General Aspects of Construction and Execution of Hydraulic Modelling for Flood Runoff in Rivers
Hydraulic models for water management including of course flood management are essential tools for designing and analyzing of facilities, which ensure adequate flood protection without wasting financial resources through over-design or poorly conceived designs. Currently hydraulic models are integrate in concept of hydro-informatics, complex modelling and information systems for water management, which contain hydraulics, hydrology, environment engineering and use advanced information and communication technology, supported by computer- based tools (Abbott, 1979; Tagelsir, 2010). Hydroinformatic tools, including Computer-Aided Design (CAD) programs, Graphical User Interface builders, Geographic Information Systems (GIS), Hydrodynamic Modelling Packages, Code Builders, Databases, Data Analysis and Communication Tools and are used to provide support for decision making for flood and river management, urban drainage and supply systems, at all levels of management and operations providing answers among other to the following questions (Chow, 1959): - what are the most appropriate modelling systems and tools? - how to construct reliable models of the water-based systems? - how should these models be integrated into decision support systems that would help engineers and managers? Nowadays no water- related projects can be executed without hydraulic modelling supported by computer- based tools i.e. Hydroinformatic tools. It should be also noted that a Modelling Systems Development is the full life cycle development of software tools from their initial conception and mathematical basics, design, software implementation, to verification and the end-user implementation. The most important steps to building complex hydraulic models for water and flood management of riverine systems can be shown in Figure 1.
Figure 1.
Principle schemes for construction and execution of models
The first and very important step, to build models, is the Technical description of the physical system including usual simplified schematizations of the complex real riverine system and as well the mathematical description of the flow in river. The technical-description of the physical system i.e. the river system is necessary to prepare his modelling based on extended Hydroinformatic tools. The simplified schematizations of real flow systems are necessary, to highlight the conditions under which the solving of problems with technical interest is accomplished by modelling using simplified schemes of the real flow system: one-dimensional (1D), two-dimensional (2D) or a combination thereof (e.g. 1. 5 D).The mathematical description of the physical system includes basic definitions like continuum concept, physical variables and parameters and mathematical representation of the fluid body and his motion and so on and are necessary to write the fundamental equations of hydrodynamics as theoretical basics for the modelling. For the simplified schemes, the corresponding particular forms of the general equations and specific forms are presented and the initial and boundary conditions are specified, which together form the so called mathematical formulation i.e. the mathematical model of the technical problem to be solved. To solve these mathematical models, numerical methods will be applied, beginning with methods of discretization, continuing to formulate finite difference equations, formation of linear equations systems corresponding to main numerical methods such as Finite Difference Method, Finite Volume Method, Finite Element Method etc. and ending with a schematic presentation of the complete achievement of numerical models (software), including pre - and post-processing. To illustrate the construction and application of numerical models with the above explanation, a briefly description of some known hydrodynamic/hydrological models such as DUFLOW, HEC-RAS, MIKE-11/21, is included as well, in the last part of this chapter, which are effective applications of several representative case studies in modeling and simulation of hydrological processes.