Hydraulic and morphological patterns in a riparian vegetated sandy compound straight channel

Abstract

Emergent vegetation or trees are important riverine features and essential in hydraulic engineering including flood management and river restoration. Clearing up trees along river banks has been pointed out as a contributing factor to the severity of flood damages including financial losses and even fatalities. Thus, the effect of riparian vegetation on river flow must be clearly understood. The hydraulics and morphological patterns in a riparian vegetated sandy compound straight channel were carried out in the Hydraulics Laboratory, School of Civil Engineering, Universiti Teknologi Malaysia. Two-line steel rods with tandem and staggered arrays to simulate as rigid emergent vegetation were placed along the riparian zone of an asymmetrical straight channel. The Manning's n, depth-averaged velocity, boundary shear stress and morphological changes during shallow and deep floods are discussed in this paper. The findings prevailed that the staggered array riparian vegetation generated 4.5% flow resistance higher than the tandem array. The vegetation also altered velocity distribution which contributed to the boundary shear stress patterns in a compound straight channel. The flow velocity profiles were also related to the morphological changes in the channel.