If you're designing a swale system, how "bad" is it to punctuate the swale line with an area designed to allow for vehicular access to areas below the swale? I'm thinking of putting in swales between a road and an area I want logged. The logging equipment would probably destroy the swale. It seems like my only option is to plan for a compacted causeway across the swale for heavy equipment access. I imagine folks in Australia have to deal with this a lot... thoughts? Is this commonly done? How heavily would the "sides" of the access-way have to be reinforced against the swale?
Site background: our soil is very well drained micaceous loam. Average slope is between 10 and 15 degrees. Rainfall is heavy, especially in early spring and early summer, and erosion is a major problem if ground is left bare. Soil depth is highly variable, ranging from 18 inches to 60. Bedrock is biotite gneiss with thick layers of crushable saprolite.
Why can't you just build a culvert bridge? They have been around forever.
Partially dig in a large enough pipe to take 1.5 times your maximum water capacity and fill in over it so you can drive across.
I could go on and on about the variations to the structure, I'm a fan of gabion retaining walls. Whether you go level across or have a bulging bridge is your fancy.
Just look around any suburb, every stormdrain/ditch goes right into a road and out the other end through culverts.
The hemispherical shape doesn't crush easy at all, regardless of if it's plastic, metal or cement pipe.