Effect of submerged tropical macrophytes on flow resistance in open channel: An experimental study
Abstract
Recently, aquatic macrophytes is widely applied to water quality improvement and ecological river restoration projects. On the other hand, the macrophytes can considerably alter flow resistance, thereby, conveyable capacity of a channel or river. In this study, the laboratory experiment in a glass-walled flume had been conducted to quantitatively investigate the effect of different morphology of submerged macrophytes on the flow resistance. The laboratory flume is rectangular in cross section and has dimensions of 15m length, 0.6m width and 0.6m height. A ply-wood floor was fabricated and fixed on the bed of flume in order to keep the macrophytes stable in the flume. Three common submerged species in tropical region was selected for this study, including Cabomba caroliana, the very flexible specie, Eichinodorus grandiflorus, the less flexible specie, and Nymphaea rubra, the floating leaved specie. The macrophyte was arranged in a patch located in the middle of flume with 6m length, 0.6m width, a specific height and different densities. The flume was run with different discharges such as 10 L/s, 20 L/s, 30 L/s and 40 L/s, and two level of tailgate weir corresponding to approximately 20cm and 30 cm of water depth in stagnant situation. Using Acoustic Doppler Velocimeter and needle ruler, mean velocity profile and water level in the cross-sections along the flume were measured. Each measurement campaign was consistent with specific combination of discharge, tailgate weir level, and density of the macrophyte species. Based on the measured results of changing pattern of flow field and flow resistance, which is expressed by the Manning’s n coefficient, compatible with each kind of macrophyte morphology were analyzed and discussed. Furthermore, quantitative values of Manning’s coefficient (n) depending on hydraulic parameters (e.g. mean velocity or Reynolds number) and measurable parameters of macrophyte morphology (e.g. density and submerged degree, Y/H), were proposed. These outputs provide useful information for calibration hydraulic and hydrological models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.H41B0897P
- Keywords:
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- 1630 GLOBAL CHANGE / Impacts of global change;
- 1805 HYDROLOGY / Computational hydrology;
- 1813 HYDROLOGY / Eco-hydrology;
- 1851 HYDROLOGY / Plant ecology