Flow characteristics in an alluvial channel covered partially with submerged vegetation

Abstract

The present study examines the flow characteristics in a stable alluvial channel partially covered with submerged Oryza sativa (rice) stems in a staggered pattern with downward seepage. Measurements were taken in transect across the flume at the vegetated region, interface or junction of vegetated and unvegetated region an unvegetated region to explore the difference in flow characteristics in these regions. The presence of vegetation reduces the velocity, Reynolds stress and turbulent intensities at the downstream vegetated region even with downward seepage which is an important finding for river restoration. An increase in the flow characteristics such as velocity, Reynolds stress and turbulent intensities are observed in the unvegetated region as the flow goes downstream which means that the reduction in the flow characteristics in the vegetated region is diverted towards the unvegetated region. Moment analysis shows that streamwise flux is occurring in the flow direction and vertical flux is occurring in downward direction and increases with increase in seepage percentage. Integral scales also exhibit that with downward seepage, the size of eddies increases. The maximum depth of erosion with downward seepage is more than for the case of no seepage and erosion increases as the flow goes downstream.