Geological framework for assessing variability in subsurface piping parameters underneath dikes in the Rhine-Meuse delta, the Netherlands

Dike failure due to piping – concentrated flow of seepage water underneath the dike during periods high flood levels has been recognized as a major component risk. Simulation models predict in risk assessments require detailed information on subsurface characteristics such sediment grain size and thickness overburden layers. Quantitative local determination these poses challenge natural environments with heterogeneous substrate. Geological knowledge genesis resulting structure may provide useful spatial variability substrate characteristics. When correctly implemented, available geological can for a-priori identification sections which is susceptible (strategic new data collection), a-posteriori screening collected field (identifying unexpected values). In two ways it potential reduce uncertainty parameter estimates calculations that determine occurrence at specific site. Here we describe framework using assessments. Based existing digital mapping products development Rhine-Meuse delta, first compiled map distinguishes primary hydrologically relevant units: upper main aquifer sands (pre-deltaic subunits), topped by deltaic wedge aquitard dissected channel belt sand bodies (deltaic subunits). We then used divisions an analysis borehole (>130.000 locations, UU-LLG dataset), quantitative sizes very top non-sand thicknesses, split per subunit summarized sub regions (lower central delta rim sectors). This enables us demonstrate what extent median deposits varies within delta. quantitatively determined (1) delta-scale longitudinal downstream fining trend drops stream power through changes gradient erodibility, (2) pulsed variations associated uptake reworking pre-deltaic sediments belts. Although tailored utilizing substantiation grouping be transposed applications elsewhere. regionalization plain greatly help streamline acquisition, anticipating growing availability medium density datasets increasingly urbanized deltas managed rivers around world.