ABSTRACT
Planning and development intrinsically require an approximation of the future, which is often based on the standard of the average and the normal. However, such an approach is not realistic, as it neglects the abnormal and the extreme, both in the physical and human environment. Historical analyses provide a required perspective about the frequency and impact of extreme natural events as well as human-made calamities. It is, therefore, essential that planning for the abnormal and extreme be included in the scope of both regional and national development strategies, particularly with regard to water (Bruins 1996).
