Design drawing of stepped rain garden

Quick answer：

A stepped rain garden is a landscape feature that utilizes the natural grading of the land to capture, filter, and infiltrate stormwater runoff. The design typically includes a series of stepped terraces, each with plants that are adapted to the wet conditions. These gardens are effective in reducing stormwater runoff, filtering pollutants, and replenishing groundwater. They are particularly useful in urban areas where traditional stormwater management systems are inadequate.