HOW BIGA ?

[schmism]

the reason why culvert sizes change over time is because the amount of water the ditch carries changes over time. usually it carries more... not less..

why?

there is this thing called "time of concentration". its basicly how long it takes the water to flow off the ground and "into" the ditch.

as you devolope more land, convert more land from woods to "cleared property" the water runs off faster. SO

water USED to run into the ditch at a rate of X (cfs) the ditch (and culverts) were designed to carry the water away at X rate.

Now as develompent occures the water runs off quicker.. now you have water entering the ditch at 2X but the ditch can only carry it away at X. then you have issues.... (this is why major subdivsions are required to have retention ponds... a place to collect the water at 2x and allow it out into the "old" ditch at X rate... so durring times of high rainfall, it fills up quick, and slowly drains out)

so the culvert sized was increased and some time in the future they will come out and re-dig the ditches.

again most drainage calcs use a rain fall intenisty # (50 year rain etc) so that number will also change as they re-calc those numbers based on the last 50 or 100 years vs the 50 year number that was used in 1960.

so yes the ditch may have lived there for 80 years, but the engineering behind the size of the ditch changes over time based on a WHOLE lot of things. (not to mention arbitray changes in design specs like min slopes, etc)


as for who do you ask? your local DOT does not maintain all roads/ditches. Those in a city or under "county" maintaince do not fall into the DOT supervision and therefore the DOT engineer is likely to give you 'Thats not my problem" kind of answer ( in other words "Check with the county/city people, i dont have that information")

 

[LBrown59]

So the culvert size was increased and some time in the future they will come out and re-dig the ditches.

The last thing this ditch needs is widened or deepened.
Seems to me it shouldn't take a 60'' deep by 60 '' wide ditch when it only has a 15'' culvert in it; especially when the 15'' culvert is more than enough to handle the volume of water flow.

 

[LBrown59]

----->> 1* As for the small culvert in a deep ditch. I have some like that too. Most of mine are caused by land owners not allowing me to go upstream and redesign the ditch.
......>>> 2* As for a hole at the edge of the road. I avoid those at all costs. In one case I installed 120 feet of culvert so I could design a slope on each side gentle enough to mow. Your example sounds like they put in too short of culvert. Again, poor workmanship.
********

1*What caused this here is erosion of the bottom and cave in of the sides of the ditch several times during the 40 years I've lived here.
Each time the state would just dig out the bottom of the ditch without repairing the caved in sides and each time they would dig a little deeper down.
The result is the ditch is much wider and deeper than it was when I first moved here.
2*This hole is what's left of a run that no longer exist. The run could not be filled in clear to the end due to the state having a culvert running under the road 15 feet below the road surface. Filling in the last few feet of the run would have buried the inlet of the sates culvert under 13 feet of earth and blocked the water flow into it.
As a result we now have a section of the road ditch that is 15 feet deep 25 feet long and 20 feet wide
This is a rather bad situation for traffic as it's only about 3 feet from the edge of the blacktop to the edge of the hole.