Circular use of harbor dredged sediment: sediment layer thickness optimisation for sustainable clay production
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
C. Mc Leod, M. Barciela-Rial, W. van der Star and M. van Puijenbroek
Abstract
The ripening of dredged sediment for different layer thicknesses on a dike was investigated. The focus of the field experiment was on the effect of thickness of the sediment layer and the initial vegetation length. Two scenarios were tested: 1) 3 cm layer sediment on 4 cm long vegetation and 2) 6 cm layer sediment on 20 cm long vegetation. The freshly dredged marine sediment from a harbour was diluted with fresh water to a workable density before it was applied to the dike test sections. The sediment was placed on the field experiment dike test sections to the required initial sediment layer thickness on top of the initial vegetation length. The evolution of the water content, organic content, ions dissolved in the water-sediment mixture and sediment layer thickness was measured. By comparing the results, it is seen that for scenario (1), the sediment layer thickness reduces by 70% within 6 days and maintains a constant thickness. For scenario (2), the sediment layer thickness reduces by 60% within 14 days before it reaches a constant thickness. The results of the sediment layer thickness reaching a constant thickness coincides with the water content evolution. The organic matter content results in the sediment layers showed a slight increase in thickness over time as the sediment oxidized on the dike. The results also show that most ions, which were measured, increased as time advanced. The initial mowed vegetation on the dike, for both scenarios, recovered rapidly and was able to grow through the sediment layers, with some species of vegetation benefiting from the increased amount of ions within the sediment layer. Overall, the results of this study represent a step forward towards the reuse of dredged cohesive sediments from harbors for dike reinforcement projects and therefore contribute to circular economy and flood protection policy programs within The Netherlands and worldwide.
Keywords: Sediment layer thickness, vegetation growth, water content, organic matter content