Investigation of Gully Erosion in Owerri, Southeastern Nigeria Using Landsat (ETM) and Aeromagnetic Data

Abstract

Gully erosion is the most obvious form of soil erosion in southeastern Nigeria mainly because of the remarkable impressions the gullies make which are also visible manifestation of the physical loss of land that will have been used for Agriculture and infrastructural development. Gully erosion is a well-defined water worn channel. Gully erosion, the most impressive and striking erosion type, has been recognized as one of the major global environmental problems. Observations have shown clearly that gully erosion is more prevalent in sedimentary terrain than in the basement complex of Nigeria. This erosion activity at various scales has resulted in the loss of lives and properties almost on a yearly basis. This work is about gully erosion study of Owerri using remote sensing and aeromagnetic data. This study is aimed at giving a detailed interpretation of the remote sensing and aeromagnetic data of the study area. This work identifies and studies gully erosion in the study area, Owerri and its environs in Imo State, South Eastern Nigeria which is located between latitude 5.18° – 5.39° N and longitude 6.51°- 7.08° E. Aeromagnetic data (maps) where acquired from Nigerian geological survey Abuja the images was obtained using land sat ETM sensor with band combination 2,3 and 4 with resolution of 30m. The processing of the land sat images and the aeromagnetic data where done using ILWIS 8.0 and 10.0, ILWIS Academia, ARC GIS, ERDAS, Q GIS. These software’s have the capacities of carrying various data enhancement techniques such as linear enhancement, statistical analysis, principal component analysis. The interpretation of aeromagnetic survey data is aimed at mapping the subsurface and the subsurface regional structures such as faults, folds, contacts, bodies and vegetation.