Flood Threat in an Area – Topical Natural Hazard

Based on last years experience we can say, that problem of flood threat in an area has already exceeded engineer-hydrological, respectively water economy frame. There are clear indicions, which indicate, that this phenomenon needs a complex view. It means particularly knowledge of run-off relations, which are connected with time and spacial wide spread of rainfalls, but also with land cover and land use. Methodics of identification and evaluation of natural hazards and risks allow such complex view. Problems of consideration of natural processes as factors, which limit or even threat interests of human society is very topical. Also extreme (maximum) basin run-off can be included among such processes. In the first part of presented study, there is a brief review of papers, which deal with such evaluation. An application of methodical advance in a concrete area is presented in the second part. Risk hazard susceptibility vulnerability = + + 90 Acta Universitatis Palackianae Olomucensis Facultas Rerum Naturalium Panizza (1986) deals with evaluation of geomorphological hazard, resp. geomorphological risk. According to the scheme presented in the figure no.1 author pays attention to risk evaluation by natural hazard evaluation, susceptibility and vulnerability of environment. The author applies an analogical advance in the narrower specialized paper (Panizza, 1989) to evaluate seismic risk. The seismic risk map of the USA (fig. 2) was already finished (Costa, Baker, 1981) in 1981. The example of spatial spreading of seismic hazard in selected area is presented in papers Degg (1986, 1987). The results of earthquake hazard in California Hodgson, Palm (1992) are presented as a map outputs. The maps represent not only spatial wide spread of the hazard, but also evaluate changes of settling development, land use, prices of lands and other aspects based on a more years research, which are caused by existence of natural hazards. Volcanic hazard is also connected with tectonic lines, resp. neotectonic movement of earth crust (Cooke, Doornkamp, 1990). Hrnčiarová, Miklós (1991) have been interested in evaluation of morphometric indexes in interpretation of water and material movement dynamic downhill with the aim to propose protection against soil erosion. Juneja (1974) deals with potentional soil erosion as one of hazards. Cartographical illustration of many natural as well as anthropogeneous hazards is included in the work. Hreško (1998 a, b) deals with the soil erosion hazard (and avalanche hazard), too. In the last period, more of papers appear, which deal with evaluation of drought hazard. It is caused by global world tendention of increasing interest in problems of global climate changes, which are simplified and often called as global warming. Papers (Changnon, 1989, Lamb, 1992, Mathews et al., 1994) deal with consequences of such changes in the concrete regions. Papers (Hewitt, 1983, Cross, 1994 a, b) directly analyze relationship between climate changes and man activities in landscape, e.g. agriculture. Presented review of papers is not definite at all. It is compiled in a way to allow sufficient review about wide exploitation of methodics of topical natural hazard identification and evaluation. A cartographical illustration (area maps) of natural hazard, resp. risk connected with it is the most often practical output. 4. FLOOD HAZARD IN THE GEOGRAPHICAL