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

In test T3 of the Deltflume H298 series \citep{Steetzel1987} erosion above medium height dune revetment is ivestigated. The test was carried out at a depth scale nd = 5 \citep{Vellinga1986} and the initial profile in the flume correponds to the reference profile for the Dutch Holland coast. At the dune foot (located at x = 193 m from the wave board and z = 3.80 m above the flumes floor) a concrete revetment is applied that partly covers the dune face (slope of 1:1.8). The lower end of the revetment is located at z = 2.5 m and the top end at z = 4.8 m. The test was conducted with a constant water level (set at z = 4.2 m) and wave conditions that correpsond to a Pierson Moskowitz spectrum with Hm0 = 1.52 m and Tp = 5.37s. The sand applied in the test has a median grain diameter ($D_{50}$) of approximately 210 um.

Simulated and measured profile development during T3 are compared in (\autoref{fig:DeltaflumeH298_T3_fig1}). In the physical experiment the eroded volume above the revetment is $10.37 m^{3}$ and at the toe of the revtment a scour hole devlops till a depth of z = 0.92 m above after seven hours simulation (is 1.21 meter below the dune foot). Without any relevant model improvements it is concluded that XBeach underestimates the erosion volume above the revetment and the erosion depth at the toe of the revetment. Considering the limited erosion volume above the revetment it is hypothesized that in addition to long wave run-up also short wave runup should be included in the avalanching algorithm (which is the main mechanism to release sand from the dunes). As mentioned before in test T1 a reasonable explaination for the underestimation of the scour depth at the toe of the revetment may be found in simulated sediment suspensions in the proximity of the revtment, which are underestimated with a factor two ((\autoref{fig:DeltaflumeH298_T3_fig2})). The simulated mean flow is supposed to be in reasonable agreement with measurements. 

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${tools.image('DeltaflumeH298/T3/', 'fig2.eps')}