Development of ecosystem-based flood mitigation approach - investigations by experiments and numerical simulation

The purpose of this research was to understand how to minimise the destructive effects of floods by establishing a bio-shield of natural vegetation. Experiments were conducted in a water flume to determine the flow properties under different vegetation conditions whereas; volume of fluid (VOF) multiphase approach with a standard k-e turbulence model was developed for a simulation. The study involved comparative analysis of flow structures and loss of energy in a single patch of finite length, layered (single or double layer with gaps) and continuous (full width) vegetation models. The results showed that, for a single patch, the increase in vegetation density and aspect ratio increased the backwater rise in front of vegetation, reduced velocity and enhanced energy dissipation. Furthermore, in the case of horizontally layered vegetation models (single and double horizontal layers), the loss of energy was higher in double horizontally layered vegetation layouts. Gaps between vegetation patches of a single horizontally layered vegetation model possessed high flow velocity, which was countered by providing a second horizontal layer of vegetation with an alternate gap. The findings from this research are critical in designing optimum vegetation layouts for flood mitigation.