Changes in the Course of the River Komadugu Yobe during the 20th Century at the Border between Niger and Nigeria

Abstract: The river Komadugu Yobe in the Lake Chad basin is a seasonal river, about 370 km long and with an average highest flow of 34 m3/s during the time period of 1957 to 1976. The river is dynamic with plenty of meanders and oxbow lakes along its sides. Komadugu Yobe’s thalweg (the line defining the lowest points in a riverbed) is the natural border between Niger and Nigeria and may change position with the river. The objective of this study is to explore if and how the course of the Komadugu Yobe has changed during the 20th century and the impact this has on local inhabitants. Another objective is to look at similar examples in the world where the problem with a pending border exists and how this problem is dealt with. The study only concerns that part of the river constituting the border. Maps and images on different scales and resolutions from the 20th century were compared in a GIS-program to identify possible changes. Subsequently, field observations were conducted in villages along the river together with officials representing local Niger government to permit verification of the observed changes and as a mean to understand the impacts. The results show various changes along the river: a meander that has been cut off, change in the course and erosion. It is confirmed that the river has changed its course at numerous times during the 20th century and continues to do so. The most palpable influence of this change, as concerns local populations, is erosion of the riverbanks, which destroys and threatens houses and fields.