Estimating Roughness Coefficients
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Use of this Search Engine :: Computational Tools ::
USE OF THIS SEARCH ENGINE
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Presentation and Comparison of Selected Streams :: Entering the range of n values :: Searching
by use of maps :: Addition of data to the database ::
The website essentially has two functions: (1) it allows the user to campare
data from a searchable database, and (2) it allows the user to interactively
enter variables into a variety of hydraulic equations that solve for the unknown
variable in the equation.
Presentation and Comparison of Selected Streams
The database can be accessed via the web page in several different ways. The
user can query the database by entering the range of
n values, or by
searching regionally by use of point and click maps. The results of the query
can then be presented and compared to a stream for which the user is attempting
to determine the roughness coefficient.
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Entering the range of n value
The user can specify the range of
n value of interest. A list of the
available data matching the range, or in the case that no available data are
available in the specified range, the data closest to the entered range, will be
listed in order of the best match. The list provides the five best matches from
the data base, and includes the site name, location, and "Match %". The "Match
%" is 100 percent if the
n value of the site is in the range specified by
the user, and decreases as the
n value of the site gets further away from
the specified range. The user can click on the "continue" button to continue the
list, which will eventually cycle through all of the data in the database.
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Searching by use of maps
The user can point and click on different States in the United States to
search the database. If the user clicks on a State, for which there is data in
the database, a list is produced which begins with data from that State. The
list then provides data from other States in order of closest proximity. The
"Match %" is 100 percent if the data are in the specified State, and decreases
by approximately 5% every State away. There is also a button available on the
main map page for data from outside of the continental U.S.
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Addition of data to the data base
The website will be maintained by the USGS, Illinois District. A download
button is also available on the website for users who wish to burn their own
CD-ROM for use in the field. The user can download updated versions as they deem
necessary. If you or your organization have additional data which could be added
to the data base, or if errors are found in the data, please contact
David Soong or
Teresa Halfar at the USGS.
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COMPUTATIONAL TOOLS
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Calculations using hydraulic and/or geometric data :: Entering channel characteristics ::
The web page also has an interactive utility that allows the user to enter
variables into a variety of hydraulic equations. Most of these equations were
developed for specific stream characteristics, so a more in-depth knowledge of
the references that each of the equations comes from could be helpful to the
user.
Calculations using hydraulic and/or geometric data
For any of the variety of equations listed, the user can enter known
hydraulic and geometric data in the appropriate fields and click the "Calculate"
button to determine the unknown value. Then, if the user wishes to compare the
calculated value to sites with the same or similar values, they can click on the
"Similar
n values" button. This action will automatically insert the
calculated
n value into both the maximum and minimum fields for the range
of
n. Clicking on the "Next" button will take the user to the database.
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Entering channel characteristics
The user can estimate the Manning's
n value for a given stream by
using Cowan's Method. The interface is very user friendly and the user simply
has to click on the characteristics of a stream to fill in the fields needed for
the
n value calculation. Clicking the button next to the description of
any given range for a stream characteristic parameter will automatically insert
the median for that range into the appropriate field. If the user wishes to
increase or decrease that value, he or she must go into the appropriate field
and manually change it.
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U.S. Department of the Interior |
U.S. Geological Survey