▁feet ▁per ▁second , ▁but ▁period ically ▁it ▁is ▁in und ated ▁by ▁tor r ential ▁flo ods ▁from ▁its ▁ste ep , ▁er os ion - pr one ▁mountain ▁waters hed . ▁The ▁reputation ▁of ▁Ar roy o ▁Sec o ▁flo ods ▁led ▁the ▁Spanish ▁to ▁site ▁the ▁original ▁P ue blo ▁de ▁Los ▁Áng eles ▁away ▁from ▁the ▁confl u ence ▁of ▁the ▁Ar roy o ▁Sec o ▁and ▁the ▁Los ▁Angeles ▁River . ▁Histor ically , ▁these ▁flo ods ▁would ▁race ▁down ▁the ▁stream ▁bed ▁and ▁overflow ▁through ▁Pas ad ena , ▁South ▁Pas ad ena , ▁Al h amb ra ▁and ▁Los ▁Angeles ▁communities ▁all ▁the ▁way ▁to ▁the ▁Los ▁Angeles ▁River . ▁As ▁Los ▁Angeles ▁developed ▁into ▁a ▁city ▁and ▁grew ▁out wards , ▁the ▁damage ▁from ▁these ▁flo ods ▁was ▁particularly ▁severe ▁in ▁ 1 9 1 4 ▁and ▁ 1 9 1 6 . ▁ ▁Dev il ' s ▁Gate ▁Dam ▁In ▁ 1 9 2 0 ▁flo od ▁engine ers ▁from ▁the ▁Los ▁Angeles ▁County ▁Flo od ▁Control ▁District ▁built ▁Dev il ' s ▁Gate ▁Dam ▁in ▁the ▁Ar roy o ▁Sec o , ▁the ▁first ▁flo od ▁control ▁dam ▁in ▁Los ▁Angeles ▁County . ▁It ▁is ▁managed ▁by ▁the ▁Los ▁Angeles ▁County ▁Department ▁of ▁Public ▁Works . ▁N amed ▁for ▁a ▁rock ▁out cro pping ▁which ▁res emb les ▁the ▁face ▁of ▁a ▁devil , ▁Dev il ' s ▁Gate ▁g orge , ▁located ▁in ▁northern ▁Pas ad ena ▁between ▁La ▁C añ ada