The purpose of the Quick-2 Mailing List is to provide up-to-date information about Quick-2 software, tutorials, and other related topics pertinent to the Federal Emergency Management Agency (FEMA) and the National Flood Insurance Program (NFIP).

This month we will determine if the flow of a circular channel can be contained in the channel or not. This exercise will be based on open flow channel conditions. For this exercise our depth of flooding must be less than the diameter of the channel, if it is not we will know that the channel can not handle the flow. We will take a look at a circular channel with varying discharges to determine if the flow will be contained in the channel. We will also see how Quick-2 responds when the flow is not contained in the channel. Two examples are provided below. In doing this, we will use Quick-2 to do the following:

  • Determine the BFE Using Normal Depth and Circular Channel Method
  • Run Multiple Analyses with Varying Discharges
  • View Cross Section Plots

The results of the survey are given below:

Cross-Section 1: Cross-Section 2:
Manning's n-value .015 .015
Slope (ft/ft) .0065 .0065
Diameter (in) 36 36
Discharge (cfs) 50 60

To Determine the BFE Using Quick-2 Normal Depth Method and Circular Channel:

  1. Create a new file and save it as a Quick-2 file type (.qk2)
  2. Click 'Method' and select 'Normal Depth' and 'Circular Channel'
    [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 of the channel
  6. Enter the Diameter of the channel
  7. Enter the Discharge

The cursor will now be in the 'Begin Calculation' box. The calculated depth of water through the channel is 2.8 feet. We know that the diameter of the channel is 3 feet so the flow will be contained in the channel.

You will next have to determine the depth for cross-section 2. Simply click on 'Cross Section' and change the number to 2. All the variables are the same with the exception of the discharge. Change the discharge to 60 cfs and then go to 'Begin Calculation'. When we try and calculate the depth we see a message in the 'Flow Type' box located in the lower right side of the screen that says Reduce Q. Quick-2 will not allow you to calculate a normal depth that is not contained in the channel. We know that when we receive this message, the flow would not be contained in the channel and therefore would not be a valid computation. If the depth exceeds the channel diameter, open channel flow no longer exists and this method is not applicable.

To view a cross-section plot choose what cross-section you want to view and click on 'View' and select "Xsec Plot' or click on the cross-section button in the upper right area of the screen. You can also view the rating curve on the same graph by clicking on the 'Curve Now!' button. To print the graph that you are viewing simply click on 'Print' and you can have a hard copy of the cross-sections to your property.

Next month we will look at how Quick-2 is used in the Letter of Map Amendment (LOMA) process.

View the archive page for all Flood Hazard Mapping listservs.

Last Modified: Tuesday, 26-Jun-2007 11:57:20 EDT