Alternative model for piping prediction
The Shields–Darcy (SD) model is a piping model which predicts internal erosion below dikes and the allowable gradient across a dike during high water. In such situations, groundwater flows through sand layers from the river to the polder. This makes the hinterland wet. With a rising water level, the groundwater can also transport sand. If the high water persists for a sufficiently long period, the dikes might eventually fail due to the piping failure mechanism.
The SD model calculates various groundwater discharges and pipe characteristics, such as the critical values of the pipe velocity and pipe discharge. In this piping model, the allowable gradient is determined by two resistors, namely the seepage resistance and the pipe resistance. The seepage resistance refers to the resistance experienced by the groundwater in the sand layer, and the pipe resistance represents the flow resistance in the meandering and braided pipes.