Will my rain garden kill my trees

[Clevland Spartan]

Hello,

I'm considering planting a rain garden to help reduce the standing water in my yard after heavy rains. My concern is that I will have to cut through a lot of tree roots from the big maple tree in my yard. I have attached three pictures one of which is a scaled sketch showing the layout of the tree and rain garden. There is also a picture of the tree with a bucket and carboy marking the corners of the rain garden closest to the tree and a picture of the standing water at its worst.

I would like to excavate approximately 24" for the rain garden. My question is what are the chances that this will kill the tree? Also if anyone has any better ideas for the rain garden or another solution for drainage I am open to that as well.

Appreciate any help

[rainbowgardener]

I'm no expert, but I would think it would be an improvement for the tree compared to all the standing water pictured.