Scientific progress in sediment and water quality assessment: Implementation of practical case studies

The management of sediment, soil and water in the Netherlands dates back to the first settlements in the lower Northern and Western parts of the Netherlands. Around 500 B.C. farmers constructed ‘terps’ (artificial dwelling mounds) to protect against floodwater. The Romans (50 B.C. – 250 A.C.) reshaped natural waterways, to improve transport by ship. This also meant that river embankments were constructed and waterways and harbours had to be dredged. With the construction of river dikes in the period 700 – 1200 A.C. the sediment challenge began. The peatlands behind the dikes dried out, creating land below the average sea level. Dikes and dike maintenance therefore became crucial and since 1255 A.C. the first official governmental bodies, public utility boards (waterschappen) were created. These public utility boards together with the Dutch government, provinces and cities are still responsible for sediment and water quantity and quality. With this timeframe in mind, the scope of this thesis, examining developments in sediment and water quality management in the Netherlands over the past 25 years (1993 – 2018) is relatively short. A critical focus during these past 25 years was the heritage of industrial pollution of waterways and sediments from the early twentieth century. During the past 25 years changes took place in the way risks of contaminants in sediment and water were evaluated, partly due to scientific progress on the ecotoxicological impact of contaminants. As important as the scientific progress were the policy and legislation changes. These changes are driven by a broader spectrum of societal needs, like safety against flooding, scarcity of public funds and the need to change to a more circular economy using sediment as a resource. The goal of this thesis is to help water managers to understand the mechanisms
that change the ecotoxicological risks in their water and sediment systems, providing tools that go beyond the legislation requirements to assess these risks.