Auxiliary Spillways

Learn more about the importance of spillway design criteria at DamFailures.org

“An auxiliary spillway is infrequently used and may be a secondary spillway (augmenting a service spillway discharge capacity). During operation there could be some degree of structural damage or erosion to the auxiliary spillway due to releases up to and including the maximum design discharge. Auxiliary spillways may be less robust, erosion-resistant structures consisting of some cast-in-place reinforced concrete, riprap channel protection and/or unarmored excavated channels”.^[1]

In the past, auxiliary spillways were commonly referred to as " emergency spillways". This practice should be discontinued. Media references to flow through “emergency spillways” often leads to a misconception by the public that an emergency condition exists at a dam when the dam is safely functioning as designed. ^[2]