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Flood Protection on Torrent Flows in Croatia -Prevention of Natural Disaster

There are many causes of flood appearance like: strong rainfalls (short-term and long-term), melting of accumulated snow, collapse of banks previously formed by slides, collapse of constructed dams and banks, water regime changes and coincidental appearances of high waters in the main stream and its affluent, formation of ice barriers in rivers, arresting and accumulating of timbers because of inadequate throughput of bridges etc. Floods are the third greatest cause of material losses in the world, right after earthquakes and tropical storms. With the development of civilization, modes and appearances of harmful effects of water and floods are more expressed. It can be distinguished: floods of great water streams and floods of torrent water streams. Floods endanger not only developing but also developed countries (Germany, Italy, France, Slovenia) Article 86 of Croatian – National water regulation declares that for the purpose of prevention of floods and harmful effects of flood waters, protective water buildings are constructed and maintained, protective procedures and measures for the defense from floods are performed. The defense from flood can be regular or exceptional. Regular or exceptional defense from flood is proclaimed when water level reaches height determined by the plan of the defense from flood with expected further water level increase. Then Article 93 declares that torrent flows are those flows that appear occasionally or permanent flows that under the influence of rain or snow melting are characterized by abrupt changes in water flow that can result in endangering of life and health of humans, assets and disturbance in water regime. Torrent flows, because of strong erosion processes endanger bigger urban settlements, industrial plants, highways, regional routes and melioration systems. Main features of torrent floods are: sudden formation of water wave, propagation (spreading) of frontal water waves through water beds, soil erosion and slides, transport of great amounts of torrent material (soil, timbers, trash, etc.). Croatian National water regulation in its Plan of the defense from floods contains: measures that should be performed before and in case of flood threat, water level at which, at certain sectors, begins regular or exceptional defense, determinations of the equipment and material that should be prepared, legal persons that conduct the defense from flood and names of expert organizers that conduct the defense from flood. But at torrent flows, because of the rapid propagation of water waves, it is almost impossible to conduct measures specified in National water regulation. Therefore I would like to emphasize that present legal regulations in Croatia are not applicable on torrent flows. So, what helps in these situations? Hidrotechnical structures and other works as preventive measures: arrangement of catchment area (biological and construction works), reduction of water wave peaks by construction of retentions or accumulations (multipurpose accumulations) and water regulation through construction of necessary buildings (stairs, banks… ).

Strong rainfall; water regulation; torrent flood; accumulation

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