Giles Lesser promotes successfully
In the field of coastal morphodynamics, the study of the changes in channels, shoals and coastlines, prediction models used to be either too simple or difficult to run over large timescales.
Giles Lesser has tackled these problems by introducing fully three-dimensional modelling of morphology and by testing techniques to apply such models over longer time periods (up to many years), in his thesis ‘An approach to medium-term coastal morphological modelling’, which he successfully defended on June 4th.
Lesser implemented three-dimensional suspended transport in the well-known Delft3D package and coupled it with the computation of bottom changes in a very direct and effective way, leading to a much more robust overall system than previous approaches.
He started on the problem during his UNESCO-IHE masters study at Delft Hydraulics (now Deltares) and continued to develop and validate it during his subsequent work there and at the US Geological Survey.
On the US West Coast he studied several large tidal inlets and developed techniques to cope with the strong variability of the winds, waves, tides and water levels at various time-scales.
In a very systematic study he investigated the individual effects of each schematization, and found that these schematizations had very little effect on the quality of the outcome. They allow us then to apply a so-called ‘morphological acceleration factor’ that makes long-term simulations more efficient by orders of magnitude.
Because of this work a large number of researchers and engineers are now investigating morphodynamic changes on timescales and at a level of detail that was previously impossible.
However, as he says in one of his propositions, shortcomings in physical process knowledge and uncertainty inherent in ‘random’ future events are much greater obstacles to making coastal morphological predictions. Enough work left to do, it seems.
