<%namespace name="tools" file="tools.tex"/>

In this test, retreat distances obtained from DUROS+ and XBeach using a selection of JARKUS profiles characteristic for the Dutch coast are compared \citep{DenHeijer2011}. The comparison is presented in \autoref{fig:DUROS_RD_durosp_xbeach}. The retreat distance is defined as the horizontal distance between the NAP+5m contour and the erosion point. The erosion point is defined as the first diversion point between the pre-storm and post-storm profile, when going from the land side in seaward direction. Diversion is considered as a vertical difference of more than 5cm.

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In terms of safety, we see that DUROS+ is more conservative in case of larger retreat distances, with a lower frequency of occurrence. For smaller retreat distances, with a higher frequency of occurrence, XBeach is more conservative. As we have seen in other tests, in mild near-equilibrium conditions, XBeach shows in general more erosion than measured. These observations are in agreement with the comparison with DUROS+. In storm conditions, however, the erosion prediction is more precise. This behavior is aimed for in dune safety assessment, where DUROS+ functions as a first estimate and XBeach functions as the advanced alternative in case DUROS+ assesses a specific transect as insufficiently safe.

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${tools.image('DUROS/', 'RD_durosp_xbeach.png', 'Scatter plot of retreat distances obtained from XBeach and DUROS+ (blue circle) and XBeach and D++ (green cross).')}
