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MI-SAFE tool results: conditions, confidence, context and sensitivity

Expert functionality

For the FAST fieldsitesfield sites assessed in the Expert version of MI-SAFE, the 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.

The 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 data for bed level, a simple translation of ERA-Interim waves and GTSM surge levels to nearshore and vegetation properties based on standard vegetation types.

 

Educational functionality

The conditions tab (Figures 2 and 24) displays the local bed level perpendicular to the coast with the intertidal part highlighted

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The context tab describes and quantifies the conditions at the site (e.g. vegetation type encountered, length of vegetation covered), 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. 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 in the Expert version shows how different return periods and different vegetation densities (bare, sparse, standard and dense) affect the required crest height. Note that this is the required crest height with respect to still water level (surge), not with respect to MSL. The Educational version does not have this functionality.

The case study sites

In the figure below, Figure 25, the location of the FAST case study sites are shown. In each red box, two locations are selected, leading to a total of eight case study sites in four countries. 

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