Rain garden drainage

Asked July 29, 2019, 6:11 PM EDT

Hi there, We just moved into a new house in Ann Arbor. The laws here require all new construction to have rain gardens. As such we have two rain gardens: one in the front and one in the back. The back yard rain garden is very healthy - plant life is doing well and there's adequate drainage. The one in the front is not doing as well. Water sits on top of the entire surface area of the garden for about 36-48 hours after a rain. Moreover, the plants aren't growing. We have a 1 year warranty on the house and I would like to get the front rain garden fixed it is warranted. I'm curious about your opinion on this matter. Thanks, Kristin

Washtenaw County Michigan sustainable gardening and landscaping rain gardens

1 Response

A few things come to mind. This size garden may not be big enough to handle the water from the area that is draining into it. When rain gardens are designed there is a set formula for this. The size of the roof area that is directed into this along with any surface area that is draining into this site. It should be about 1/5 the size of the roof area that is draining into it and at least three inches deep. The other problem is if the site is such heavy clay below and surrounding it that it does percolate down into the subsoil quickly enough. A great resource in Ann Arbor is the Washtenaw County Water Resource Commissioner's Office where they have experts on Rain Gardens. I would contact them to see if they can determine how to best manage this situation. Contact Susan Bryan at bryans@washtenaw.org