Limitations to the bottomless culvert scour analysis.
In order to use this method of analysis for a culvert, there must be a downstream control that will maintain flow depths
inside the culvert so that velocity decreases as scour increases. If there is no control downstream, then it is likely
that channel degradation will occur downstream, through and upstream of the culvert. If the user encounters this flow
condition in the culvert, the ABSCOUR bottomless culvert module should not be used to design the culvert since it does
not account for the effect of anticipated increases in the velocity of flow in the culvert.
Hydraulic flow conditions should be checked for several discharges to verify that the downstream controls are effective
for low and intermediate flows as well as the design flow.
For the flow conditions described above, including supercritical flow, the user is encouraged to consider one of the following options:
- Modify the bottomless culvert design; or construct downstream controls to minimize degradation and scour of the downstream channel.
Provide riprap to control scour and stabilize the culvert outlet, or provide riprap in the culvert barrel of adequate D50 size to resist
movement for design conditions.
- Select an alternative design