The 21st International Workshop on Physical Processes in Natural Waters (PPNW) has been held in Solothurn, Switzerland, from 20 to 24 August 2018. The workshop is co-hosted by University of Geneva and Eawag.

The PPNW workshops focus on the physics of inland and coastal water bodies and their interactions with the physical and biogeochemical processes that drive water quality and ecosystem functioning. The 21st workshop in Switzerland pays special attention to the physics and functioning of freshwaters in light of global environmental change (eutrophication and climate change). Studies presented in the PPNW Workshop focus on topics addressing such changes in the context of physical-biogeochemical interactions, biogeochemical cycles, greenhouse gases and general limnology. PPNW is an open workshop, actively seeking to expand contact and collaboration with neighboring fields such as physical oceanography, atmospheric sciences, and engineering.

Within this context, Dr. Soler, Dr. Colomer and Dr. Serra, in collaboration with Dr. Folkard from the Lancaster University (United Kingdom), contribute to the PPNW 2018 with an oral presentation entitled “Effect of full and patched vegetated canopies on turbidity currents: hydrodynamics and sediment”. In this study, the authors measured hydrodynamics and sediment deposition rates when turbidity currents flowed into both full vegetated canopies and vegetated patches in a lock-exchange flume experiment, using simulated vegetation and three real plant species, and varying the turbidity current’s initial sediment concentration in the range 1.0-6.0 gL^-1. The natural sediment used had an essentially bimodal size distribution, with coarse (6.2-104 μm) and fine (2.2-6.2 μm) fractions. Results show that the size segregation of deposited sediment within the full and patched vegetation canopies is posited to have important consequences for substrate evolution, which in turn may affect vegetation growth, and to have an impact on an essential ecosystem process, biogeochemical nutrient recycling. Thus, findings of this study point to a non-linear feedback mechanism between the spatial heterogeneity of vegetation canopies and that of the substrate they help to engineer.

In addition, Dr. Serra, Dr. Colomer and Dr. Soler, in collaboration with Dr. Oldham from the University of Western Australia, contribute with a poster entitled “Local hydrodynamics in fragmented seagrass canopies”.

Both studies were developed within the framework of the “Water Quality and Particles Transport” research line of the Environmental Physics group, and of the of the Fragmentum project.