2.0

Calculating Culvert Size and Shape
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3 Click in the first row to start entering the overtop flow values for this culvert
calculation.
4 In the Length column, type a length for the roadway crest. This is the length of
the mid-section, at the center of the sag curve.
You can also click Length and specify the length by selecting an object or points
on the drawing. After you click Length, the Culvert Weir Editor dialog box
closes temporarily and you are prompted to select the first point. Continue
selecting points as you are prompted by moving the cursor crosshairs and
clicking the left mouse button. After you finish picking points, press the right
mouse button.
The Culvert Weir Editor dialog box displays and the value of the length you
selected displays in the Length text box.
5 In the Elevation column, type an elevation for the roadway crest at the sag
curve.
You can also click Elevation and specify the elevation by selecting a point on
the drawing. After you click Elevation, the Culvert Weir Editor dialog box closes
temporarily and you are prompted to select a point. Move the cursor crosshairs
to the point you want to select and click the left mouse button.
6 In the Broad Crested Weir Coefficient column, type a coefficient applicable to a
broad crested weir. Weir coefficients are usually between 2.5 and 3.3.
7 Define the next section using the same methods described above. For the
length, enter the combined length of the sections to the left and right of the
mid-section. For more information, see the preceding illustration on
overtopping in the introduction of this topic.
8 Click OK to return to the Culvert Design dialog box.
Displaying a Performance Curve for a Culvert
In the Culvert Design dialog box, there is a P Curve button. Click this button to
calculate and display the performance curve for the culvert on a graph. You can
adjust the settings in the Performance Curve Display dialog box.
NOTE
The Minimum Flow, Maximum Flow, and Flow Increment values used to
calculate the P-curve are determined in the Culvert Settings dialog box.
To display a performance curve for a culvert
1 In the Culvert Design dialog box, click P-Curve to display the Performance
Curve Display dialog box.
2 Click Settings to display the Graph Settings, such as line colors and scale.
3 Click Plot to change the settings for this plot.
4 Click Output to output the depth versus flow data to a text or .wk1 file.
5 Click OK to return to the Culvert Design dialog box.