you say a drainage ditch...
so i assume. this is not a creak, or small river. that has constant flowing water. or perhaps a small trickle of water going through it. from drainage tile from surrounding fields. and for most part pretty dry throughout the year.
if you need to go through this area, alot throughout the year. i would say, a culvert and be done with it. that way you do not have to deal with muddy mess, or risk getting stuck within the area. and not needing to bring in rock in attempt to keep the area drive-able.
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the problem with creaks and small river like areas. and wide long flat area. is they can experience gully washers. that takes everything down stream. and trying to keep a good solid base of rock down. so you can drive through the area when needed as needed.
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examples to above.
i have a 3/4 to 1 acre lake. and on one end i have for most part 1 foot wide 1" stream feeding into it. (drain tiles from multi fields drain into this little drainage ditch that feeds the lake) over the years things have washed down to make it 10 to 13 feet deep area. and about 20 to 30 feet wide. for me it was easier to drop a 12 inch culvert down. and then bring in dirt to place over culvert. (a lot of dirt) but less hassle long run dealing with muddy washouts, and hills.
on another spot on the property there is a creak that is about 3 to 4 feet wide and about 4" deep pretty much year around. and then "gully washers" that can be 9 to 13 feet wide, and 5 to 6 feet deep of water. for this area, years ago wide / long area was cut into the creak. and a lot of rock was brought in. for a good solid base. now 30 to 40 years later. i am need to redo the entire thing again. much of the original rocks have sunk away. or silt has built up covering the old rock base or rocks have moved down stream making the area impassable. and when it was usable, even then it had to be during "dry times" of the year.
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what i am getting to in above is....
what is your general location? so folks can get rough idea of overall rain / temperatures of your area. (yes i realize your name is Missouri Pioneer, but folks move or working at another location)
can you get some actual pictures of location?
how much water actually flows through the area? width, depth for example. or other like details.