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Table Of Contents
Chapter 5 Working with Hydrology Commands
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Specifying the Shallow Flow
Shallow flow is water flowing in natural drainage depressions and swales, and
usually begins after a maximum of 300 feet of sheet flow. The average velocity
of shallow concentrated flow is determined by watershed slope and channel
material (paved or unpaved). Typical areas where you have shallow flow are in
swales between houses and the gutter section of a roadway.
To calculate shallow flow, you need the following information: flow length;
average slope; and a determination of whether the surface is paved or unpaved.
The Shallow Flow Time Calculator dialog box is available from the following
dialog boxes:
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Time of Concentration Calculator
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Time of Travel Calculator
To specify the shallow flow
1 In the Shallow Flow Time Calculator dialog box, type a description for the
shallow concentrated flow segment in the Description box.
2 Under Surface, select the appropriate surface condition: Paved or Unpaved.
3 In the Flow Length box, type the flow length of the shallow watercourse in feet.
You can also click Select to specify the length by selecting either an object or
points in the drawing.
4 In the Watercourse Slope box, type the slope of the shallow concentrated
watercourse. You can also click Select to specify the slope by selecting contours
on the drawing.
When you specify all three values in the dialog box, the following calculations
are displayed:
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Average Velocity: The calculated average velocity of the shallow
concentrated flow.
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Shallow Flow Time: The calculated shallow concentrated flow time. When
you click OK to return to the Time of Concentration calculator, this value is
inserted into the Shallow box.