What is a landscape designed to collect and hold stormwater runoff called?

A landscape designed to collect and hold stormwater runoff is referred to as a rain garden. Rain gardens are specifically designed to capture and utilize stormwater from roofs, driveways, and other impervious surfaces, allowing the water to infiltrate into the ground and soak away naturally. They are typically planted with native vegetation that not only thrives in the wet conditions but also helps to filter pollutants from the stormwater, improving water quality before it enters the groundwater or local waterways.

In contrast, a retention basin is often used to hold water for extended periods, but it is typically larger and designed for flood control rather than for the aesthetic and ecological benefits of rain gardens. Wetlands, while they can also hold stormwater, are natural or constructed ecosystems that support a variety of wildlife and plants, and their primary function is different from that of a rain garden. Finally, a drainage field refers to a system that manages wastewater and is not designed specifically for stormwater runoff collection.

Thus, the designation of a rain garden highlights its purpose and design, making it the most fitting answer in this context.