Secondary Circulation in Partially Vegetated Channels

The fact that many cities developed near rivers show their importance to humans. Rivers and their adjacent low-lying areas provide abundance an diversity of wildlife and plants, and ample benefits to society including freshwater supply, water purification, flood regulation, recreation, among others. These benefits highly depend on the vegetation present inside and next to rivers which help regulating water quality, and promoting the retention of nutrients, heavy metals and sediments, and so play a major role in the functioning of aquatic ecosystems and water management. However, vegetation can also lead to rising water levels during heavy rainfalls causing a river to overflow onto adjacent lands and putting people, wildlife, and infrastructure at risk. Nowadays, we have flood early warning systems that alert people living close to rivers to leave the area before flooding occurs. These systems rely on mathematical and numerical models that assess the extent, depth, and velocity of flooding which should include the effects of vegetation growing inside and next to the river. Thus, an improved understanding of water movement and circulation between submerged vegetation and the open water may translate into conscious practical applications in river management that protects biodiversity and habitat but that also do not compromise lives. To achieve this, I am studying the circulation of water experimentally with a submerged patch of vegetation of different densities and widths, and at different submergence ratios (i.e. water depth to vegetation height ratio) to evaluate the impact of vegetation on water flow (in terms of how the water moves, their direction of circulation and its strength) and improve one of the existing simplified models use in flood early warning systems.