What is the primary function of a rain garden?

The primary function of a rain garden is to remove nutrients and heavy metals naturally from stormwater runoff. Rain gardens are specially designed landscapes that capture rainfall from impervious surfaces such as roofs and driveways. The design typically includes a variety of plants, soil, and a distinct planting area that helps to filter out pollutants.

In this context, when rainwater flows into a rain garden, it passes through layers of soil and plant roots, which can absorb and break down harmful substances like excess nutrients (nitrogen and phosphorus) and heavy metals. This natural filtration process improves the quality of the water before it eventually re-enters the groundwater or nearby waterways.

While aesthetic appeal is an additional benefit of rain gardens, their primary role focuses on improving stormwater management and environmental health. Similarly, providing recreational areas or collecting stormwater for drinking is outside the primary scope of a rain garden's function. Rain gardens are not designed for drinking water collection as this poses health risks due to potential contaminants in the runoff. Thus, option B accurately reflects the essential purpose of rain gardens in managing stormwater and enhancing water quality.