It sounds like your soils will infiltrate the water quickly if they are dry and sandy! You'll want to choose plants that do well in drier conditions. Will the rain garden go where your patio furniture are? Looks like a good spot!

The whole slope is the rain garden. Dry stream bed has landscaping cloth underneath it and you notice the top of the stream bed has a small depression to retain some of the water the overflow goes down the stream. The Michigan stone walkway channels the water that doesn't go into the stream bed into the the lower elevation when it can pool around the red rock stone pool. The roots for the bush take up most of that water as will the ferns and other plans that are in that area once they get established. So that the lowest point is a collection area for all of the water that doesn't soak into the soil. Even in the worst storm we had so far this year there hasn't been any serious pooling of the water I think due to the amount of tree and push roots already present through out the area. The water source is the back half of the roof about 450 square feet. The front half does not have any gutters it falls off of the eaves onto rain dispersers.

OooOOo! An opportunity to use a sledgehammer! Or a jackhammer! Fun times! I think your idea is a good one. It appears that the slope down to the street is a bit steep - it could just be the photo, hard to tell. If so, keep in mind that you will be in berm-building territory, or a small rock wall, or something else. Could be very decorative! Love that you are solving a problem with this rain garden. :)

Hi Stephanie. Great! That seems ok. You are right on the cusp of loam/clay. So think about that when you pick plants - select those that like it a bit wetter than typical. But in general, this should work great. You are not on the "extreme edge" of the percolation rate, so all should be well.