THEME 1: climate change including morphological evolution on long time scale (decades) for the Belgian coast as a whole | CREST project

THEME 1: climate change including morphological evolution on long time scale (decades) for the Belgian coast as a whole

  1. In concertation with Complex Project Coastal Vision, climate change scenarios for Belgium were agreed on.
  2. Although according to projected changes in the climate extreme waves conditions and storm surges are not expected to change much, sea level rise will increase the impact at the Belgian coast unless the level of coastal protection can grow at equal pace.
  3. A sea level rise of 2.4 mm per year for the last decades has been confirmed.  A temperature increase in the order of 0.1 degree Celsius per decade in Belgian waters has been observed. 
  4. Sea level rise will cause higher high tides and lower low tides.
  5. During the last four centuries, the Flemish coast straightened under the combined influence of human activity and natural evolution, advancing in the southwest area, retreating in the central area and both advancing and retreating in the northeast area.
  6. In the past 30 years, the natural sediment supply in the active zone of the Belgian coast was of the same order of magnitude (0.5 million cubic meter per year) as the artificial supply by means of nourishments. The natural supply is the result of cross-shore transport from the offshore towards the coastline. Detailed understanding in the driving mechanisms is still lacking.
  7. In the past 30 years, the natural sea defences at the western and eastern parts of the Belgian coast have heightened more (10 to 30 mm per year) than sea level rise (2 to 3 mm per year), while the central part naturally loses sand (loss of 2 to 8 mm per year). The western and eastern parts thus show a certain natural resilience to sea level rise contributing to the soft coastal defence. Climate change induced coastline retreat can be partly compensated by natural feeding.
  8. One-off events, like a storm, show little or no impact in the decadal beach volume morphological time series. Although not seen over the last decades, this does not exclude that extreme events could have a devastating impact.
  9. The increased replenishment efforts of the past years have realised permanently wider beaches on nourishment locations. Like with all beach nourishments, erosion rates increase initially, yet after a few years return to the long-term average. The wider beaches enhance the coastal safety level, the touristic use and resilience with respect to sea level rise.
  10. Over 50 historical elevation maps and over 500 beach profiles of Belgian coast were digitized and made available within CREST project. These have already proven valuable to study the difference in response of different types of beaches to sea level rise and storminess over more than 30 years.
  11. Your data and research methodology might be invaluable for future researchers, document them well.
  12. The uncertainty on the bathymetric surveys has a large impact on the accuracy of the observations. It can be reduced by performing independent terrestrial control measurements of the low-tide area immediately following echo sounding.
  13. The human interventions (dredging in navigation channels, beach nourishments and local interventions by municipalities) should be kept in a well-structured database in relation to the morphological monitoring.
  14. In order to study the morphological relationship between the off-shore and the active coastal zone, the surveyed area should be extended seaward.