Vízügyi Közlemények, 2001 (83. évfolyam)

2. füzet - Rövidebb tanulmányok, közlemények, beszámolók

308 Nagy L.—Tóth S. The map of risk is a special topographic map, which show the probabilities of occurrence along with the caused or expectable damage. A special risk map is the flood-risk map, which is the basis and starting point of all development policy or flood control policy. These maps do not depend on the occurrence of actual events and their in-time validity is restricted. Namely, one must not forget that about 40 % of flood damages can be explained by the disregarding of risk factors. The basic task of making risk maps are as follows: — Provision of initial information for planning land uses — Determination of damages caused by the flood — Estimation of advantages achievable by reducing the risk — Decision support — Accurate estimation of the feasibility of non-structural flood-control measures, such as the flood-resistant construction — Provision of the basis for any insurance plans — Provision of the logical basis of planning investments and estimating priorities, with special regard to non-structural measures — Showing realistically the dangers to the population The flood-risk map is also suitable for making a special test, as it provides an estimate of the expectable future events on the basis of past flooding events (inundations due to levee breeches). If these inundations have been recorded in appropriate quantity and with appropriate accuracy, then one is able to make the map of zones and the maps of risk. It may be stated that these results have extremely good empirical value, although the flood-risk maps provide much more information than the map of some individual inundation. Namely, in the flood-risk map the flood-zone maps are combined with damage data, as it follows from the definition of risk. In Hungary (where 97% of the former flood prone areas were brought under protection) the method and scope of flood-risk mapping from that of the American and West-European practice, which latter deals mostly with open land-prone areas. Nevertheless, it should also be pointed out that with the transition to market economy and with the transformation of ownership structures in Hungary, and also with the splitting of earlier large-scale industries, one should also take into consideration the making of risk maps for the protected flood-plains (flood-berms) and also for the valley-bottom flood-plains of smaller streams. This latter is even more justified, since in Hungary more than 1,500 settlements are crossed by small streams, which represent flood risk to a large part of the inner area of these settlements. To this end one should remember of the recent floods: those of 1988 of the River Zala, 1990 of the stream Parádi-Tarna, the floods of the Tama and Kemence and other streams.