Rain Garden underway

We are in a drought we have been thinking of any or all ways to capture and conserve  water for the garden. We intend to redirect water that flows down the driveway during a rain storm into the flower bed. In order to this and not wash out the flower bed  we will construct a french drain/rain garden 1 to 2 feet deep, 2 feet wide and about 30 feet long along the road and at the top of the slope. We will redirect the runoff with sand bags into the swale lined with tumbled stones that we dug up in another part of the garden. Most french drains are constructed  of stones with a perforated pipe at the bottom of the swale  to redirect water somewhere. Most rain gardens are held in place by plants to filter the water. Our design will be borrowing from these two ideas. Our swale will run perpendicular to the slope and water will perk slowly through the permeable subsurface down the slope to the lawn. We have begun the project with a U.C. Berkeley Landscape Architecture undergrad student, volunteers and our interns from Albany High School EDSET program.