Cogmans Kloof (or Kogmanskloof) is a gorge through the Langeberg between Ashton and Montagu on the R62 and is named after the Cogmans, a Khoi chiefdom that existed in the area around the beginning of the 18th century.
The poort is almost entirely incised within intensely folded sandstone of the Table Mountain group and follows the course of the Kigna River, which flows southwest of Montagu. The formations in Kogmanskloof were deposited, folded, and faulted over 500 million years ago. At the Ashton (southern) end of Kogmanskloof, the Malmesbury group underlies these younger folded sandstones that dominate the scenery of the kloof.
A plaque fixed to the rocks just past the Activity Centre shows the height of the water in the kloof during these floods and acts as a reminder to all of the immensely powerful force of nature.
Just down the way from Avalon Springs lies Mazawattee, the hardest rock sports climb in South Africa! Only a handful of climbers have succeeded in getting to the top. Take a short walk down the kloof, and you may be lucky enough to watch in awe as climbers attempt to conquer this wave-like monster. The most striking feature of Cogmanskloof is how it cuts through the mountain range. Exactly which processes acted to form these features are unknown, but several mechanisms probably worked together to produce them.
The rivers may well have existed before the uplift of the mountain range, and their erosional power was able to keep pace with the rise of the land. The geomorphology of the kloof today is, in a sense, incredibly unique because it is undergoing continuous modification. Although in any single lifetime, little or no change may be apparent, over a long period of, say, millions of years, many aspects of the kloof morphology would have changed.
In January 1981, heavy rains in the southern Karoo caused the Keisie and Kigna rivers to flood and meet at their confluence in Montagu before rushing through Cogmanskloof to Ashton and the Breede River, with considerable loss of life and damage to property.