Daphne van der Wal – physical geographer at NIOZ and professor at the University of Twente – observes deltas, coasts and estuaries from space and from the air. ‘That can be done via satellites but also with the help of drones. The use of these remote sensing techniques can teach us a lot about coastal defence, water quality and nature conservation.’
‘Satellites have the advantage that, in many cases, they allow us to look back over several decades. This is because we have a long history of satellite images which have continually observed a piece of the Earth’s surface in the same way. For example, from satellite images, we can see where coastal vegetation, such as saltmarshes and mangroves, has expanded and where plants have disappeared or where their growth was hampered. We analyse satellite images in relation to coastal protection for the Dutch coast, but also for the coast of Louisiana, for example. Together with modellers, we are examining how vegetation attenuate the waves and trap sediments and can reduce the chance of the land becoming flooded during heavy storms. That allows us to learn what the ingredients are for sufficiently strong coastal defences. Such information is becoming increasingly relevant in light of the changing climate and expected increase in extreme weather.
‘Satellite images are also well suited for studying the quality of the water and the seabed. For example, we examine the interaction between sediment and the algae and animals that live in the water and seabed. This knowledge is important with respect to, for example, the dredging of estuaries for shipping.’
‘We also use radar images; these can detect, for example, the roughness of tidal mudflats. This way, radar can even be used to map mussel and oyster reefs on tidal mudflats. Now we can also make use of techniques like drones; these provide very detailed spatial information.
With all these forms of remote sensing, we are finding out how our coastal systems work and how they adapt to changing conditions and interventions. We are also learning how coastal processes help us, and how we can protect our coasts.’
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I am a physical geographer, specialized in coastal processes (PhD 1999, University of Amsterdam; postdoctoral research fellow from 1 Oct 1999 up to 1 Jan 2002 at Royal Holloway, University of London). In Mar 2002, I joined NIOO/NIOZ in Yerseke, focusing on remote sensing of tidal (eco)systems. Since Oct 2017, I am also part-time full professor at University of Twente, Faculty of Geo-Information Science and Earth Observation (ITC).
Publications can be found at my ORCID and at UT Pure.
Theme
The central theme of my work is to assess interactions between organisms (such as saltmarshes, algae, shellfish) and their environment, shaping the estuarine, delta and coastal landscape, including both the bottom sediment and the water column. Topics also include the response of estuarine and delta systems to (climate) change and human impact, as well as risks (e.g., flooding) and services (e.g., nature-based flood risk reduction) of the coastal zone.
Current research topics
Methods & techniques
I use remote sensing techniques and geo-informatics and data science to investigate coastal and estuarine systems and processes:
See also ongoing projects at UT/ITC, Dept Water Resources, e.g. my participation in EU REWRITE (rewilding European shorelines and beyond) and NWO SaltiSolutions (solutions to address salinity intrusion in urbanized deltas).
Results from the NWO project Saltmarshes under stress
Laengner, M.L.; van der Wal, D. (2022). Satellite-derived trends in inundation frequency reveal the fate of saltmarshes. Frontiers in Marine Science 9, 942719. https://doi.org/10.3389/fmars.2022.942719
Laengner, M.L.; Siteur, K.; van der Wal, D. (2019). Trends in the seaward extent of saltmarshes across Europe from long-term satellite data. Remote Sensing 11(14), 1653. https://dx.doi.org/10.3390/rs11141653
Results from the EU FAST project
The EU FP7 project FAST (Foreshore Assessment using Space Technology), 2014-2018, has developed services to help design nature-based flood risk strategies in foreshores, based on earth observation data and big data analysis capabilities. Although the MI SAFE downstream service is not available anymore, some of the resources are available here: