The Impact of Sand Mining on Riparian Areas of Eyaa, Onne, Nigeria

Abstract

Excessive sand mining in the Eyaa River, Onne, Rivers State, Nigeria has led to severe cases of land degradation manifesting as river bank erosion of riparian areas in Eyaa, Onne. An estimated land area of 142,000m² (equivalent to about 497,000m³) has been lost in the past five years (2010-2015) which has resulted in widening of the stream channel to more than double its original width prior to the commencement of sand mining in 2006. Instream sand mining leads to depletion of sand on the stream bed ultimately deepening the stream channel. Results of Particle Size Distribution tests of soils within 2.5-3.5m horizon revealed 6.8% fine sand, 61% medium sand and 31.9% coarse sand. Crumb tests results classify the soils as highly dispersive soils. This explains the undercutting and the eventual collapse of the river banks observed in the study area which poses serious threats to farmlands and built up areas within the riparian areas of the Eyaa River. The results of the study revealed that instream sand mining leads to the destruction of riparian habitat occasioned by changes in channel morphology and hydraulics, lowering groundwater level thereby affecting groundwater system in Eyaa community. A rapid collapse of the river banks initiates the development of gully heads and the current rate of land loss observed around the banks of the Eyaa River will potentially extend into the Eyaa community within 5 years if not checked. Moreso, collapsed stream banks and dredged spoils increases the turbidity of the river with severe consequences for aquatic species.

Keywords: Riparian, Dispersive, Crumb Tests, Channel Morphology, Hydraulics, Gully.