The purpose of an emergency spillway is to provide:

• A. An overflow path during extreme events.
• B. Prolonged storage of runoff.
• C. Aeration of surface water.
• D. Filtration of dissolved nutrients.

Answer: (A)

An emergency spillway is there to provide an overflow path during extreme events, protecting the dam from overtopping. It acts as a back-up outlet that only engages when inflow and reservoir levels exceed the capacity of the regular spillway, or when the dam crest is at risk of being overtopped. By channeling excess water safely away, it helps prevent erosion and structural damage to the dam and downstream areas. This feature is not intended for storage, aeration, or filtration of water; its sole role is to relieve extreme water pressure and keep the reservoir and dam safe during floods.