Han is Professor Emeritus at Delft University of Technology, as the chair of Sediment Dynamics. He is an expert on morphodynamics and sediment transport, and Senior Specialist on cohesive sediment transport at Deltares. He is participating in and responsible for basic research and consultancy on sediment transport and morphological development in estuarine and coastal environments. He has executed many hydrodynamic, hydro-thermal and hydromorphological studies all over the world as project leader and as expert in multi-disciplinary project teams, using the various mathematical models developed by Deltares. For many years, a major part of his work is dedicated to basic research into the behaviour and properties of cohesive sediments and the application of the results to estuarine studies. A part of this research is carried out during his part-time affiliation as associate professor with Delft University of Technology.