Alan Rea
Robert L. Tortortelli
Marvin A. Abbott
1997
Unknown
Generalized peak skew coefficients for Oklahoma, 19611990 base period.
1.0
map
OpenFile Report
97574
Reston, VA
U.S. Geological Survey
http://water.usgs.gov/lookup/getspatial?ofr97574_ok_skew
This digitalmap 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 WaterResources Investigations
Report 844358. The skew coefficients were used to develop
peakflow regression equations in the Tortorelli, 1997 report,
"Techniques for estimating peakstreamflow frequency for
unregulated streams and streams regulated by small floodwater
retarding structures in Oklahoma," U.S. Geological Survey
WaterResources Investigations Report 974202. 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 peakstreamflow frequency
in Oklahoma by Tortorelli (1997). The skew coefficients from this
data set were used to develop the peakflow 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 digitalmap 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 peakflow 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 peakstreamflow
frequency for unregulated streams and streams regulated by small
floodwater retarding structures in Oklahoma: U.S. Geological
Survey WaterResources Investigations Report 974202, 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 WaterResources Investigations
Report 844358, 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 Committeecompliant 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/INFOspecific 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.
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 1:500,000scale mylar draft map,
which was photoreduced 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 peakstreamflow 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
18882758747
(405)8437712
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 peakstreamflow
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 1:500,000scale mylar draft
used to make figure 11 in Tortorelli and Bergman (1985).
Registration tics were taken from latitudinal and longitudal
marks. The rootmeansquare error for ticmark 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 skewcoefficient 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
Semimajor_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
445 National Center
Reston
VA
20192
18882758747 (1888ASKUSGS)
http://answers.usgs.gov/cgibin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+ofr97574_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
Mapprojection 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
445 National Center
Reston
VA
20192
18882758747 (1888ASKUSGS)
http://answers.usgs.gov/cgibin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+ofr97574_ok_skew
FGDC Content Standards for Digital Geospatial Metadata
FGDCSTD0011998