Technical data

Chapter 3 Performing Hydrologic Studies

To add watershed and drainage data to your drawing

Steps

Use

to look up

1 Create an existing ground surface for the

proposed site.

Overview of Creating

Surfaces

2 Generate watershed data for the existing ground

surface model.

Create a Watershed Model

After Building the Surface

3 From the Terrain menu, choose Surface

Display ➤ Slope Arrows to draw arrows that

follow the slope of the existing surface.

4 From the Terrain menu, choose Surface

Utilities ➤ Water Drop to draw flow paths.

The Water Drop command traces the path of a

drop of water that lands on the point you pick in

the drawing to the point that it will outflow. This

can help you determine where the major outflow

points are and where you may need to add

culverts.

Draw Water Drop Paths

on the Current Surface

This data can help you visualize the slopes of a surface, where the

water will flow, and where the water will accumulate during a storm.

You can use this data to decide the best way of controlling the flow.

Now that you’ve visualized the runoff paths on your surface, you can

calculate the peak runoff flow for different storm events.

Using the Hydrology Calculators

Many of the features in the Hydrology menu use calculator-type

dialog boxes to solve for an unknown value. For each calculator, you

must enter the known values in the appropriate edit field for the

particular value, or use the corresponding Select button to pick the

value from the drawing or from another dialog box. You can select the

unknown value that you want to solve for from a popup list at the top

of the calculator. If you do not enter all values, then the calculation

will not be completed. An error message is displayed at the bottom of

the dialog box whenever you make an error entering data.