▁where ▁an ▁u pl and ▁region ▁and ▁a ▁coast al ▁plain ▁meet ▁and ▁is ▁typically ▁prominent ▁where ▁rivers ▁cross ▁it , ▁with ▁resulting ▁rap ids ▁or ▁water falls . ▁The ▁u pl ands ▁are ▁relatively ▁hard ▁cry st all ine ▁bas ement ▁rock , ▁and ▁the ▁coast al ▁plain ▁is ▁so fter ▁sed iment ary ▁rock . ▁A ▁fall ▁line ▁often ▁will ▁re ced e ▁up stream ▁as ▁the ▁river ▁cut s ▁out ▁the ▁u ph ill ▁dense ▁material , ▁ ▁forming ▁" c " - sh aped ▁water falls ▁and ▁expos ing ▁bed rock ▁sho als . ▁Because ▁of ▁these ▁features , ▁river bo ats ▁typically ▁cannot ▁travel ▁any ▁farther ▁in land ▁without ▁port aging , ▁unless ▁lo cks ▁are ▁built . ▁The ▁rapid ▁change ▁in ▁elev ation ▁of ▁the ▁water ▁and ▁resulting ▁energy ▁release ▁make ▁the ▁fall ▁line ▁a ▁good ▁location ▁for ▁water ▁mill s , ▁gr ist ▁mill s , ▁and ▁saw m ills . ▁Because ▁of ▁the ▁need ▁for ▁a ▁river ▁port ▁leading ▁to ▁the ▁ocean , ▁and ▁a ▁ready ▁supply ▁of ▁water ▁power , ▁settlement s ▁often ▁develop ▁where ▁rivers ▁cross ▁a ▁fall ▁line . ▁ ▁Geography ▁ ▁The ▁slope ▁of ▁fall ▁zones ▁on ▁rivers ▁played ▁a ▁role ▁in ▁settlement ▁patterns . ▁For ▁example , ▁the ▁fall ▁line ▁represents ▁the ▁in land ▁limit ▁of ▁navigation ▁on ▁many ▁rivers . ▁ ▁As ▁such , ▁many ▁fall ▁line ▁cities ▁grew ▁around ▁transfer ring ▁people ▁and ▁goods ▁between ▁land - based ▁and ▁water - based ▁transport ation ▁at ▁this ▁point .