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 observe, 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.’Read more +
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
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 to investigate coastal and estuarine systems and processes:
- Output remote Sensing work package of a NWO NWA North Sea project on offshore wind parks. See article: Brandao et al (2023)
- Small contribution to NWO NWA small project, 2023, see here
- STW Perspective AllRisk – Implementing new flood safety norms. Project Foreshore Ecosystems Management. My role: co-applicant of project B (Dynamics in hydraulic loads). PhD candidate at NIOZ/RUG: Beatriz Marin Diaz (joint supervision NIOZ/RUG: Tjeerd Bouma, Han Olff, Laura Govers, Daphne van der Wal). See Beatriz' PhD thesis, and movie. See also the programme overview and programme outcome.
- NWO/NSO Ruimteonderzoek, “Saltmarshes under stress: thresholds for saltmarsh dynamics from global satellite data” (MARSH). See NWO project output.
- Satellite remote sensing of microphytobenthos in the Wadden Sea: analysis of 18 years of MODIS data , for Deltares, 2021.
- EU FP7 SPACE - FAST "Foreshore Assessment using Space Technology". Consortium Deltares, University of Cambridge, NIOZ Royal Netherlands Institute for Sea Research, University of Cadiz, GeoEcoMar. My role: work package leader WP3: Remote sensing. PhD candidate at NIOZ on this project: Bas Oteman, started 2014 . See Bas' PhD thesis. See also the overall project outcome.
- NWO/NSO Ruimteonderzoek: “Benthic diatoms as indicator for ecosystem structuring in shallow tidal waters. PhD candidate at NIOZ on this project Tisja Daggers, started 2013. See Tisja's PhD thesis.
- NWO/NSO Ruimteonderzoek: "Consequences of global change for ecosystem engineering of shellfish". PhD-candidate at NIOZ on this project Sil Nieuwhof, started 2012. See Sil's PhD thesis.
- Benthic invertebrates (macrofauna) of the shallow subtidal areas (van der Wal et al., 2017) and intertidal areas (van der Wal et al., 2017) of the Westerschelde estuary, for Rijkswaterstaat.
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. The MI SAFE downstream service is currently not online anymore, but the data can be found here and the metadata can be found here.
Read more on EU FAST in the associated article on this Copernicus downstream service for coastal needs.
See the results of the EU FAST project in the project synthesis report "Earth Observation and the Coastal Zone, from global images to local information".
Take a tour around the Danube Delta in Romania, one of the field sites in the EU FAST project!
See our instructional videos on field techniques, for example on the use of sedimentation sensors, as used to assess lateral saltmarsh cliff erosion in Van der Wal et al. (2023), and vertical sedimentation/ erosion in Willemsen et al. (2018), Hu et al. (2018), Hu et al. (2017) and Hu et al. (2015).