Hydraulic Resistance Characteristics of Riparian Reed Zone in River

Abstract

The riparian vegetation zone plays an important role in river ecosystems, flow resistance, water velocity distribution, and water level variation. In this paper, the impacts of riparian reed zones on river flow and water level were studied by comparing measurements in river reaches with or without riparian reed zones in the Chaodongweigang River of Taihu Lake Basin, China. The effects of the density, stem diameter, and rigidity of reeds on flow regime, water velocity, and water level were investigated. Subsequently, flow resistance on the river’s longitudinal water level caused by the riparian reed zone was studied. The results showed three water velocity zones in the river reach where there were riparian reeds, including the slack water zone, the transition zone of flow velocity, and the river’s main flow zone. The water velocities in the three zones were related to reed density, diameter, and rigidity. The water-surface slope in the river reach with a riparian reed zone was larger than that without a reed zone. It showed that the riparian reed zone influenced the river flood discharge to some degree and resulted in increased water level upstream. Additionally, the water level of the river cross section exhibited a concave shape that the water level was higher in the riparian reed zone than in the center of river midstream, section with a riparian reed zone exhibited a concave shape; the water level was higher in the riparian reed zone than in midstream, and the water level difference was influenced mainly by the reed density.