Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE credits
The recently established Nairi reserve, twenty kilometres south of Siquirres, on the eastern slopes of the Talamancan Mountains, creates a buffer zone to the neighbouring Barbilla National Park. The reserve and its surroundings have been affected by frequent land slides, and ravines have developed. Furthermore, eastern Costa Rica was in april 1991 devastated by a huge earth quake which measured 7,4 on the Richter Scale.
In this study one of the ravines in the reserve is mapped, GIS-models of it are constructed, and grain size analysis of soil samples taken from the ravine, are performed. Furthermore, the ravine and its surroundings are examined and different map models are made.
The material in the ravine consists of silt and clay. After the big earthquake in 1991 the total amount of sediment, and sediment concentration in the river Barbilla has increased, this even at low flows.
As a combination of the humid climate in the region with frequent intensive precipitation, the uniform, rich deposits of fine-grained material, and the big earthquake, were large amounts of loose material over vast areas were released, the conclusion is that the ravine was probably formed by an earth flow, initiated by a land slide on a slope, close to saturation. The human impact in this case has probably been low.
2004. , p. 59