Average Flow Depth at Datum Point Inside Culvert
The datum point is a point inside the culvert to be selected by the user.
The datum point is selected to represent an average flow depth inside the culvert.
The following guidance pertains to selection of the datum point.
- For a short culvert, similar to a bridge, select the datum point at the culvert outlet.
- For a long culvert, select the datum point downstream of the entrance at least 2 culvert widths in order to be at a point where the flow is contracted.
- For a long culvert with subcritical flow and a tailwater above critical depth controlled by the downstream channel, select the normal depth in the culvert.
However, for a very high tailwater that submerges the culvert outlet, the flow depth is likely to be closer to the culvert height H. (The flow depth selected should not exceed the value of H)
- For a long culvert with subcritical flow in the barrel but critical flow at the outlet, further study needs to be made before calculating scour with this program (See Limitations)
- For a long culvert with supercritical flow in the barrel further study needs to be made before calculating scour with this program (See Limitations)