A remote sensing-based evaluation of channel morphological characteristics of part of lower river Niger, Nigeria

Abstract

River bank erosion, accretion and lateral channel migration are important geomorphological processes, which attract a great deal of attention of river engineering scientists in many parts of the world. The present study assesses the morphological characteristics of parts of the lower section of River Niger, where field data are scarce and difficult to access for security and cost implications. Multi-date (1990, 2002 and 2017) Landsat imageries were used for the study, the imageries were corrected for geometric and radiometric errors, classified and analysed for changes in major land cover classes within the river channel, to assess river planform, riverbank pattern, channel width, bankline migration and centreline using ArcGIS software. The results revealed a decrease in water body and riparian vegetation by 27.64% and 9.77%, respectively, between 1990 and 2017. Sediment yield, however, increased by 75.61%. In addition, the river channel exhibited significant spatial changes within the study period; centreline at left flange shifted eastwards by about 1347.3 m at the upper section but westward at the lower section by 123.1 m. The bankline shifted prominently eastwards at right flange and westwards at the right flange. The study concluded that the studied channel had actually undergone some critical morphological changes greatly affected by erosion and accretion processes that are easily captured with remote sensed imageries.