The Debris Flow of 1st August 2012 in Kakpenyi-Tinta (Akwaya Sub Division) Southwest Cameroon—I: Event Description, Causes and Impacts

摘要

Compared to large-scale infrequent disasters like volcanic eruptions, earthquakes, and gas explosions from volcanic (maar) lakes, most small-scale everyday disasters (e.g., landslides and floods) are not well reported and documented in Cameroon, despite the fact that cumulatively, they cause the most casualties and distress to the people affected. This paper documents a debris flow that occurred on the 1st of August 2012 in Kakpenyi, a quarter found in Tinta, one of the villages of Akwaya Sub Division in Manyu Division of the Southwest Region of Cameroon. The event started from the western slope (06 style="white-space:nowrap;"> style="font-family:Verdana, Helvetica, Arial;font-size:11.818181991577148px;line-height:17.27272605895996px;white-space:normal;background-color:#FFFFFF;">°14.350'N & 09 style="white-space:nowrap;"> style="font-family:Verdana, Helvetica, Arial;font-size:11.818181991577148px;line-height:17.27272605895996px;white-space:normal;background-color:#FFFFFF;">°31.475'E) of a hogback in the settlement, and mobilized ca 3.47 × 106 m3 of material over a ca 1 km distance. The material was made up of a chaotic mix of mud, rock fragments, boulders, twigs, tree logs, trunks, and roots. Its distal part dammed river Kakpenyi forming a 10 m deep lake which eventually safely emptied itself. No casualties were recorded but 20 people got injured and 21 people lost farmland. The debris flow was not caused by earthquake shaking. Instead, inappropriate land use acted as a remote cause to predispose the steep slope, while heavy rainfall triggered the flow. Verbal reports talk of a similar event 40 years ago in the area. This shows that Kakpenyi is vulnerable to this kind of hazard, requiring that major infrastructural development projects like roads and bridges in the area be preceded by detailed hazard and vulnerability assessments.