Satellite-derived Inter-annual Variation in the channel of the Nun River within the Niger delta system

Abstract

Understanding fluvial hydraulics and geomorphology are very important factors in the study of any river process. It becomes a difficult task when faced with a river that has very limited data. The only known survey of the Niger Delta is that by the Netherlands Engineering Consultants (NEDECO) conducted between 1959 and 1963. The study reported herein aims to determine the extent of changes that have occurred over time in the river channels and to establish the present position of the river relative to the maps used in the construction of a hydrodynamic model of the Niger Delta. Selected locations along the river channel of the River Nun sub-system and the Niger river bifurcation were sampled. Changes in channel bankline in the sampled regions over the last 40 years have been established using LANDSAT images, supported by NEDECO survey data.

The rapid changes that were discovered suggest a very dynamic fluvial system, which is characterised predominantly by accumulation of weak and highly compressible alluvial sedimentary deposits. These changes suggest the Nun River moved towards the northeast in the upstream reaches, and to the south in the downstream reaches, between 1963 and 1998. However, between 1999 and 2002, the Nun River moved back to the approximate location determined in 1963 by NEDECO. Thus, the changes have been roughly reversed in the Nun River, but not completely in the downstream reach. Other sampled regions of the Niger delta have shown a less stable behaviour, including westward propagation of the sandbar\'s bar-head at the junction of the Nun and Forcados Rivers and southward movement of the channel of Oguobiri Creek.

KEY WORDS: Niger Delta, Bifurcation, LANDSAT, Sandbar, Bankline.

Global Journal of Geological Sciences Vol.3(1) 2005: 85-95