▁the ▁ch ute . ▁Rec ir cul ating ▁v ort ices ▁are ▁developed ▁between ▁each ▁step ▁which ▁allow ▁the ▁water ▁to ▁flow ▁over ▁the ▁top ▁of ▁the ▁v ort ices ▁and ▁sk im ▁over ▁each ▁step . ▁ ▁Energy ▁D iss ip ation ▁ ▁Where : ▁ ▁H dam ▁= ▁dam ▁cr est ▁head ▁above ▁the ▁down stream ▁toe ▁( m ) ▁ ▁H 0 ▁= ▁free ▁surface ▁elev ation ▁above ▁the ▁sp ill way ▁cr est ▁( m ) ▁ ▁H max ▁= ▁maximum ▁head ▁available ▁( m ) ▁ ▁d c ▁= ▁critical ▁flow ▁depth ▁( m ) ▁ ▁H ▁= ▁head ▁loss ▁( m ) ▁ ▁f ▁= ▁fr iction ▁factor ▁ ▁a ▁= ▁channel ▁slope ▁[ rad ] ▁ ▁Cav itation ▁ ▁Cav itation ▁is ▁the ▁formation ▁of ▁a ▁void , ▁such ▁as ▁a ▁b ubble , ▁within ▁a ▁liquid . ▁A ▁fluid ▁passes ▁from ▁a ▁liquid ▁state ▁to ▁a ▁v apor ▁state ▁due ▁to ▁a ▁change ▁in ▁the ▁local ▁pressure ▁while ▁the ▁temperature ▁remains ▁constant . ▁In ▁the ▁case ▁of ▁a ▁dam ▁sp ill way , ▁this ▁can ▁be ▁caused ▁by ▁tur bul ence ▁or ▁v ort ices ▁in ▁flow ing ▁water . ▁ ▁Cav itation ▁occurs ▁within ▁the ▁body ▁of ▁flow ▁of ▁a ▁given ▁distributed ▁rough ness . ▁However , ▁the ▁exact ▁location ▁where ▁it ▁will ▁occur ▁cannot ▁be ▁predicted . ▁In ▁the ▁case ▁of ▁ch ute ▁sp ill ways , ▁cav itation ▁occurs ▁at ▁veloc ities ▁between ▁ 1 2 ▁and ▁ 1 5   m