16. Gully Erosion Sites in Southeast Nigeria: Prospects for Geotourism

Gully erosion occurs in many parts of Nigeria under different geologic, climatic and soil conditions, with varying degrees of severity. However, the South East of Nigeria is the major gully erosion precinct of Nigeria. This chapter describes geomorphological processes leading to gully formation in the study area and highlights various gully erosion hotspots. Major processes that lead to gully formation in the southeast are knick point formation/slumping from surface runoff, swelling and shrinkage of soil, heaving and landslide, lateral bank failure and undercutting. Gullies are formed on the major highland and plateau areas whose precipitous escarpments are formed by sandstone bedrocks (Ajali sandstones and Nanka sands). Gullies on these formations are deep (about 50 m), long (over 1,200 m) and wide (about 30 m) and usually anastomosing, while gullies formed on the lower slopes and plains that are mainly underlain by shale units (Imo, Mamu, Nsukka and Bende-Ameki Formations) are single-channel and moderate in size. Nanka, Ekwulobia, Orlu, Okigwe, Isuikwuato and Bende areas are extensively dissected by these gullies.