Stream Modelling: hydrodynamic model and models for transport and spreading of pollutants

The development of the digital computer has been of great importance for the hydraulic engineer. Through many centuries hydraulic engineering was based on practical know-how, obtained through many hundred years experience. Gradually mathematical theories were introduced and accepted among the engineers, but as the scale and the complexity of the hydraulic works increased, the mathematical models became so complex that a mathematical solution could not be obtained. This created a demand for new methods and again the experimental investigation became popular, but this time as measurements on small-scale models. But still the scale and complexity of hydraulic works were increasing, and soon even small-scale models reached a natural limit for some applications. In the mean time the modern computer was developed, and it became possible to solve complex mathematical models by use of computer-based numerical methods.