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This month we will determine the channel capacity of a Triangular Channel. For this analysis we will determine the discharge (cfs) of a Triangular Channel using varying depths. We will run three cross sections to see how the change in depth affects the discharge. We will complete the exercise by looking at the rating curves, cross section plots, and the detailed input/output data. We will use Quick-2 to do the following:

  • Determine the Channel Capacity using the 'Triangular Channel' method
  • Run multiple analysis using different depths
  • View rating curves and cross section plots
Slope .0037 ft/ft
L Side Slope 3 (H:V)
R Side Slope 2 (H:V)
Manning's n .045
Depth 1 4.2
Depth 2 5.3
Depth 3 6.5

To Determine the Channel Capacity Using Quick-2 Triangular Channel Method:

  1. Create a new file and save it as a Quick-2 file type (.qk2)
  2. Click 'Method' and select 'Channel Capacity' and then 'Triangular'

    [Hit 'Enter' after each step below]

  3. Enter '1' for the cross-section number
  4. Enter the manning's n-value
  5. Enter the slope
  6. Enter the L Side Slope (H:V)
  7. Enter the R Side Slope (H:V)
  8. Enter the Depth

When all the data is entered, the 'Begin Calculation' button will have a box around the word 'Begin Calculation.' To compute the Discharge, either click on 'Begin Calculation' or hit enter.

The results are displayed on the right side of the screen in the 'Output' section. The computed Discharge (located in the Discharge box) is 138 cfs.

After we determine the discharge for cross section 1 we will enter in cross section 2. Simply go to the 'Cross Section' box and change the number to 2 and hit enter. Because all the data will remain the same except for the depth, simply change the depth to 5.3 feet and click on the 'Begin Calculation' button to display the discharge for cross section 2. The discharge for cross section 2 is 257 cfs.

Next to determine the discharge for cross section 3, go to the 'Cross Section' box and change the number to 3 and hit enter. Change the depth to 6.5 feet and click on 'Begin Calculation'. The discharge for cross section 3 is 442 cfs.

Next we will take a look at the Rating Curve and Cross Section Plot. Go to 'View' and 'X Sect Plot' to view the cross section. At the bottom of the graph click on 'Curve Now !' and the rating curve will be plotted on the same graph. With the rating curve and cross section plot on the same graph we get a good representation of what is going on at the site. The cross section plot also gives a very good representation of the shape of the triangular channel. It would also be beneficial to print a copy of this also, simply click on the 'Print' button at the bottom of the graph. We can also see the rating curve data in a word file. Go to 'View' and 'Rating Curve Data'. This will show each cross section and the rating curve of how the discharge is increasing with depth. To print this data go to 'File' and 'Print'. To finish, just Click 'File' then 'Close/Save'; and then close out any remaining windows.

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Last Modified: Monday, 25-Jun-2007 11:57:20 EDT