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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Steering fines in shallow lakes
Steering fines in shallow lakes
Author : M.H.P.JANSEN(1), A.L. DE JONGSTE(1), M. KLINGE(1), S. SCHEP(1), P. STOOK(2), G. EGBRING(2)
ABSTRACT
Many shallow lakes suffer from accumulation of fine sediment. The sediment may have several origins, such as erosion
of banks or shallows, degradation of peat layers, internal organic production, external inflow etc. Its composition may
range from organic to inorganic. The accumulation may cause several problems, ranging from problems for human use
of the water (boating, swimming, drinking water) to ecological problems (increased turbidity, loss of vegetation cover and
associated biodiversity).
Removing the sediment by dredging is usually expensive because of the large quantities, the large surface area that
needs to be treated and the costs associated with transport, storage and/or disposal. Moreover, dredging usually does
not restore the water ecologically.
An interesting solution to reduce or solve the problems with fine sediment in a cost effective manner is to steer the
transport of fine sediment with relative small measures. Fine sediment could be caught by the creation of lee areas,
where silt can settle. Depending on water depth and transparency submerged and/or emerged vegetation may develop,
thus increasing further settlement conditions and local biodiversity recovery. Depending on the specific functioning of the
system and other measures to be taken, steering the fines may contribute significantly to the ecological recovery of the
entire lake. Also the human use of lakes (e.g. ship navigation) can increase significantly.
The principle of steering fines in shallow lakes is applied in the Wormer- and Jisperveld, The Netherlands. The Wormerand
Jisperveld consists of three shallow lakes connected to each other by small channels or ‘reeven’. Banks of both the
lakes and the channels are eroding, especially the banks with orientation in south western direction. Due to the erosion,
large parts of the lakes and channels are filled with organic silt. This limits the flows and gives problems to boats,
because parts are too shallow for navigation.
In order to get insight in the wave attack and present transport patterns of fines, a numerical hydrodynamic model was
set up. Special attention was paid to the orientation of the grid and the interaction between currents and waves. After
that, the model was used to examine the best way to create lee areas and to optimise the effectiveness of measures.
The most promising measures were implemented in Wormer- and Jisperveld last year. Since then the silt transports
decreased significantly. In some lee areas emerged vegetation developed, demonstrating the potential of this approach
to solve problems with fines and to contribute to ecological recovery of the lakes.
File Size : 3,376,513 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 20/08/2015
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