Zur gekoppelten numerischen Modellierung von unterirdischem Hochwasser
A subsurface flood is defined as a groundwater head rise induced by high water in a river. While in the river the flood wave decays comparatively fast, the duration of the subsurface event is usually longer. Substantial unfavourable consequences of the underground flood is damage to buildings and infrastructure caused by increased uplift forces and the penetration of water into buildings. At the surface, the water movement can be mathematically described by the Navier-Stokes equations or simplifications of these equations. As a programme to model the movement of water on an inundated area, Ilmoflood is presented. For the subsurface, the Richards equation and the groundwater flow equation are appropriate. The Feflow groundwater simulation programme solves these two equations numerically. Between the water at the land surface and groundwater, bank storage, infiltration of water from an inundated area and return flow act as interchange processes. Thus, in order to predict the subsurface flood propagation, it is necessary to couple a surface flow model with a groundwater model. One focus of this dissertation work is the model coupling of Feflow and Ilmoflood with the OpenMI standard. The main challenge was to implement this standard into the commercial programme Feflow without changing the source code. This has been achieved with the help of network programming methods implemented into the Feflow programming interface. It is now possible, to use groundwater models already existing, which for example have been developed for water supply purpose, for the planning of flood protection measures. Against this background, it is investigated how the interchange processes can be modelled best with the available programme functions. For the bank storage process, field data from the literature for one subsurface flood event is analysed and in addition, numerical model investigations are carried out. The infiltration process is analysed with the help of analytical infiltration models and the numerical solution of the Richards equation. For the return flow, modelling aspects are discussed. Key findings are, that the bank storage can be modelled well with the existing leakage boundary condition in a groundwater model. For the vertical infiltration from an inundation area, leakage approaches are a simplified representation of the process, but considering these limitations, they are appropriate for the objective of this investigation. Several application cases are presented to give a better understanding of the subsurface flood processes and to explain, how the model coupling works.
info:eu-repo/classification/ddc/620, Hochwasser, Grundwasser, Infiltration, Ingenieurwissenschaften, unterirdisches Hochwasser, Qualmwasser, Uferspeicherung, OpenMI, subsurface flood, leakage, bank storage, Feflow
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