Irregular open channel property sheet

In this window you can enter and review data for open channels that:

are prismatic but have a shape other than trapezoidal, triangular or rectangular, or
do not have a regular cross-sectional shape, such as sections that occur with a natural stream or river.

Models of natural channels, or those with non-trapezoidal shapes, will consist of a number of irregular channels linked through nodes.

The sheet below is the one that is used with Lite and Full Unsteady hydraulic models. It only allows for one cross-section per channel.

For each channel link, you must enter:

the channel length,
Manning's n values for the left overbank (LOB) area or zone, the main channel and the right overbank (ROB) area,
a set of pairs of cross-section coordinates with the X values being horizontal distances or stations taken from a station or vertical datum to the left of the channel section and the Y values being the corresponding elevations (m),
two horizontal distances from the section’s datum indicating the locations of the left and right bank, used to define the zones where different roughness values apply,
contraction and expansion coefficients applied to allow for energy losses due to these causes. Values are typically 0.1 and 0.3., as shown in the following table, taken from the HEC.RAS Version 5.0 Hydraulic Reference Manual (2016), Chapter 3:

invert levels at the upstream and downstream ends of the channel.

To the right of the property sheet there are buttons allowing you to enter, delete and transfer cross-sections. A check box allows you to provide a horizontal roof for each cross-section.

In the pop-up menu that calls this box there is also the opportunity to display plots of cross-sections. This can be used in addition to the plot in the upper right corner of this sheet, to check the cross-sections for obvious errors.