Grand Coulee, e.g. (5)
(Other definitions for dam that I've seen before include "A mad kind of mum" , "Mad as an animal mum" , "Female parent; obstruction" , "Reservoir barrier" , "Horse's mother" .)
(Other definitions for gorge that I've seen before include "chine" , "Eat greedily" , "Wolf" , "Eat too much" , "Eat gluttonously" .)