Rain gardens are an aesthetic feature of your residential landscape that also has a hydrologic function. Hydrologic means related to water. A properly designed and constructed rain garden for a residential landscape (no underground drainage system) is designed like a bathtub to hold water and let it slowly seep into the soil beneath the garden. This water is available for plant growth, and this water is removed from runoff that leaves your yard and does not contribute to downstream flooding or pollution. How well does your rain garden serve its hydrologic function?