Large scale Nature-based Solutions deliver flood protection and nature restoration in the Scheldt Estuary
Type:
Presented during:
CEDA Dredging Days 2026
Authors:
F. De Keuleneer, L. Sittoni, T. Maris, P. Meire, S. Baeten, L. Van Nimmen and I van der Vijver
Abstract
The Scheldt Estuary has undergone centuries of anthropogenic modification, resulting in substantial ecological degradation and increased flood risk. In response, the Flemish Government implemented the updated Sigmaplan, which includes large-scale Nature-Based Solutions such as Flood Control Areas with Controlled Reduced Tide (FCA-CRT). These engineered systems restore tidal dynamics within embanked polders by using high-inlet and low-outlet sluices to generate a reduced but ecologically functional tidal regime. This study evaluates eight years of hydrodynamic, vegetation, and sedimentation monitoring within the FCA-CRT of the Kruibeke-Bazel-Rupelmonde polder, the largest CRT system in the Scheldt basin. Hydrodynamic observations demonstrate that the sluice configuration successfully reproduces spring-neap variability and creates a wide range of inundation frequencies, enabling the development of diverse intertidal habitats. Sustainable marsh development was assessed using a combined dataset of Marker Horizon (MH) and Surface Elevation Table (SET) measurements collected across seven monitoring campaigns. Annualized accretion rates were derived for 40 plots and related to geomorphological and hydrodynamic covariates including elevation, flooding frequency, distance to tidal channels, and suspended particulate matter. Regression analyses indicate that flooding frequency is the dominant predictor of spatial variability in accretion, whereas distance metrics exert weaker effects. Site-wide accretion averages approximately 6 mm yr??, with SET data showing that shallow subsurface processes contribute locally to variability but exert minimal influence on the system-scale mean. Overall, results show that the FCA-CRT at Kruibeke delivers effective flood storage while supporting the development and vertical resilience of tidal marshes, illustrating the potential of controlled tidal restoration as a nature-based solution for estuarine management.