Urban flash floods

The menu navigation in the itwh software package “Urban flash floods” is workflow-oriented: All required tool are included, starting with the data preprocessing as well as the automated creation of the calculation model up to the visual evaluation of the results.

• Separate data management: FOG 7 supports the management of initial data required for the creation of 2D models. Geometric input data for the automated model creation, i.e. buildings and breaklines as well as the position of street inlets, are managed in a geodatabase in order to be immediately available for the creation of various model variants. As known from HYSTEM-EXTRAN 7, the administration of sewer system related data takes place in the model and result data base *.idbf.
• Hydraulic 2D surface runoff model: Instead of a simplified hydrological model, an extensive surface runoff calculation, on the basis of 2D shallow water equations, is used. The equations are solved by means of the extremely stable Finite Volumes method.
• Smooth 2D model creation: The extensive user support encompasses for example the data import, the data tailoring for the area to be modeled, the allocation of attributes, such as roughness and overflow depths, as well as the linkage of the hydraulic sewer system model with the 2D surface model.
• Topologically consistent input data: Via a preconfigured topology assessment the data is examined concerning its suitability for the automated model creation.
• Exact configuration of the model generation: The automated model generation may be configured via the parameters so that the level of detail and the degree of smoothing of the elevation data can be specified in the elevation data model.

The sewer system model and the 2D surface runoff model are coupled together. The coupling takes place at the manholes and street inlets. As a result of the linkage of both models, in conjunction with the extensive calculation approach, a realistic model is formed. In contrast to other hydrological models, depressions and hollows are implicitly considered.

Various versions of the sewer system- and 2D surface runoff model may be combined for the simulation of planning options (the use of linkage manholes with the same name is a prerequisite).

The calculation approaches of HYSTEM-EXTRAN 2D are visualized in FOG 7. The water levels may be displayed in a chronological sequence for the output steps. The chronological sequence of the simulated flood may also be displayed as a video clip (*.avi file).

…the software package “Urban flash floods” naturally takes into account the conventional guidelines, such as the DWA working paper A 119 and the DIN EN 752.