# The Modelling Process and Environmental Impact

• Philip Dyke
Part of the Topics in Environmental Fluid Mechanics book series (EFMS, volume 2)

## Abstract

To the majority, the word modelling still means something to do with photography or, if they have a scientific background, the building of scaled-down replicas that ought to mimic real life situations. In this latter category one thinks of Civil Engineering consultants building models of harbours with attendant breakwaters and jetties, and then subjecting them to a particular wave climate. The way this is done is to build a physical model, usually in a large area reminiscent of an aircraft hanger. In this model, the area of coast or river or estuary (whatever) is built from materials such as concrete, sand and cement. Of course there is a scale, perhaps 1:20 or even larger, which needs to be considered when examining results. If waves are of interest, then there has to be a paddle mechanism included in order to generate them. Exactly how the scale factors can be calculated is the subject of Chapter 2, but suffice it to say that measurements of quantities such as wave height, current speed and direction, the force on pier or jetty can be made on the model. Appropriate scale factors are then applied and an estimate of the real life wave height, current speed and direction, force on the pier or jetty or whatever can then be made. Up to thirty or so years ago virtually all modelling in coastal engineering or oceanography referred to this kind of activity. These days, modelling invariably means use of the computer and the big once national facilities (e.g. Hydraulics Research in the U.K. Delft Hydraulics in The Netherlands both now privatised) now have much scaled down (no pun intended) the facilities for these physical models but have many sophisticated computer models to replace them. Many would prefer the word enhance rather than replace, as there is still the place for a physical model where the carefully placed strain gauge can give information to reinforce the output from a mathematical model. In most cases, the results from a mathematical model implemented via software on a computer will tell the same story as the results from a physical model, but if there are contradictory results, neither should automatically be believed. Perhaps they are both wrong and the situation is more complicated that either model builder thought! Areas where physical modelling is still dominant is in the building of bridges and in the design of spacecraft. In both of these areas, the final costs are so huge that the expense of building a physical model is less critical than for example estimating dilution rates of a dissolved substance in an environmentally sensitive estuary. In this latter case, mathematical models are now almost always used.

## Keywords

Ocean Physic Bovine Spongiform Encephalopathy Ozone Depletion Wave Climate Hard System
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.