Fuzzy logic application in compiling multi geohazards macro-zone maps; case study: Rahdar, 1:25,000 Quadrangle, Khuzesta
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ORIGINAL PAPER
Fuzzy logic application in compiling multi geohazards macro-zone maps; case study: Rahdar, 1:25,000 Quadrangle, Khuzestan, Iran Hamidreza Ramazi & Amin Amini
Received: 31 October 2012 / Accepted: 1 April 2013 # Saudi Society for Geosciences 2013
Abstract This paper is devoted to describe a new method of fuzzy logic applied to multi geohazards macro-zone maps. The basic steps are (1) compilation of macro-zone maps for each type of geohazard phenomenon. Each phenomenon is then assigned one of seven geohazard zones: very low, low, relatively low, moderate, relatively high, high, and very high; (2) definition of a membership function using a fuzzy logic algorithm to quantify the qualitative data, estimate a geohazard grade for each mesh point, and to convert qualitative maps to quantitative maps; (3) computation of the summed hazard grade for each mesh point and creation a cumulative geohazard map; and (4) compilation of a multi geohazards macro-zone map by defining a mathematical algorithm and again using fuzzy logic. The paper also describes a mechanism that takes subjective engineering judgments into account. Finally, a geohazard map with a scale of 1:25,000 (Rahdar district, Khuzestan, Iran) is compiled. This study divides the area into seven geohazard macro-zones. Zones of high and very high geohazard classification cover most of the area due to the large number of sinkholes and asymmetric subsidences, rock falls and other slop movements. Low and very low hazard zones only cover small localities. Keywords Fuzzy logic application . Multi geohazards macro-zone maps . Rahdar . Khuzestan, Iran
Introduction Geohazards are naturally occurring hazards on the Earth’s surface that place both natural and man-made objects in danger. Some of the most severe hazards include landslides, rock-
falls, hillside collapses, erosion and water washing in various facets, asymmetric subsidences, sinkholes, creep, liquefactions and large-scale ground failures. There are also some hazards that stem from a combination of land and atmospheric effects, such as floods and avalanches. (It should be noted that from the viewpoint of ground acceleration in bedrock, the role of earthquakes was studied separately but is still taken into the account when compiling the above-mentioned maps.) These hazards can cause destruction to farm fields and hillsides, as well as man-made features such as buildings, roads, canals, water mains and networks, and the electricity distribution network. Severe instances can cause causalities as well. Therefore, specifying each phenomenon and creating maps of their locations is an effective strategy toward sustainable development of the affected lands. Creating a multi geohazards macro-zone map that includes all possible geohazard phenomena is imperative as well. Multi geohazards macro-zone maps must take into account all hazards in nature. Because of the variety of hazards, it is unwieldy to show macro-zones for all of the individual geohazard phenomena in a single map. Also, absolute quantification
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