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Unformatted text preview: The default is to have equal
conveyance reduction turned on.
The second item under global information is the Left bank offset and the
Right bank offset. The left and right offsets are used to establish a buffer
zone around the main channel for further limiting the amount of the
encroachments. For example, if a user established a right offset of 5 feet and
a left offset of 10 feet, the model will limit all encroachments to 5 feet from
the right bank station and 10 feet from the left bank station. The default is to
have no right or left offset, this will allow the encroachments to go up to the
main channel bank stations, if necessary. 10-4 Chapter 10 Performing a Floodway Encroachment Analysis River, Reach and River Station Selection Boxes. The next piece of data for
the user to select is the river and reach in which to enter encroachment data.
The user is limited to seeing one reach at a time on the encroachment data
editor. Once a reach is selected, the user can then enter a Starting and
Ending River Station to work on. By default, the program selects all the
sections in the reach. The user can change this to any range of cross sections
within the reach.
Profile. Next, the user should select a profile number to work on. Profiles
are limited to 2 through the maximum number set in the currently opened
flow data (e.g., 2 through 4, if the user has set 4 profiles in the flow data
editor). The user can not set encroachments for profile 1.
Method and Target Values. The next step is to enter the desired
encroachment method to be used for the currently selected profile. Once a
method is selected, the data entry boxes that corresponds to that method will
show up below the method selection box. Some of the methods require only
one piece of data, while others require two. The user should then enter the
required information that corresponds to the method that they have selected.
For example, if the user selects encroachment method 4, only one piece of
information is required, the target change in water surface elevation. The
available encroachment methods in HEC-RAS are:
Method 1 Method 2 Method 3 Method 4 Method 5 - User enters right and left encroachment station
User enters a fixed top width
User specifies the percent reduction in conveyance
User specifies a target water surface increase
User specifies target water surface increase and
maximum change in energy Set Selected Range. Once the encroachment method is selected, and its
corresponding data are entered, the user should press the Set Selected Range
button. Pressing this button will fill in the table below with the selected range
of river stations; the selected method; and the corresponding data for the
method. Note that, if the selected method only has one data item, that
method’s data will go under the Value 1 column of the table. If the selected
method has two data items, the first goes into the Value 1 column and the
second goes into the Value 2 column. Once the data is put into the table, the
user can change the method and corresponding data values directly from the
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- Spring '13