Deltas, under pressure from climate change and increasing human activities, are undergoing transitions in their abiotic and biotic systems. Especially when the pressures exceed certain thresholds substantial or even irreversible changes (i.e. regime shifts) can take place. The transitions of deltas are complex as human impacts operate on a wide range of spatial and temporal scales, while internal buffers and processes in the systems also set specific reaction time scales. Identifying how processes at different spatial scales, involving physical and biological mechanisms and their interaction, shape the resilience of estuarine systems will be adamant to understand and optimize the adaptive capacity of estuaries in an uncertain future.
The objectives of our project are to identify and determine the relevant thresholds, regimes and time scales, and to explore measures for coping with the transitions. The study is multi-disciplinary, covering hydrodynamics, sediment dynamics, geomorphology, biogeochemistry and ecology. Our approach focuses on the interactions of physical and biological processes at multiple spatial scales, linking rivers to estuaries and the adjacent coasts as a continuum. We will study changing fluxes of sediment, nutrients and pollutants between terrestrial, riverine, estuarine and coastal sources and their impact on estuarine delta morphology from mega-scale (sediment budget and longitudinal profile) and to macro-scale (channel-shoal structure), and meso-scale to study shifts in estuarine primary productivity and food web, transitions in tidal flat and salt marsh biogeomorphology, and environmental assessment and adaptation.
We will study transitions in the Yangtze Delta (China) and the Rhine-Meuse-Scheldt-Ems Deltas (Netherlands). These deltas are physically different and in different phases of transition with respect to engineering works (NL: since 1930’s; CN: since 1980’s), nutrient loading, pollutant loading and use of natural resources. However, they are facing the same management issues, i.e. guarantying safety against flooding, optimizing economic use (navigation, land reclamation, using fresh water and other materials) and protecting environmental value and biodiversity. The underlying scientific questions are the same. This forms the ideal base for our Sino-Dutch cooperative research.
In our approach, we will combine monitoring databases, field measurements, manipulative field and lab experiments (using unique new instruments) and diverse remote sensing applications, with advanced modelling tools. Joint field campaigns by Dutch and Chinese researchers together will be carried out in China as well as in The Netherlands. Models will be open source, multidisciplinary and involve different groups of researchers. Deliverables of the study are scientific publications, improved tools such as numerical models and decision support to the managers of the deltas.
In the Strategic Alliance phase of the PSA project, we aim to deepen and broaden our successful collaboration (started in the Project and Programme Phase of PSA). We will deepen our collaboration by progressing through the use of innovative techniques and innovative models. We will widen it by i) including larger-scale interactions between estuaries and their upstream rivers and adjacent coasts, and ii) defining integrated mitigation measures against anthropogenic impacts and climate change. We will continue our successful cooperation between the four participating institutes, by exchanging staff and students, organizing workshops, carrying out collective field campaigns and publishing joint papers. We are confident that our cooperation will become a mature scientific alliance during the Strategic Alliance Phase and beyond.
Bram van Prooijen 