Accordingly, no sensible reason to change from the Classic to the FM approach in urban flood modelling could be found. Additionally, the required workload to set up the FM model was found significantly higher compared to the Classic model. Too low values of this parameter caused instabilities in the program. This was assessed to be the consequence of a parameter, only existing in the FM model, which suppresses the momentum equations of the model and by doing so, retains water in the mesh elements and prevents it to flow unimpeded until a certain depth is achieved. However, the spatial and volumetric distribution of the water in risk areas is more severe in the Classic model’s results. The results showed no significant difference between the models regarding where water generally will flow and accumulate.
As no calibration data was available for the sites investigated at this kind of extreme event, the results only relate to each other. The main investigations have been conducted in scenarios representing a rainfall event with a return period of 100 years. The results have been compared to those obtained from the Classic model, which represents the current method employed to perform these kind of analyses. In this report, the suitability of applying the FM version in precipitation-related urban flood modelling purposes has been investigated. This allows for an increase of the mesh resolution in the proximity of structures that are assumed important for the flood propagation, and a decrease in homogenous areas that are not expected to be as important regarding the general flood distribution. In contrast to the Classic approach, the FM description allows for an altered resolution within the study area. The Classic version employs a structured orthogonal mesh to describe the topography/bathymetry of the computational domain, whilst the FM version bases its general domain description on a triangulated, unstructured mesh. MIKE 21 comes in two versions, the Classic version and the Flexible Mesh (FM) version.
#MASTER MIKE 21 SOFTWARE#
By utilizing advanced numerical hydraulic models, risk areas in the urban environment can be identified and important flow paths can be detected.Ī computer model that is able to simulate the two-dimensional surface runoff is MIKE 21, a part of the MIKE by DHI software series for water environment modelling. An important tool in this process is flood modelling. Such measures include physical planning of the townscape in terms of avoiding water to pond in inappropriate places. Due to recent summers’ amplified frequency in intense rainstorm events, so-called cloudbursts, in places of the world not normally prone to such extreme weather phenomena, interest has aroused amongst authorities regarding measures to address in order to minimize the devastating impact of the subsequent floods.
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