A rain garden is a landscaped feature designed to capture, filter, and infiltrate rainwater where it falls. It is a shallow depression filled with native plants and permeable soil that mimics the natural processes of soil and vegetation.

When it rains, water runs off impermeable surfaces such as roofs, parking lots, and streets. Without vegetation to slow down or absorb this runoff, water quickly flows into storm drains, often carrying pollutants such as hydrocarbons, heavy metals, pesticides, and nutrients like phosphorus and nitrogen.

In a rain garden, runoff water is directed using gutters or natural slopes toward a filtration area. The water slowly infiltrates the ground, where it is filtered by layers of soil and plant roots. This process helps reduce the amount of contaminants reaching waterways while also helping to recharge groundwater supplies.

In addition to contributing to sustainable stormwater management, rain gardens help reduce flood risks during heavy rains, enhance biodiversity by creating habitats for insects and birds, and beautify urban areas.

Without rain gardens or vegetative cover, runoff becomes faster, more abundant, and more heavily polluted, contributing to water quality degradation and the eutrophication of water bodies. Rain gardens thus represent a natural, effective, and aesthetic solution to limit the environmental impacts of human activities.