The Arthur Thomas Ippen Award was established by the IAHR Council in 1977 to memorialise Professor Ippen, IAHR President (1959-1963), IAHR honorary member (1963-1974), and for many decades an inspirational leader in fluids research, hydraulic engineering and international co-operation and understanding.

The Award is made biennially by IAHR to one of its members who has demonstrated conspicuously outstanding ability, originality, and accomplishment in basic hydraulic research and/or applied hydraulic engineering, and who holds great promise for continuation of a high level of productivity in this profession.

In 2025 the 24th Arthur Thomas Ippen Award was bestowed upon Prof. Dr. Bernhard Vowinckel during the opening ceremony of the 41st IAHR World Congress (IAHR2025) on Monday 23 June 2025, at the Singapore EXPO.

The following Ippen lecture will be given in during the IAHR General Members Assembly during the 41st IAHR World Congress (IAHR2025) in Singapore EXPO on Thursday 26 June 2025.

Small is beautiful: What we can learn from grain-scale processes about sediment transport

Sediment transport is ubiquitous in the environment and plays a major role in shaping the landscapes we live in today. In the face of global climate change, it will become increasingly important to understand these processes in order to make reliable predictions about their intensity. It is already clear that the increasing frequency of extreme weather events can trigger dynamics with sometimes catastrophic consequences. Due to the multiscale nature of the processes involved, ranging from the grain scale to entire watersheds, reliable predictions of sediment transport remain elusive. This talk will therefore provide an overview of the current state of knowledge on the use of hybrid small-scale experiments and numerical simulations of sediment transport under controlled boundary conditions to inform a bottom-up approach that can parameterise larger scale models.