DISTRIBUTION CHARACTERISTICS OF SEDIMENT AND NUTRIENTS AROUND GROUPED RIVER GROYNES

Abstract

 Sediment and nutrients are essential components linking the physical environment and the eco-system in a river. In order to understand the environment function of river groynes, the distribution characteristics of riverbed sediment and phosphorus, one of the essential nutrients, around a group of groynes have been investigated. The study is conducted by field surveys and numerical simulations for groynes along a curved channel of the Kokubu River in Kochi Prefecture, Japan. According to the research results, phosphorus concentrations in the water are associated with the in situ flow conditions and those in the riverbed are related to the local bed morphology. In local scales, the scour holes around groyne toes are covered by coarse sediment with small σ_g, where the phosphorus concentrations are high in the water and low in the riverbed. While in the depositional areas of the groyne bays and groyne wake, fine sediment materials with large σ_g are dominant and the phosphorus concentrations are low in the water and high in the riverbed.