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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Flood risk management and adaptation : Storm surge attenuation in a large intertidal marsh: impact of marsh geomorphology
Storm surge attenuation in a large intertidal marsh: impact of marsh geomorphology
Author : JEROEN STARK(1), YVES PLANCKE(2), STEFAAN IDES(3), PATRICK MEIRE(1) & STIJN TEMMERMAN(1)
ABSTRACT
The potential of coastal wetlands to reduce flood risks is becoming more recognized, while studies on the quantification
of storm surge attenuation in marshes are scarce. Here, in-situ water level observations in a tidal marsh as well as 2D
hydrodynamic modeling are used to study the influence of marsh geomorphology on tidal propagation and storm surge
attenuation for varying hydrodynamic boundary conditions in Saeftinghe, a 3000ha tidal marsh along the Western
Scheldt estuary (SW Netherlands). Water level measurements, conducted at different locations in and around a 4 km
long marsh channel during several spring-to-neap cycles and a severe storm surge, show that damping or amplification
of tides within the marsh area depends on the height of the tidal wave compared to the marsh platform elevation.
Undermarsh tides, with peak water levels below the platform elevation, are slightly amplified along the converging marsh
channels. Overmarsh tides with peak water levels above the marsh platform are mainly attenuated, with maximum
attenuation rates of up to 5cm/km along marsh channels for tides that inundate the platform by 0.5-1.0m. A
hydrodynamic model is set up with TELEMAC-2D to assess a wider range of peak water levels and include simulations
with variations in the marsh geomorphology. The effect of marsh vegetation is herein implemented by increased bed
roughness. Model results indicate that tides are only attenuated if the channel depth and width are small and the extent
of the marsh platform is large, while tides are slightly amplified if the channel depth and width are large and the influence
of the platform is less. The model results confirm the dependency of flood wave damping or amplification on the peak
water level relative to the marsh platform elevation for all scenarios. Finally, model simulations show that storm surge
attenuation can be limited by the marsh storage area, due to blockage or reflection against levees or other man-made
structures that surround the marsh area.
File Size : 1,359,542 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Flood risk management and adaptation
Date Published : 18/08/2015
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