Simulating moving boundary using a linked groundwater and surface water flow model

The moving boundary problem is a very important phenomenon in shallow water flows over wetlands and floodplains, particularly with regard to flooding. In considering the natural linkage between surface and groundwater flows for practical studies a new integrated surface and groundwater flow model has been developed for predicting shallow water flows, with particular emphasis being given to its capability in dealing with moving boundary problem. In linking a surface and groundwater model, a hydrostatic pressure distribution is assumed to enable the water surface gradient to be used as the driving force for the groundwater flow component of the model. The linked surface and groundwater flow model is capable of treating the moving boundary problem naturally and implicitly, without any specific algorithms being used to deal with the flooding and drying processes explicitly. Four typical numerical tests have been undertaken to study the performance of the new model with particular attention being focused on checking the accuracy, robustness and mass balance of the model. The numerical results show that: (a) the model is capable of treating moving boundary problems effectively without causing any substantial problem for mass conservation, and (b) the model is capable of giving reliable and accurate results.