VEGETATED OPEN CHANNEL FLOW FOR URBAN STORMWATER MANAGEMENT: A REVIEW

The presence of vegetation in urban stormwater waterways such as swales plays an important role from ecological point of view as it can be used to improve water quality and reduce soil erosion by altering the flow magnitude. To understand the hydrodynamics of vegetation, numerous types of synthetic materials were used to simulate vegetation roughness in the past. Through this, numerous model equations were developed to predict the discharge, but the models were found to overestimate the discharge when applied to a natural vegetated channel or constructed one such as swales. This paper reviews some researches performed on vegetated open channels, which comprises the effects of vegetation characteristics on flow, modeling of vegetative roughness and derivation of vegetal drag coefficient due to submerged and emergent vegetation. Studies based on laboratory, field works and numerical modeling, have been reviewed based on previous approaches by different researchers. The paper concludes with recommendations for future work in order to improve the existing models for predicting vegetated roughness through the use of natural vegetation in combination of both the interactions of submerged, emergent and floating types of vegetation which is less investigated by researchers. For this reason, it remains questionable to precisely determine the optimum value of vegetative roughness for the purpose of vegetated channel design.