Ton Hoitink appointed professor of Environmental Fluid Mechanics

In deltas, rivers branch out into inland channels that are influenced by marine influences. Extremely high discharges can compromise the safety of residents and strong currents can accelerate erosion. Extremely low tides can cause ships to run aground and can lead to salinity intrusion, which can have consequences for the freshwater supply. 'My research and teaching efforts focus on flow processes and river bed changes caused by river discharge, tides, wind and density differences between salt water and freshwater,' explains Hoitink. 'I combine knowledge from hydrology, oceanography and geology. A better understanding of delta flow processes is needed in order to develop environmentally friendly interventions that can help us counteract the effects of climate change, which leads to more extreme river discharges and rising sea levels.'

An intrinsic element of Ton's approach is the development of new monitoring methods based on acoustic, optical and radar measurements from ships, from fixed positions in or near rivers and from space. 'The synergy between alternative measurement methods and advanced data processing methods, such as the ones developed here in Wageningen, improves our understanding of the processes that contribute to bank erosion, salinity intrusion and shipping hindrances. There are very few measurements that provide insight into the flow processes during extremely high river discharge, despite this being determinative of erosion and sedimentation. There are also few measurements during low discharge, which can increase salinity intrusion in river deltas. Climate change calls for more intensive monitoring of delta areas with a higher spatial coverage that offers greater insights into crucial situations during extreme river conditions.'

Ton Hoitink is head of the Kraijenhoff van de Leur Laboratory for Water and Sediment Dynamics (behind Gaia). He and his colleagues conduct scale experiments in the lab to investigate the river bed dynamics resulting from the interaction between water and sediment. Ongoing research is part of a pilot study focussed on longitudinal dams recently constructed in the Waal river over a length of ten kilometres, to replace the river groynes. 'We received funding from the Netherlands Organisation for Scientific Research (NWO), the Directorate-General for Public Works and Water Management (Rijkswaterstaat) and Deltares to study flow processes in openings between the longitudinal dams, where water and sand are exchanged between the navigation channel and the side channel in between the dam and the river bank,' explains Hoitink. 'If the pilot project passes the evaluation, it may dramatically change the Dutch river landscape.'

Ton Hoitink studied civil engineering at the University of Twente and graduated from Deltares (formerly WL|Delft Hydraulics) in Delft. He then carried out his PhD research at the Institute for Marine and Atmospheric Research at Utrecht University as a member of the Physical Geography department. In addition to projects in the Netherlands, Hoitink conducts research on the Pearl and Yangtze deltas in China and the Berau, Mahakam and Kapuas deltas in Indonesia. These projects are funded by the NWO and the KNAW (Royal Netherlands Academy of Arts and Sciences).