While it is admirable to reconstruct an entire riparian floodplain, small steps, can really make a difference too.      Rain Gardens can range from a small depression in a rear yard to a comprehensive system of engineered soils, overflow drains and native plants as proposed at Benedictine University.   The primary purpose of a rain garden is to store the initial inch of rain, often referred to as "the first flush", to help the water infiltrate into the ground and limit the amount of runoff pollutants continuing downstream. Small rain gardens can make a big difference.

The optimal time to construct and plant rain gardens is between May-June.  Most rain gardens consist of natural depressions that contain approximately 1-3 feet of amended soil with approximately 50% sand and 50% landscape compost soils.  A 2-4 inch layer of mulch is usually applied atop the soils.  Rain gardens should be designed to hold no more than 6 inches of standing water.An overflow weir or underdrain is essential to maintain proper water levels.  Once excavation is complete and the planting bed is installed, you can utilize a variety of species in a rain garden.  The key to plant selection is to choose species that can tolerate both wet and dry conditions. 

While native plantings are typically best suited to be used in rain gardens, you may also consider using a couple of cultivars as well.  Traditional landscape plants can help transition your new rain garden to the more manicured portions of your site.