Over fall break, a group of student volunteers stuck around Oberlin to work with OSWAMP (Oberlin Storm Water Management Project) building rain gardens at several locations including the Oberlin High School, The Boys and Girls Club, and the J-House Garden!
Rain gardens are great for mitigating the amount of rainwater that runs into Plum Creek during storms. All of the storm drains on campus direct water right into the creek, which causes the creek to flood frequently, gradually eroding its banks away. Because the soil in Oberlin is generally very clayey, water washes off the grounds surface faster than it can percolate down to the water table. A healthy rain garden will hold water for up to 40 hours, allowing it to percolate into the soil more slowly and thus preventing spikes in the river’s discharge whenever it rains.
To build a rain garden, we remove a foot and a half of the clayey soil near a storm drain (usually in a lima bean shape, in a natural depression in the ground). Then we fill it back up with lighter, sandier soil that drains well. Finally, we spread a layer of gravel on top, and fill the area with a variety of of native, water-loving plants. The whole thing ends up looking like a zen garden in a golf course, at first. But next year, many of the plants will bloom with brilliant purple flowers and grow up to three or four feet tall.