▁flo od ▁control , ▁prevent ▁er os ion ▁at ▁the ▁ends ▁of ▁terra ces , ▁out lets , ▁and ▁water ways , ▁reduce ▁run off ▁over ▁d rain age ▁d itch ▁banks ▁and ▁are ▁simple ▁to ▁construct . ▁ ▁However , ▁they ▁can ▁only ▁be ▁constructed ▁at ▁sites ▁with ▁natural ▁d rain age ▁and ▁moder ate ▁temperature ▁variation ▁and ▁have ▁a ▁shorter ▁life ▁expect ancy ▁than ▁other ▁sp ill ways . ▁ ▁Ste pped ▁sp ill ways ▁▁ ▁Ste pped ▁sp ill ways ▁are ▁used ▁to ▁diss ip ate ▁energy ▁along ▁the ▁ch ute ▁of ▁the ▁channel . ▁The ▁steps ▁of ▁the ▁sp ill way ▁greatly ▁reduce ▁the ▁kin etic ▁energy ▁of ▁the ▁flow ▁and ▁therefore ▁reduce ▁flow ▁velocity . ▁Rol ler - comp act ed ▁concrete ▁( R CC ) ▁stepped ▁sp ill ways ▁have ▁become ▁increasing ly ▁popular ▁because ▁of ▁their ▁use ▁in ▁re h abil it ating ▁aged ▁flo od ▁control ▁d ams . ▁ ▁Design ▁gu idel ines ▁for ▁these ▁sp ill ways ▁are ▁limited . ▁However , ▁research ▁attempts ▁to ▁assist ▁engine ers . ▁The ▁two ▁main ▁design ▁components ▁are ▁the ▁in ception ▁point ▁( where ▁flow ▁bul king ▁first ▁occurs — in cre ased ▁flow ▁depth ) ▁and ▁the ▁energy ▁diss ip ation ▁that ▁occurs . ▁ ▁Ste pped ▁sp ill ways ▁are ▁useful ▁for ▁flo od ▁control , ▁increasing ▁dissol ved ▁o xygen ▁( DO ) ▁levels ▁down stream ▁of ▁a ▁dam , ▁aid ▁waste water ▁treatment ▁plants ▁for ▁air - water ▁transfer ▁of ▁g ases