to apply the regression equations to estimate peak streamflow frequencies. Other_References_Cited-- Environmental Systems Research Institute, Inc. (ESRI), 1995, ARC/INFO Command Reference: Redlands, CA. Tortorelli, R.L., 1997, Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma: U.S. Geological Survey Water-Resources Investigations Report 97-4202, 39 p. Tortorelli, R.L., and Bergman, D.L., 1985, Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma: U.S. Geological Survey Water-Resources Investigations Report 84-4358, 85 p. Notes-- Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this data set has 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 and related materials. 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. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, this metadata file was developed using the DOCUMENT program of ARC/INFO. Therefore, this metadata file may include some ARC/INFO-specific terminology. Data_Set_Credit-- The U.S. Geological Survey compiled this data set and the associated metadata in cooperation with the Oklahoma Department of Transportation. Vertical_Coordinate_System_Definition-- minimum -50 maximum 50 1985 Publication date of original report, Tortorelli and Bergman, 1985. Complete None planned -102.9933 -93.7089 38.0334 33.4770 None floods peak discharge design floods frequency analysis small watersheds regulated flow natural flow regression analysis, flood recurrence interval surface runoff storm runoff generalized skew map floodwater retarding structures ungaged watersheds inlandWaters None This data set was digitized from a 1:500,000-scale mylar draft map, which was photo-reduced and published by Tortorelli and Bergman (1985) at a scale of 1:2,500,000. The skew coefficients are generalized, and, therefore, may not be representative of individual station skew coefficients. Although skew coefficients from some stations outside Oklahoma were used to develop the generalized skew map by Tortorelli and Bergman (1985), the skew values are intended for use to develop peak-streamflow frequency curves for gaged sites only within Oklahoma. Alan Rea U.S. Geological Survey Hydrologist mailing address

202 NW 66th St., Bldg. 7

Oklahoma City Oklahoma 73116 United States of America 1-888-275-8747 (405)843-7712 ahrea@usgs.gov Please use email. Operating System-- UNIX, ARC/INFO Version 7.0.3,,(Mon Mar 13 22:21:55 PST 1995) Not available This data set includes values outside Oklahoma that were used at selected gaging stations outside Oklahoma to develop peak-streamflow frequency curves by Tortorelli (1997). This data set is intended for use only for sites within Oklahoma. Lines of equal average skew coefficient were digitized from the original 1:500,000-scale mylar draft used to make figure 11 in Tortorelli and Bergman (1985). Registration tics were taken from latitudinal and longitudal marks. The root-mean-square error for tic-mark registration was 0.009 inches. A line was added forming a loop on the -0.3 line in the northwest, to correctly represent the depression in the skew-coefficient surface. The map was digitized by Marvin Abbott. 19970304 The lines of equal average skew coefficient were projected from Lambert Conformal Conic map projection to Albers Equal Area, using standard parallels selected for Oklahoma, and the North American Datum of 1983 (NAD83) for the horizontal datum. Projection was done by Alan Rea. 19970430 The lines of equal average skew coefficient were processed into a grid using TOPOGRID, a module of ARC/INFO (ESRI, 1995), revision 7.0.3. An output cell size of 1,000 meters was used. The tolerances used were: 0.001 for root mean square residual, 0.05 for "tol1", and 0.1 for "tol2". TOPOGRID processing was done by Alan Rea. 19970512 To save disk space, the values in the grid were multiplied by 100 and rounded to integers with two significant digits. For example, a skew coefficient of -0.215 is represented in this data set as -22. To correct for data values extrapolated by TOPOGRID, all values larger than 50 (skew coefficient of 0.5) were changed to 50, and all values smaller than -50 were changed to -50. Values smaller than -20 (skew coefficient of -0.2) in southwestern Oklahoma were changed to -20. This processing step was done by Alan Rea. 19970711 Raster Grid Cell 502 841 Albers Conical Equal Area 34 36.5 -98 33 0.0 0.0 coordinate pair 1000.000 1000.000 meters North American Datum of 1983 Semi-major_Axis UNKNOWN SKEWGRID.VAT Grid value attribute table Tortorelli and Bergman, 1985 VALUE Generalized peak streamflow skew coefficient, multiplied by 100 Tortorelli and Bergman, 1985 Integer n/a n/a COUNT Number of GRID cells of a VALUE Computed Integer n/a n/a SKEWGRID.STA Statistics table GRID - Statistics table GRID - n/a n/a MIN Minimum GRID cell VALUE Computed Real number n/a n/a MAX Maximum GRID cell VALUE Computed Real number n/a n/a MEAN Mean GRID cell VALUE Computed Real number n/a n/a STDV Standard Deviation of GRID cell VALUEs Computed Positive real number n/a n/a The values stored in the grid cells equal the skew coefficients multiplied by 100 and rounded to two significant digits. For example, a skew coefficient of -0.215 is represented in this data set as -22. U.S. Geological Survey Ask USGS - Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+ofr97-574_ok_skew Although this data set has 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 and related materials. 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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Other Generalized peak skew coefficients ASCII grid, multiplied by 100 and rounded to two significant digits zipped 1 http://water.usgs.gov/GIS/dsdl/OK/skewgrid.gz Other Map-projection parameters for the peak skew coefficients data set 1 http://water.usgs.gov/GIS/dsdl/OK/skewgrid.prj None. This dataset is provided by USGS as a public service. 20041108 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+ofr97-574_ok_skew FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998