Samenvatting

Ever since lake Volkerak got its status as a partially closed-off lake in the late ‘80s, excessive (cyanobacterial) algae blooms in the summer period have been a consistently occurring problem.
This research aims to investigate the location-specific effectiveness of wetlands and floodplains in nutrient removal. By developing these natural areas in the areas upstream of lake Volkerak, nutrients are partially removed, resulting in a decrease in frequency and intensity of algae blooms.
Wetlands and floodplains are known for their provision of various ecosystem services. This makes them an excellent choice for implementation, as they utilize natural processes and are capable of providing various benefits to plants and animals living in the area. Nutrients in these natural areas can be removed in various ways, including plant uptake and soil accretion. Factors such as plant species and abundance, oxygen availability and water retention time may affect the efficiency of nutrient removal.
Wetland and floodplain design types are analyzed and put into context of the specific research area. The resulting locations of interest are summarized in chapter 4 – Results. The selection of these locations is based on morphological and hydrological characteristics, elevation levels, proximity to the main river and presence of existing natural features. Analyses of nutrient concentrations, a nutrient balance and water levels provide more supporting theoretical context and are used for location selection.
The resulting thirteen locations and areas of interest in chapter 4 provide the basis for future similar research. Along the river Steenbergse Vliet, a total of six locations are assigned. In the river system Mark-Dintel, a total of six locations are assigned as well. Directly adjacent to lake Volkerak, one location is assigned in close proximity to the Hollands Diep.
The information and conclusions that are provided in this report can be used for the potential realization of the project in the near future. It is expected that the total surface area of the thirteen described locations is insufficient to reach the desired nutrient removal. Nevertheless, the proposed developments in these areas can contribute to habitat provision, various ecosystem services and (local) water quality improvements.
Future similar research should aim to focus on the expected effects of the proposed developments on biological and ecological aspects of the area, taking into account the area-specific characteristics.