Loads of Water Defenses

This project is about determining extreme winds, water levels and wave conditions that the Dutch primary water defenses should be able to withstand.

The Dutch safety levels (figure 1) are based on how often we accept water levels and wave conditions that exceed the Hydraulic Boundary Conditions (HBCs). Water defenses in, e.g., the most densely populated areas in the west of the Netherlands should be able to withstand water levels and waves that occur once in 10,000 years[i].

This project is divided into 3 work packages:

WP1: “The use of high-resolution models in the determination of extreme wind fields”. Baas [1] concludes that the operational weather model HARMONIE is able to provide realistic (in time and space) wind simulations for 17 historical storms and that it is possible to simulate the whole ERA-Interim period (1997-2013) with the same model configuration and quality. 

WP2: “Database of high-resolution model results for the determination of the HBCs”. In WP2 Van den Brink [2] concludes that for open water HARMONIE produces realistic (in time and space) wind simulations for the whole ERA-Interim re-analysis period (1979-2013), for both wind speed and MSLP. For inland waters, such as lakes and rivers, HARMONIE mostly underestimates extreme wind speeds, but it is understood why and can be corrected for. Overall, the wind climatology based on the HARMONIE simulations is realistic enough to be used as input for WP3.

WP3: “Extreme value analysis of the high-resolution model 10-m wind fields”. Van den Brink and Caires [3] show that, based on the high-resolution model winds, reliable and consistent estimates of extreme water levels and waves can be made.

[i] In the future the normative values in figure 1 will change because they will be related to the probabilities of failure of dike rings instead of the probability of exceedance of hydraulic loads (waves/water levels).

Figure 1: The safety standards of the Dutch primary water defenses. According to the Dutch Water Act (Waterwet, 2009) the safety of the Dutch primary water defenses must be assessed every six years (2011, 2017, ...).
Figure 1: The safety standards of the Dutch primary water defenses. According to the Dutch Water Act (Waterwet, 2009) the safety of the Dutch primary water defenses must be assessed every six years (2011, 2017, ...).
Figure 2: 10,000 return value estimates of the wind speed at 10 m height for Southwest, Northwest, Northeast and Southeast directions.
Figure 2: 10,000 return value estimates of the wind speed at 10 m height for Southwest, Northwest, Northeast and Southeast directions.

The SBW program

The general objective of the SBW program (“Sterkte en Belastingen Waterkeringen” or “Strengths and Loads of Water Defenses”) is “To fill the most important knowledge gaps in order to achieve a better estimate of the safety against failing of the primary sea and flood defenses” [4,5,6].

SBW-Belastingen is one of the projects in the SBW program related to hydraulic loads on the primary water defenses. The general objective of SBW-Belastingen is “To determine the quality of models and methods and improving them where needed, in order that in 2011 and onwards more accurate HBCs can be determined”.  

The SBW-Belastingen project has a direct relation with the WTI-project (Wettelijk Toets Instrumentarium or “Statutory Safety Assessment Suite” project). The WTI-project is responsible for the delivery of the HBC and rules on how to apply them in the assessment of the water defenses. SBW provides expertise and instruments for the WTI project.

 

[1] Baas, P., 2014: Final report of WP1 of the WTI2017-HB Wind Modelling Project. KNMI Scientific Report; WR 2014-02 (http://www.knmi.nl/bibliotheek/knmipubWR/WR2014-02.pdf), August 2014.

[2] Van den Brink & I. Wijnant, 2016 A 35-year high-resolution meteorological dataset for The Netherlands Final Report of WP2 of the WTI2017-HB Wind Modelling project. Technical Report KNMI/Deltares.

[3] Van den Brink, H.W. and Caires, S. 2015, `Extreme wind statistics for the Dutch primary water defenses', Technical Report 1220082-007 KNMI/Deltares. Final Report of WP3 of the WTI2017-HB Wind Modelling project

[4] Groeneweg, J., Burgers, G., and Caires, S. 2012. `Adjusted Planning SBW Wind', Technical report RWS.

[5] Groeneweg, J., Burgers, G., Caires, S., and Feijt, A. 2011a. `Plan of approach SBW wind modelling. SBW - Belastingen', Technical Report 1202120-003 Deltares.

[6] Groeneweg, J., Smale, A., Dongeren, A. Van, Luijendijk, A., Beckers, J., Diermanse, F., and Caires, S. 2011b. `SBW Hydraulische Belastingen. Projectplan 2011', Technical Report 1203757-000-Hye-0007-v3 Deltares.