What is the purpose of a riser in stormwater management?

• A. To remove floating debris from the surface.
• B. To control the water level within a basin or pond.
• C. To increase pollutant removal through filtration.
• D. To dissipate energy at the outlet.

Answer: (B)

A riser in a stormwater basin serves to set and hold the water surface at a specific elevation, effectively controlling the water level and storage volume. This structure connects to the outlet to determine how much water can be stored and when it can be released, ensuring a predictable detention time and a controlled discharge rate. It isn’t designed to remove floating debris (that’s handled by trash racks or skimmers), nor to act as a filter (filtration happens through sedimentation and other treatment processes), and it isn’t primarily for energy dissipation (that’s done by stilling basins, weirs, or energy-dissipating devices). So the main purpose is to regulate the water level within the basin or pond.