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Risk estimation of the drought on the island of Crete using multi-criteria analysis at a GIS environment

Anyfanti Ioanna

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Year 2016
Type of Item Diploma Work
Bibliographic Citation Ιωάννα Ανυφαντή, "Εκτίμηση επικινδυνότητας ξηρασίας στο Υ.Δ. Κρήτης με τη χρήση πολυκριτηριακής ανάλυσης σε περιβάλλον GIS", Διπλωματική Εργασία, Σχολή Μηχανικών Περιβάλλοντος, Πολυτεχνείο Κρήτης, Χανιά, Ελλάς, 2016
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The present thesis aims to assess the risk of drought in the aqueous compartment of Crete, using multi-criteria analysis in Geographic Information Systems (G.I.S) environment. More specifically, the factors that may affect water supplies and contribute to water scarcity were identified, and then were divided into two categories, after having been spatially modeled into maps. The first category is that of the dynamic factors and includes: a) precipitation and b) evapotranspiration by natural and cultivated vegetation. The second one is that of the stable factors and includes: a) available water capacity of the soil, b) surface flow accumulation, c) irrigation networks, d) groundwater level, e) hydrogeology of the area (depth to rock) and f) water intrusion in the coastal zones of Crete. Fuzzy sets is the mathematical background on which this thesis is based. At first place, the occurrence of drought is assigned with the value 1, while the opposite phenomenon (non- occurrence) is assigned with the value 0. Then, with the use of the appropriate fuzzifiacation functions, the numerical values of each factor are assigned with a degree of membership to the drought phenomenon. Through the use of the proper overlay functions, the fuzzified values of the factors of each category are combined and after that, the two different categories are combined as well, in order to determine each region’s degree of membership to drought.The data that were processed in order to depict the dynamic factors are derived from the measurements of two different time periods: a) from 1977 until 1997 and b) from 2010 until 2015, so that to observe the behavior of these factors in correlation with the stable ones. The final map is the mean average of the above periods and its regions are classified as of very low, low, medium, high and very high risk of drought occurrence.

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