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The MI-SAFE viewer enables via WPS data retrieval over the profile via OGC services. To acquire these data for a queried location (point), the tool first determines a transect perpendicular to the nearest coastline. This transect runs 1000 m inland of the point where the bed level equals MSL and 1000 m seaward of this point; the area of interest where most wave attenuation occurs. This data is then used to query a pre calculated table of model results. The wave attenuation thus obtained is compared to the wave attenuation over a similar but bare transect. The result is shown indicating whether or not vegetation is existent in the intertidal and/or contributes to wave attenuation; the criterion for the latter is whether the situation with vegetation causes 20% lower waves than without vegetation.
MI-SAFE
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viewer results:
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Conditions,
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Confidence,
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Context and
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Sensitivity tabs
For the FAST field case study sites assessed in the Expert version of MI-SAFE, the conditions Conditions tab displays the bed level from local sources (e.g. DEM), the local water level (from local or regional hydraulic boundary conditions), the vegetation cover (from EO) and the change in wave height (from site-specific XBeach calculations) from offshore to the levee. In the Educational version, the same type of parameters are displayed but the bed level, waves, surge, vegetation type and cover come from global sources and the attenuated wave height comes from the closest match with schematized conditions in a look-up table with XBeach pre-calculated results.
The confidence Confidence tab, similar in nature but different in contents for the Expert/Educational versions, indicates the origin of the various data sources (bathymetry, topography, wave height, surge or water level, vegetation presence and vegetation properties) by mouse-over and the confidence associated with these sources. The confidence is expressed in colours and linked to the detail, accuracy and particularity of the information:
- Green implies the highest confidence, typically for local DEMs based on LiDAR, local hydraulic boundary conditions and local LAI maps that account for spatially varying vegetation properties.
- Orange stands for e.g. TEA topography, hydraulic boundary conditions that apply to larger stretches (regional; multiple kilometers) of coastline and vegetation presence from EO combined with locally observed spatially uniform vegetation properties.
- Red means SRTM or GEBCO global data sources for bed level, a simple translation of ERA-Interim waves and GTSM surge levels to nearshore and vegetation properties based on standard vegetation types.
The context Context tab describes and quantifies the conditions at the site (e.g. vegetation type encountered, length of vegetation field covered) , and the hydraulic boundary conditions used (surge and wave height). This tab also compares the wave height in case of a vegetated foreshore with that on a bare foreshore and quantifies the required crest height for both situations, effectively giving an indication of the effect of vegetation on waves. For the Educational version, the required crest height is only calculated using the strictest overtopping criterion (q=0.1 l/m/s), for the Expert version also the required crest height using a less strict overtopping criterion is displayed to highlight the sensitivity of the results for this criterion.
The sensitivitytab Sensitivity tab in the Expert version shows how different return periods (10, 100 and 1000 years) and different vegetation densities (bare, sparse, standard and dense) affect the required crest height of a (potential) levee. Note that this is the required crest height with respect to still water level (surge), not with respect to Mean Sea Level (MSL). The Educational version does not have this functionality.
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