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The picture below gives a global view of wave heights for a return period of 1 year.
As the ERA-interim Interim wave data is based on offshore charactersiticscharacteristics, waves are translated to onshore conditions by comparing the waves from ERA-INTERIM Interim with a depth limited wave. If the depth limited wave height is smaller, this wave height is used for calculations whereas the period is maintained. The wave direction is not taken into account explicitly; the wave direction is assumed to be coast-normal.
Water levels
The water levels, which are a combination of tidal elevation and storm surge, have been chosen rather arbitrarily at 1, 3 and 6 m above MSL. Substantially higher levels occur are likely to occur at some places in the world. For instance, parts of Bretagne have a tidal range of well over 10 m. There, only 1 m of surge is required for MSL + 6m, which seems not extreme. The feeling is that the selected levels are representative of a large part of the world, especially areas near the equator where the application of the FAST tool seems most likely.
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Wave attenuation over foreshores is typically most relevant during storm conditions that create a surge (water level set-up) in combination with high tidal levels. For the MI-Safe tool, a water level that has a probability of occurrence of 10%, i.e. once in 10 years, is considered to be the most relevant: This represents a storm that is both frequent enough to appeal to users (a 1/100 or 1/1000 year condition may seem too extreme) and high enough to be a serious threat to coastal regions. The representative water levels or hydraulic boundary conditions are derived from a global D-Flow Flexible Mesh model (Muis et al., 2016) that includes tides, storms and hurricanes. The output of this model is mapped to DIVA segments, so local anomalies can occur for coasts with irregular shapes (bays, estuaries). More extreme or locally tailored conditions can be studied using the more advanced versions of the MI-SAFE tool, which can take into account hydraulic boundary conditions that are specified by users or derived from dedicated modelling.
Vegetation
Field data (why, how and where with links to deliverables/products) (Iris)
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Surge levels used for the MI-SAFE Expert tool (Jasper, perhaps you can still use some of text below?)
For the Expert version of the MI-Safe tool, locally derived hydraulic boundary conditions have been used wherever available (NL and UK sites) to have the closest resemblance with actual flood defense design conditions.
Wave attenuation over foreshores is typically most relevant during storm conditions that create a surge (water level set-up). For the tool, a water level that occurs once in 10 years was considered to be the most relevant: This represents a storm that both occurs often enough to appeal to the user (a 1/100 or 1/1000 condtion may seem too extreme) and is high enough to be a serious threat to coastal regions. The surge levels are derived from a global surge model (Muis et al., 2016). More extreme or tailored conditions can be studied using the more advanced versions of the MI-SAFE tool.
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