Long-term effects of maintenance dredging on turbidity
van Maren, B.; van Kessel, T. (2016). Long-term effects of maintenance dredging on turbidity. Terra et Aqua 145: 5-14
In: Terra et Aqua: International Journal on Public Works, Ports and Waterways Developments. International Association of Dredging Companies (IADC): The Hague. ISSN 0376-6411, meer
Maintenance dredging is required in many estuaries worldwide to provide access to ports and inland waterways. Sediment is dredged from ports and access channels and disposed of by placing it back at another location in the estuaries. This results in a common belief that maintenance dredging practices lead to enhanced turbidity. Usually numerical methods are utilised to estimate the short-term effects and transport of disposed sediment but they are not designed to estimate the long-term effects of dredging. Quantifying the return flow of sediment from the disposal site to the port is a long-term process and therefore cannot be fully assessed using traditional methods. As such, the quantitative information available to optimise disposal locations for minimum ecological impacts and / or economic impacts is incomplete.
A recently developed dredging module within the open-source modelling platform, Delft3D, is able to capture the two fundamental processes necessary to model the long-term impacts of dredging on turbidity. These two processes are:
• sediment buffering in the seabed and; • integral modelling of ports and associated dredging requirements.
This model has been applied to three case studies where large amounts of dredging take place: the Ems estuary, the Scheldt estuary, and the Port of Rotterdam. Through these case studies the effects of dredging and disposal locations on long-term turbidity patterns and the return flow of sediment dredged from various ports can be quantified.
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