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For predictive numerical simulations of subsurface floods (groundwater head rise due to high water in a contiguous river), it is important to know how to represent the bank storage process in a numerical groundwater model. Whilst leakage approaches are frequently used for modeling bank storage, another option is the application of a head boundary condition. In order to get a better understanding of the bank storage process, we analyze the bank storage event in the Neuwieder Becken (Middle Rhine) in April 1983, which has been reported by Ubell (1987). We found the leakage function to be nonlinear and hysteretic. The evaluation of different model variants for Ubell’s bank storage event shows that both a head
boundary condition and a leakage boundary condition are appropriate modeling approaches. For practical reasons, the leakage boundary condition is preferred. A linear leakage function represents the bank storage process for the analyzed event sufficiently. A hysteretic course of the leakage function can be achieved in a three-dimensional groundwater model by layering the hydraulic soil properties in the vicinity of the bank.