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SBW Field Measurement Programme

Bart Spelt (1), Herman Peters (2), Ivo Wenneker (3), Magiel Hansen (2), Andre Jansen (2), Hans Miedema (2), Peter verburgh (2), Albert Huisman (2), Paul Kramer (2), Marco Peters (2), Arjen Ponger (2)

 

In compliance with the Dutch Water Act (‘Waterwet, 2009’), the safety of the Dutch primary sea and flood defenses must be assessed every six years for the required level of flood protection. Filling the most important knowledge gaps (Dutch: ‘kennisleemtes’) in this assessment forms the objective of the SBW (‘Strength and Loading of Water Defenses’; Dutch: Sterkte en Belasting Waterkeringen) programme.

 

In this assessment, Hydraulic Boundary Conditions (water levels and waves) are required. They are determined on the basis of extrapolation of offshore wind, waves and water level conditions to extreme conditions, combined with the transformation of wave conditions from offshore to shallow water near the water defense structure using the SWAN spectral wave model.

 

Validation material for SWAN is obtained in the SBW field measurement programme. Since 2004, this programme carries out field measurements during each storm season in the following areas:

  • Dutch Wadden Sea: a complex area enclosed by a series of barrier islands and the Dutch mainland coast, featuring ebb tidal deltas, tidal channels and shallow tidal flats.
  • Petten sea defense: a bathymetric profile typical for the open dutch coast, starting offshore (> 20 m deep) gently sloping, including some sand banks, towards the dike.
  • Lake IJssel: a large (20 x 60 km2) and relatively shallow (~ 4 m deep) lake.

 

Waves are measured using buoys and instruments installed on measuring poles. The use of X-band radars to obtain spatial wave and current data is under investigation. In addition, the essential SWAN input quantities (seabed topography, water level, wind and currents) are measured as well. Furthermore, at the Petten dike specific instruments have been installed to measure wave run-up and wave overtopping.

 

The presentation and paper give insight in:

  • the three measurement sites (which instruments are employed where and why),
  • experience with the instrumentation and site logistics, and
  • how the data is processed and disseminated