How do I measure the gradient of a winding culvert?

[pilesmakesmiles]

We are working on a drainage investigation, a significant part of which involves calculating the flow capacity of a 100m long culvert beneath a road and some houses to see if it is likely to surcharge.

We want to determine the gradient of the culvert to verify someone else's guesstimate which seems quite steep compared to the fall of the land.

In an ideal world we would measure the level at the upstream end and the downstream end, the distance between the two and get a slope. Unfortunately there is no access to the upstream end.

We could start at the downstream end and measure the level from inside the culvert. Unfortunately the culvert is approximately 1m x 1m in section and had a bend every 5-10m so this would be very time consuming. There are no intermediate access chambers on the culvert.


Can anyone suggest any methods for working out the gradient of the culvert to a reasonable degree of accuracy?

 

[3feethighandrising]

Isn't there an easement on his property for this culvert? If so you don't need his permission to enter and bring equipment into the easement area. Have someone pull up the title to look for the storm easement. If an easement exists, have title with you when you inspect show it to the owner and call the police if he bothers or denies you entry.

Also inform them that any structures built in this easement maybe removed at the cost of the owner, if so directed by the storm utility.