Vízügyi Közlemények, 2004 (86. évfolyam)

3-4. füzet - Orlóci I.-Szesztay K.: Árvízi kockázat a Tisza vízrendszerében

420 Orlóci István - Szesztay Károly Essentially the controlling of flood risk is an infrastructural service (of the community or the state or an individual). The Hungarian principle of flood control and the system of objects behind it are the result of centuries long historic development and it offers equal level of safety for all interested parties of the flood-prone areas of the rivers against the 100 year floods. Nevertheless, the flood events of the turn of the Millennium have questioned these principles. In the development of the flood control system of the Tisza Valley the key issues include the differentiation of risk levels (at the levels of individuals and for different flood basins), the handling of the contradictions of the principle of equal safety, and the determination/ selection of the risk level undertaken. With the increase of the number of the flood-damage events it becomes more and more obvious that expenditures highly exceed the value of the loss of wealth and the loss-of-safety feeling of the population reaches political levels. In the year 2000 the Government ordered the carrying out of investigations within the flood control programme "Vásárhelyi Plan Update". These investigations were to clarify the requirements of being able to enhance the passage of extreme floods without causing damages. The solution to be proposed (in addition to strengthening the dikes) was to secure the safe conveyance of flood flows, which exceeds the "design flood level" of the Tisza by not more than one metre and secures that of all other floods that cause the risk of dike failure. The solution shall also provide for the increase of the flow conveyance capacity of the flood-channel and shall be in conformity with the landscape management and nature conservation development objectives of the region. It is justifiable that the planners focussed at the localisation (halting-restricting) of inundations and on the emergency storage experiences. Eventually they have also analysed other means of enhancing the control of floods (Table Г). Considering the present and foreseeable future conditions the most feasible means of ensuring the passage of Tisza river floods without causing damages are related to the impounding-recession capacities of the large flood-channel within the levees (Figure 19). The expression "flood-risk" refers to the social reflection of a natural phenomenon. In controlling flood risk one may use the foreign experiences but we must consider the very special Hungarian conditions and the expectable trends of their development. The marriage of something new with that of the living past is a clever decision, as stated by István Széchenyi who initiated and enhanced the regulation of the Tisza Valley.