Landslide impacts and management in Nanka area, Southeast Nigeria

Geoenvironmental Disasters

Ogbonnaya Igwe¹  Chuku Okoro Una² 

[1] 0000 0001 2108 8257, grid.10757.34, Department of Geology, University of Nigeria, Nsukka, Nigeria;Department of Applied Geology, Wesley University, Ondo, Nigeria;

关键词: Impacts;    Limit equilibrium;    Mitigation;    Biotechnical;   

DOI  :  10.1186/s40677-019-0122-z

来源: publisher

【 摘 要 】

The devastating impacts and mitigation measures for landslides in Nanka, Southeast Nigeria were studied. A procedure encompassing field mapping, laboratory analysis and limit equilibrium simulations were employed in the study. A total of 120 landslides in this area were documented during the field study. They were mainly shallow landslides with depth range of 0.2 m – 1.8 m and slope angle range of 36o - 65o. This study revealed that landslides in this area occur mainly during the rainy season, and are triggered by water infiltration in slopes with high gradient, where poorly consolidated sands overlies less permeable silty clay units in the Nanka Formation. The increase in pore water pressure due to soil saturation leads to reduction of the shear strength and loss of apparent cohesion. Geotechnical laboratory analysis showed that the thin silty clay soils found in the area have very high plasticity, while the sands are non-plastic. The limit equilibrium simulations revealed that as the slope angle increases, the potential slip mass volume increases. Our study in Nanka revealed that landslides have negatively affected the topography/morphology, settlement areas, agricultural lands and vegetation/land cover of the area and many areas are also threatened by this phenomenon. Standard mechanical drainage system and biotechnical slope protection have been suggested as mitigation measures. Finally, we suggested that landslide hazard information should be incorporated into long-term plans for Nanka and other areas prone to landslides, the public should be aware of the hazards and preventive measures.

【 授权许可】

CC BY