This is what a Forest Ecosystem Bioretention Swale looks like if you are standing back from it. Notice it is not manicured. It is not maintained. The foliage is purely volunteer.

There is a bioretention swale down the entire left side of this road. The swale is about 6' from the road edge. About 2 or 3 times a year county comes around with a brush hog and mows that 6' wide strip. The road is on a fairly steep incline. At least 5% slope. There are no dams built into it.

This is what the lawn side of a swale looks like. People typically keep their lawns mowed right up the tree line. The trees are growing on the direct edge of the swale

This is a close up photo of one of the swales. The swale is 6' wide and about 1' deep. The size is very consistent throughout Michigan on the dirt roads. Most of our rural roads are dirt. Pavement only occurs in villages and in cities. County digs these swales very quickly and just leaves them. They are not seeded.

This is another close up view of the swale

This is just another view of the same swale system. The trees form a very thin row inside and on the edge of the swale. The swale starts off with full sun vegetation. It is quickly converted to a full shade habitat. The debris from the leaf fall of the trees and the die back of the vegetation keeps the swale fed with new sources of organic matter which act like a sponge in rainfall events

if the swale needs to be cut into a steep slope, they cut vertically into that slope and leave it that way. It isn't seeded and it doesn't erode. It is quickly taken over with vegetation