Vegetation in drainage channels: interface with sediment accumulation

Abstract

The cover of grassy vegetation on drainage channel slopes is arranged with the aim to prevent the slopes from erosion and protect the channels from wash products. Due to natural succession of vegetation and often unsatisfactory maintenance of channels, other herbs and woody vegetation usually oust previous grassland species on the slopes; herbs and bushes start occupying channel bottoms. This results in a drop in flow velocity that increases possibility of suspended sediment settling. To highlight the links between vegetation growth and sediment accumulation in channels, the investigations were carried out in random 337 drainage channel stretches that all together covered more than 30 km. It has appeared that: 1) occurrence of bottom vegetation depends upon the soil cover and length of time for plants to occupy the bottom (the direct correlation), and the channel catchment area, longitudinal gradient and presence of woody vegetation on slope (the antithetical correlation); 2) bottom vegetation increases silting and the share of organic matter in sediment, while the action of slope woody vegetation to silting and organic matter amount in sediment is reducing if bottom is overgrown; when bottom is not overgrown, woody vegetation acts silting-reducing if its spread on slopes exceeds the space here. Certain consideration concerning vegetation management in drainage channels is presented.