As the water level in the swamp goes up and down with the seasons dirt can wash away from the culverts. That can leave the pipe exposed
and the road rutted. When one has a pipe that's too short to get the road bed up to the level of the banks it's that much worse.
We'll go back and add dirt every few years until we get tired of it
One year soon we'll get around to putting in a pipe that's long enough to raise the road bed to where it should be and big
enough to handle the flow as the flood waters recede.