The Impacts of Micro-Topographic Changes on Mangroves in the Lower Reaches of the Benin River, Niger Delta

摘要

Oil exploration and related activities in coastal wetland areas created the need for dredging to construct navigable access. This study was carried out in the lower reaches of the Benin River to measure topographic profiles across five oil installations access canals. Soil chemical parameters and vegetation density and diversity were also studied at these sites. The results of the micro-topographic measurements of the abandoned spoils show that the elevations of the five spoil deposition sites ranged from 1.63-2.54 m above the lower low water spring tide datum (>LLWS), with a mean of 2.31 m>LLWS, whereas, within the control intact mangrove swamp, the elevation was 1.36 m>LLWS. Therefore, the abandoned spoil dumps were 95 cm higher than the control area. These micro-topographic changes coincided with soil chemical properties and vegetation changes leading to the emergence of upland and/or freshwater species in mangrove areas. The study concludes by affirming that the resultant spoils that are often abandoned as canal banks as a result of oil exploration related dredging activities, have caused micro-topographic changes in the Niger Delta leading to changes in soil chemical properties causing a shift in the vegetation pattern of the area.