Research Publications
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Publication Embargo The deflectors influence on flow complexity, bed morphology, sediment transport and water quality of urban lotic waters - A laboratory study(wiley, 2022-11-25) Sooriyaarachchi, D. T. A; Gomes, P. I. AIn this laboratory study different combinations of bed (sand, pebble gravel [gravel], and a mix of sand and gravel) and flow (typical and overtopping) were experimented with to investigate the impact of porous deflectors in flow diversity, water quality, and fish performance in prismatic open channels. Deflectors changed the gradually varied flow to a rapidly varied flow, as a sudden change in the water depth was observed at the deflectors, and this change was large for smooth beds. With the presence of gravel, the scouring near the downstream deflector was almost twice that of the sand bed, and with the scouring at its own upstream deflector, irrespective of whether the flow was typical or overtopping. This behavior was a result of sand mobilization due to shear stress and sand mobilization aided gravel transport. The mixed bed showed less gravel movement compared to the gravel-only bed. The percentage of sediment washed out was minor for all bed scenarios, indicating that sediment transport was local. Relative to the sand bed without deflectors (representing a typical urban canal), deflectors resulted in reduced and improved water quality (in terms of sediment load) for sand, and mixed bed, respectively. The fishes found refuge and were comfortable in the pool areas created by deflectors unlike in channels without deflectors where they showed exhaustionPublication Embargo Impact of increased instream heterogeneity by deflectors on the removal of hydrogen sulfide of regulated urban waterways—A laboratory study(Wiley Online Library, 2021-03) Gomes, P. I. A; Samararatne, S.; Wai, O. W. H; Perera, M. D. DLaboratory experiments were conducted to test the hypothesis that increase in physical heterogeneity by deflectors would improve the water quality of urban regulated (straight and prismatic) waterways. Deflectors changed the near-uniform flow to a rapidly var-ied flow, as such the depth, velocity, and Froude number (Fr) variations were four, 10, and 14 times more than the without deflector scenario, respectively. Removal of hydro-gen sulfide (H2S), the main focus of the study, was significantly high when deflectors were placed in the laboratory urban waterway. Introduction of a sediment bed further improved H2S removal; however, in this case turbidity and color were significantly high too. These observations endorse the fact that attenuation induced by deflectors and assimilation promoted by the sediment bed aids the H2S removal. These facts were fur-ther strengthened by the significant strong negative correlations H2S made with DO and pH for all experiments. Further studies are recommended for different deflector orientations and modified sediment beds (e.g., mixture of sediment and gravel), identi-fication of localized water quality hot spots to capture spatial variation of water quality, and impact of increased heterogeneity on flood safety