Keeping draught depths and controlling sedimentation by making use of innovative geotextile
Type:
Presented during:
CEDA Dredging Days 2015 - Innovative Dredging Solutions for Ports, Rotterdam
Authors:
Lauwerijssen FM, Stook PJ and Egbring GAR - Tauw Group, the Netherlands; Jansen MHP - Witteveen+Bos,
Abstract: Due to wave action and water currents unprotected shorelines erode and natural habitats are lost. Sediment is kept in suspension, thereby inhibiting growth of higher order aquatic plants and natural water quality improvement. In a protected wetland area innovative and sustainable measures have been undertaken to reduce hydrodynamics, sediment resuspension and turbidity in order to keep draft depths, enhance biodiversity and improve water quality. Two types of light weight geotextile constructions were built to steer fines and to store sediment: the Sediment Settler and Sediment Storer. Due to the Sediment Settler fines transport decreased by 20-40 %. One year after installing the Sediment Settler a few decimeters thick sediment layer had already been formed at its lee side. Also about 15.000 cubic meters of slightly polluted sediment was dredged and transported to Sediment Stores in order to alter hydrodynamics and induce nature development. By doing so, maintenance costs were minimized and sediment had been beneficially re-used. By the end of the first growing season the sediment top layer was covered by a pioneer vegetation of reedmace. Even species that have disappeared 30 years ago returned. This pilot study has shown that it is possible to control sediment settling and transport and improving recreational and ecological quality of this wetland area. Nautical bottlenecks were reduced and in lee areas vegetation develops. So, synergies were realized between remediation, nature restoration and (at some locations) shore line protection. Dredged material can easily be kept and stored in submerged basins.
Key words: Geotextile construction, sediment storage, shoreline protection