Winterbeek

The Winterbeek, a tributary of the Demer, meanders over a course of 32km from Beringen to Scherpenheuvel-Zichem. The Winterbeek changes names along the way, from Kleine Beek to Winterbeek, Zwart Water and, finally, Hulpe, before flowing into the Demer. NARMENA will focus on the area of Kloosterbeemden and Demerbroeken. 

Due to alternating dry and wet conditions and the transition from nutrient-poor to nutrient-rich environments, the Winterbeek valley is home to a wide variety of biotopes, each with their typical fauna and flora. The valley is therefore of exceptional importance to nature conservation and biodiversity in Flanders. Large parts of the valley have been designated as a nature reserve and are protected at European level under the Habitats Directive. It is therefore not surprising that this authentic streamscape attracts many hikers and nature enthusiasts. Agricultural and residential areas are limited in the valley. Local farmers have largely adapted their farming activities to the wet characteristics of the area. 

In addition to its importance as a natural area, the valley also acts as a flooding area. The storage capacity of the natural floodplains in this valley has a regulating effect on high discharges. The conservation of these zones is essential to prevent increased risk of flooding further downstream. 

The natural structure of the course of the Winterbeek is very valuable. There are few human interventions. For example, the stream has practically no artificial bank protection and still follows a natural course with many meanders. 

Research from the past years has shown that the Winterbeek is heavily polluted along a 17 km section, mainly by heavy metals and chlorides. The contamination is largely the result of earlier wastewater discharges from industries and households. These substances are carried along by the current and have accumulated in the sediments of the stream. The floodplain area and the banks are also contaminated by flooding and by the placing of cleared sludge on the banks. 

Today, the discharge of pollutants has stopped. However, historical contamination present in the sediment threatens, if not already present, the flood areas. 

LIFE NARMENA focuses specifically on techniques to remediate the heavy metals, particularly cadmium and arsenic. 

Since this subarea is of natural value, impactful remediation techniques, such as excavating soil and sediment are to be avoided. Nature-based remediation is planned here, in the context of LIFE NARMENA. However, it is important that the upstream sections of the river are tackled first, before measures can be taken in this area. In this sense, the planning of the pilot project depends on the timing of the remediation works in the upstream trajectory of the Winterbeek. To prevent extra influx of contamination, sludge traps are constructed at the start of the remediation works in the upstream sections to be tackled. 

Within the sphere of influence of the Winterbeek, in the Kloosterbeemden nature reserve, a constructed wetland is planned that will dampen the stream. Measures are defined to raise the groundwater to the level of the Grote Leigracht, almost permanently inundating the area. This will lead to reduction processes in the subsoil, as a result of which sulphides will be formed, that bind to the metals. This greatly reduces mobility and bioavailability, leading to immobilisation of the contamination and reduced uptake by organisms. Effectiveness and potential side effects will be closely monitored in the early years of the construction of the wetland. 

This type of wetland is a local natural phenomenon in the region, a starting point for many typical habitats to develop. It will therefore promote nature conservation and biodiversity. 

 

Planning

Hydrological modelling of different measures to raise the waterlevel in Kloosterbeemden has been carried out. Conventional remediation works in the upstream sections are finalized. The soil remediation project for this section of the Winterbeek has been submitted in 2021 and the permit has been granted in 2022. The works have started in September 2022, and lasted for one year. 

NARMENA is joining forces with the Sigmaplan to create the wetland. The Sigmaplan will help to make the Demer more resilient to flooding. The Demer is the southern border of the Kloosterbeemden. Various interventions on the Demer will reduce flooding downstream and our work will humidify the Kloosterbeemden. A win-win, therefore. Currently, certain measures taken by Sigmaplan, like connecting old meanders to the Demer, are being finalized.  

Monitoring the stabilisation of the contamination has started in 2023 and will continue until 2026. The first results are promising.