Human impact upon sediment in rivers: Some examples from Hong Kong

Abstract

Examples of human impact upon sediment in water courses from Hong Kong are outlined. In the Kam Tin basin under baseflow conditions, two undisturbed upland streams exhibit low concentrations of suspended sediment as typified by median values of 4.8 and 1.6 mg l-1, while in contrast the river at Kam Tin has a median sediment concentration of 36.3 mg l-1. At Kam Tin values of suspended sediment concentration in excess of 20 mg l-1 account for a much higher proportion of samples than in the upland basins. The higher suspended sediment concentrations downstream at Kam Tin can be explained by the disposal of domestic, agricultural and industrial waste in the river. Evidence is also presented for the occurrence of higher suspended sediment levels in the Lam Tsuen River, which has been impacted by construction activity, in comparison to an undisturbed upland basin. In the future more attention might need to be given to the transport of plastic, polystyrene and other debris.