The Impacts and Implications of Anthropogenic Forces on the Unstable Geologic Platform in Parts of Anambra and Imo States Southeastern, Nigeria

摘要

Anthropogenic activities have exacerbated the incidences of floods, soil and gully erosion and landslides in parts of southeastern states of Anambra and Imo, Nigeria. Intense urbanization, deforestation, agricultural, commercial/industrial activities has extensively-denudated and elluviated the total environment. The variations in climatic condition also have associated implications. The rainy season registers an average annual rainfall of 2000 mm. The Geology comprises an unstable platform of a regional escarpment/cuesta subtended by sandy, highly-fractured and faulted Nanka sands/Ameki Formation. The underlying unstable geology facilitates the development of gullies with depth ranging from 2 m to over 80 m. The calculated rate of soil removal from the gully prone areas is about 9.20 to 10.16 ton/ha/yr. The significant cuesta of the area with steep scarp slope and gentle dip slope forms both surface and groundwater divide that also facilitates gully and landslide developments. The underlying geologic sandy structure is quite porous and permeable with huge aquiferous horizons of high pore-water pressures and effective stress. The problems of laissez faire attitude and poor understanding of the destructive implications of the unstable regional geologic platform result in the failure of measures to prevent myriads of environmental destructions and economic wastes.