the hope river rises at the hope pass in the southern alps, which is the main divide for the south island. the river runs northeast through lake sumner forest park then south until it turns east along a large valley formed by the hope fault, a significant tectonic fault line. it is joined by a major tributary, the boyle river which flows south from the lewis pass some above its confluence with the waiau. the waiau enters from a side valley and continues eastward along the hope fault's valley before turning south through a gorge near hanmer springs.