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The global check as implemented in D-Flow Slide is based on the assessment schema described in VTV-2014 and may comprise the following steps comprises the following steps, which are strongly based on Annex 9.4 of the VTV-2006.
Step 1a : Would flow slide lead to damage on levee (i.e. is the "schadelijksheidscriterium" met)?
The criteria of harmfulness damage criterion ("schadelijksheidscriterium" in Dutch) is met if at the so-called assessment level is situated within the slope (i.e. on landward side of) ("beoordelingsniveau") the actual slope lies landward of the so-called observation profile, in accordance with called assessment profile ("signaleringsprofiel"), see Figure below, which is adopted from Annex 9.4 of the VTV-2006.
1) Determination of
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the assessment profile
The required margin (the horizontal part from the outside toe of the dike) depends on the presence of a revetment and is determined by the relation:
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Honbest is the depth of the channel below the revetment.
Mbestorting is the horizontal projection of the length of the revetment.
In case no slope protection is present, if over the entire channel depth softening sensitive sand is present, this margin is thus equal twice the fictive channel depth (M = 2 H).
The inclined part of the observation profile in line with the horizontal portion. The inclination of the slope depends on the channel depth:
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Step 1b: Criterion on slope protection met (<1:2,5)?
Directly The slope directly in front of the toe of the dike or on the outside of the toe dumping or to the outward end of a dumping, the slope 1or outer boundary of the slope protection, may not cut a 1:2.5 may not be cut by the profileslope that starts at the toe of the dike or outer boundary of the slope protection respectively.
This check should be performed only if the criteria on harmfulness the damage criterion (step 1a) is not met (i.e. a flow slide does not lead to damage). The result of this check has no influence on the result assessment.check will not lead to failure of the safety assessment, but is an indication that maintenance work is required.
Step 1c: Artificially underwater installed and non-compacted sandy foreland ?
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In case of natural deposited slopes, go to step 1d.
Step 1d: Flow slide possible based on the
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occurrence criterion of "the steepest slope over 5 m" ?
If the previous step (step 1c) has not been passed, a check on criteria the first of two occurrence criteria (“optredingscriterium”“optredingscriteria”) must be performed.
The occurrence of flow slide is possible if the following condition is met: the average slope is steeper than or equal to 1:4, over a height of at least 5 m.
If the criteria of this occurrence is criterion is met, both Global and Overall checks FAIL and it should be switched to Advanced methods.
If the criteria of occurrence is not If this occurrence criterion not met, go to step 1e.
Step 1e: Flow slide possible based on average geometry ?
If the previous step (step 1d) has not been passed, the second occurrence criterion a check on the average geometry must be performed.
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