Hi. I'm Pat. I live in downtown Ann Arbor within the Allen Creek floodplain. I have 2 rain garden spots I am considering. One would be fairly long and narrow, and would need to take in the front third of the house's roof runoff: It's got quite a slope, and this would be a fabulous way to get rid of a very scruffy lawn the has been infiltrated with an unmowable sedge. The other spot would take up part of an existing flower bed and a small patch of lawn--basically I would like it to go driveway to driveway. My neighbors to the north are already interested in this process. They have drainage issues. What you cannot really see in this picture is the enormous silver maple in the yard behind this one that shades a third each of their yard, my yard, and my neighbor's house to the north. One question that came to mind yesterday while listening to the discussion of distance from house, is how this would apply to dry wells. I had one put in several years ago, and I now suspect it may be contributing to the damp corner in the basement.

I love your analysis! And you have prioritized your options - which is great. I think you are on the right track. Your plans seem sound. :) I don't see any roadblocks. And the front yard location will be stunning! I can't wait to see your planting plan.

Hi Marieta. This looks like a great idea! The water already goes there, so you are one step ahead. Go for it! Next step, think about plants. This could be a beautiful flowering border!

Your only job when you build this rain garden is to make sure that the rain garden bottom is at least 4 inches *deeper* than the pipe. Use this calculation: The ~20' of pipe has to slope downward, so that the water makes it to the rain garden. So figure out how much that pipe needs to drop. Here is a quick calculator that calculates the *bare minimum* of drop your pipe needs to have. For safety, I would double it. https://www.builderscalculator.com/drain-pipe-slope-calculator/ For your 20 feet of length, I get 2.5 inches of pipe drop. Double that, and you get 5 inches. Plus the depth of the rain garden (4 inches) and you get your digging depth: 9 inches. If you want to live dangerously, you could dig a bit less - but No Shallower Than 6.5 inches! This is measured from where you think the bottom of the pipe will be once they build the patio. This might be pretty deep. At least 8 inches deep. So that gives you a total of 9+8=17 inches deeper than your ground level near the house. How to measure that where the rain garden is? Put up your stakes with a string between. String it where the pipe will start and finish - ground level near the house, and level it with a line level. Then measure down 17 inches from the string where you will be building your rain garden. It can be this deep, OR DEEPER. Deeper is fine. It just can't be any shallower than this. And since the ground slopes away from your house already, you won't have to dig the whole 17 inches. It will be less than that. All that sounds do-able - don't you think? :)