Zoning
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ZONING Philipp Schmidt-Thomé1, Stefan Greiving2 1 Geological Survey of Finland (GTK), Espoo, Finland 2 TU Dortmund University, Dortmund, Germany
Synonyms Outlining; Planning; Regulation Definition Natural hazard zoning is the division of any determined space into areas which could be affected by hazardous phenomena to variable degrees. Discussion Zoning is used as an instrument in land use planning to regulate land use in areas affected by specified hazard patterns. Usually, the determination of hazard zones vary gradually from imminent hazard zones, with very restrictive land use or determined building regulations, toward zones that are considered outside the statistically relevant reoccurrence or magnitude of a given hazard, which do not require land use regulations that pay special attention to a defined hazard. There are different national approaches on the definition and the use of hazard zones. The legal binding of hazard zones depends not only on the potential occurrence of hazards, but also on land planning regulations and respective responsibilities in the case of the occurrence of a hazard. In some countries, a municipality issuing land use plans can be held responsible in the case of a natural hazard, whereas in other countries the land developer has to ensure and guarantee safety. Hazard zoning aims mainly at influencing or avoiding future developments in affected areas, but is less effective for existing structures due to private property rights.
For that purpose, there are different options in the insurance sector. In some areas, official hazard zones and respective risk patterns of insurance companies do not match, whereas in other countries legal institutions tightly cooperate with the insurance sector. Since the second half of the twentieth century, hazard maps have increasingly been incorporated into legal acts that regulate land use, for instance, in Austria and Switzerland, hazard zones related to avalanches have been mapped since the 1960s and following legal regulations were installed officially as a practice in the 1970s. The rapid rise of costs related to damages caused by natural hazards since the 1990s have led to an increase in national activities to regulate land use in hazard-prone areas. This development is in line with a continued population pressure and land take toward hazard-prone areas, a general understanding that natural hazards cannot be fully mitigated by technical means, as well as growing demands from the insurance industry to lower vulnerabilities related to hazards. The determination of hazard zones depends on the nature of a hazard. In the case of avalanches, usually return periods, maximum run out extensions, and magnitudes are used to determine the borderlines. Mass movements (landslides, rock falls, soil creep, etc.) are influenced by many factors such as the steepness of slopes, the underlying geology, potential run out areas, and shear zones. Flood and storm surge hazard zones are also related to reoccurrence, e.g., 100 year floods, the potential depth of inundatio
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