The Kuiseb Canyon is carved by the Kuiseb River, and it forms the southern edge of Namib Desert Park.
The Kuiseb River in Namibia flows from the Khomas highlands west of Windhoek to Walvis Bay. It is bordered on one side by the tallest sand dunes in the world, and on the other by barren rock. The red sand dunes south of the river reach heights over 150 meters. The prevailing winds blow the dunes northward, but their movement is blocked by the river. In the process, so much sand and silt is deposited in the Kuiseb that it only reaches the sea while it is in flood, i.e. very occasionally.
See below satellite image of the Kuiseb river (source NASA).