Thomas J. Coulthard

The 2020 Ralph Alger Bagnold Medal is awarded to Thomas J. Coulthard for establishing landscape evolution modelling as a robust approach to geomorphological investigation, changing how geomorphology is studied and communicated, and promoting open research.

For the past 20 years Thomas Coulthard has been a world leader in the emerging science of erosion and landscape-evolution modelling and a visionary researcher at the forefront of the development and establishment of landscape-evolution modelling as a scientifically robust approach to geomorphological investigation. Whereas many workers in landscape-evolution modelling have focussed on the long timescales relevant to the creation of new landforms, often doing so in a highly idealised fashion, much of Coulthard’s work has focused on important shorter-term problems related to climate impacts and environmental perturbations.

Coulthard seeks not just to explain topography and landforms, but also to understand geomorphic processes as part of an integrated system that includes climate, hydrology, vegetation and human impacts. His innovative, simulation‐based approach to geomorphological research investigates aspects of landscape evolution that are impossible to disentangle with more traditional field-based approaches. Particularly, Coulthard conducts controlled simulation experiments to investigate process interactions and to assess relative influences of driving forces of landscape evolution. Examples include work on simulating catchment response to climate and land use change; simulating non‐linear dynamics of catchment sediment yield, leading to the important observation that autogenic perturbations of sediment yield can be of the same magnitude as tectonic‐ or climate‐driven perturbations; and, more recently, numerical simulation of geomorphic sediment connectivity in landscapes. In addition, Coulthard’s research has made ground‐breaking contributions to the understanding of geomorphological dispersion of inorganic contaminants.

One of Coulthard’s enduring contributions is his development of the CAESAR-Lisflood landscape evolution model, which has become extensively used around the world in academia, government and the private sector. Coulthard has also been an early supporter of open research. From its inception nearly 25 years ago, CAESAR has been open source and open access. Moreover, Coulthard has consistently shown a willingness to extend or adapt the code for collaborators’ research needs. This support for open research and collaboration positions Coulthard as an exemplary citizen of the broader geomorphic community.

Coulthard’s commitment to the geomorphology community is further exemplified by his tireless work for the British Society for Geomorphology (BSG) and the European Geosciences Union (EGU). For the BSG Coulthard has led a highly valued retreat for starting PhD students over the last 10 years. He is also the founder and managing editor of EGU’s open‐access journal Earth Surface Dynamics, which under Coulthard’s leadership has rapidly established itself as one of the world’s leading geomorphology journals.

In summary, Coulthard is a truly world‐class academic who has made significant and lasting contributions to geomorphology by conducting ground‐breaking research, by changing how geomorphology is studied and communicated, and by being an exemplary promotor of open research. Thomas Coulthard is a very deserving recipient of the Ralph Alger Bagnold Medal.