The geological setting of the Upper Mefou Catchment is similar to that of Yaoundé and the surrounding areas on the Southern Cameroon Plateau. The Yaoundé belt is a Meso‐ to Neo‐proterozoic unit, aging from 700 to 1000 million years (aka Panafricain), on the southern edge of the Central African Fault Belt. The belt consists of granulites and migmatitic gneisses.
The relief of the Upper Mefou Sub‐catchment can be divided into three major morphological units:
- The valley bottoms, which are covered by the rivers, floodplains, wetlands and the surrounding slopes. They are mainly located at altitude less than 725 m a.s.l. and are occupied by the Mefou Reservoir, and the densely settled areas of Nkolbission and the villages of Minkoamios, Ebot‐Mefou, and Nkolafeme.
- The zone of the middle altitude (peneplains: 725 to 850 m a.s.l.) are rolling hills. Most of the small villages are located here.
- The peaks from more than 850m to the highest point of the Catchment at 1221 m a.s.l. are inselbergs, made up of resistant rock residuals. Except from some rocky outcrops, they are predominantly covered by dense rainforest and are not under human use. The sources of the Mefou River are located here.