high debit wapama falls flowing over the footbridge and creating hazardous conditions for crossing; hetch hetchy reservoir area,

america area base bridge california conditions creating crossing dam danger dangerous debit drop falls fatal flowing foot footbridge granite hazard hazardous hetch hetchy high inundate landscape mist mountains national nature nevada overflowing park powerful reservoir risk risky rock safety scenery scenic sierra spills spray states steep strong trail united usa valley wall wapama water waterfall yosemite