"Below you is the valley of the Umzimkulu"

The Umzimkulu is the second largest river in KwaZulu Natal.  It rises in the Drakensberg and flows southeast, entering the Indian Ocean at Port Shepstone. 

The Umzimkulu valley, through which the river runs, remains predominantly rural (until it reaches the coast).  Parts of the valley look little different now than they did in the 1940s, when the novel was set.