Which feature handles overflow in an extended detention basin?

Which feature handles overflow in an extended detention basin?

• A. Inflow
• B. Sediment forebay
• C. Riser
• D. Emergency spillway

Answer: (D)

Overflow control in an extended detention basin is provided by an emergency spillway. The main outlet or riser handles normal outflow and detention, but when a storm brings inflow greater than that outlet can pass, water rises to the level of the emergency spillway. It then carries the excess water away in a controlled path to prevent overtopping of the basin and protect downstream areas. The sediment forebay traps sediment at the inlet, reducing sediment load but not handling overflow. Inflow is simply the water entering the system. The emergency spillway is the feature specifically designed to handle overflow during extreme events.

Overflow control in an extended detention basin is provided by an emergency spillway. The main outlet or riser handles normal outflow and detention, but when a storm brings inflow greater than that outlet can pass, water rises to the level of the emergency spillway. It then carries the excess water away in a controlled path to prevent overtopping of the basin and protect downstream areas. The sediment forebay traps sediment at the inlet, reducing sediment load but not handling overflow. Inflow is simply the water entering the system. The emergency spillway is the feature specifically designed to handle overflow during extreme events.