IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Hydro-environment : Sediment transport and underwater light climate affected by flexible aquatic vegetation
Sediment transport and underwater light climate affected by flexible aquatic vegetation
Author : JASPER T. DIJKSTRA (1) & MARIEKE M. VAN KATWIJK (2)
ABSTRACT
The ecosystem service of underwater vegetation to benefit coastal protection is increasingly recognized. However, the reconfiguration of these usually flexible plants makes modelling hydrodynamic modelling cumbersome. Flow and wave reduction are often modelled by assuming that vegetation increases bottom roughness, but this is not realistic as sediment dynamics would likely increase under that assumption. To avoid that, the actual flow reduction by the vegetation at the water-sediment interface needs to be taken into account. By combining a plant motion model (Dynveg) with a hydrodynamic and morphological model (Delft3D) and validating it in a real life situation, we succeeded in adequately simulating flow and sediment processes under influence of aquatic vegetation. By evaluating scenarios with vegetation types that differ in density and flexibility, the model showed that suspended sediment transport was less affected by vegetation than bed load transport. Nevertheless, in all vegetated scenarios, the sediment concentration was effectively reduced, which resulted in increased water clarity. Because light limitation is probably the limiting factor for seagrass occurrence in deeper waters, we thus showed that, at a landscape scale, the presence of vegetation can extend the lower limit of occurrence. The model also shows that seagrass is more effective in preventing erosion than in reducing sediment transport. The effects of vegetation on sediment transports are likely more pronounced in shallower areas where plants occupy a larger part of the water column, or in more turbid water with higher suspended sediment concentrations.
File Size : 816,050 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Hydro-environment
Date Published : 20/08/2015
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