Environ Earth Sci (2016) 75:319 DOI 10.1007/s12665-015-5157-1 ORIGINAL ARTICLE Urban flood hazard assessment in the basin of Athens Metropolitan city, Greece 1 2 1 1 G. D. Bathrellos • E. Karymbalis • H. D. Skilodimou • K. Gaki-Papanastassiou • E. A. Baltas3 Received: 1 July 2015 / Accepted: 13 October 2015 / Published online: 11 February 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract Flood events have often occurred in the A sensitivity analysis was made to assess the effect of the metropolitan urban area of Athens, capital of Greece, various factors on the flood hazard map. Three scenarios causing loss of property and in many cases human lives. In were developed to examine the effect of uncertainty of the this study a flood hazard assessment model for urban areas factors’ values to the flood hazard assessment results, is examined. The Kifisos and Ilisos Rivers flowing through leading to the corresponding urban flood hazard assessment the plain of Athens was the case study of the present work. maps. The produced map showed that the areas of very The quantitative analysis of the Kifisos and Ilisos Rivers high flood hazard are located mostly along the lower drainage networks was performed to identify flash-flood reaches of Kifisos and Ilisos Rivers, particularly to the prone areas. The major factors affecting urban floods were southern and to the western part of the study area. These estimated. The slope angle, elevation, distance from open areas are characterized by lowland morphology, gentle channel streams, distance from totally covered streams, slope, totally covered streams, expansion of impermeable hydro-lithology and land cover of the study area were used. formation and intense urbanization. The uncertainty anal- to evaluate these factors the analytical hierarchical process ysis shows no significant differences on the spatial distri- method was applied in a geographical information system. bution of the hazard zones. The produced urban flood hazard map proves a satisfactory agreement between the flood hazard zones and the spatial distribution of flood & G. D. Bathrellos phenomena that have affected the study area in the past [email protected] 117 years. Furthermore, the comparison between the flood- E. Karymbalis prone areas that were derived from the geomorphological [email protected] analysis of the drainage networks and the high flood-hazard H. D. Skilodimou zones of the final map indicated reliable results and a high [email protected] accuracy of the proposed methodology. K. Gaki-Papanastassiou [email protected] Keywords Multi-criteria analysis Á Uncertainty analysis Á E. A. Baltas GIS Kifisos and Ilisos Rivers Morphometry [email protected] Á Á 1 Department of Geography and Climatology, Faculty of Geology and Geoenvironment, National and Kapodistrian Introduction University of Athens, University Campus, Zografou, 15784 Athens, Greece 2 Floods are among the most dangerous natural hazards Department of Geography, Harokopio University of Athens, affecting the development of an area. Worldwide, flood 70, El. Venizelou Str., Kallithea, Athens, Greece events cause the largest amount of deaths and property 3 Department of Water Resources and Environmental damage (CEOS 2003). On the other hand, increasing Engineering, School of Civil Engineering, National Technical University of Athens, Heroon Polytechniou 9, Zografou, urbanization and population have brought significant 15780 Athens, Greece effects on the natural environment. In urban areas, human 123 319 Page 2 of 14 Environ Earth Sci (2016) 75:319 activities such as uncontrolled building construction, land- uncertainty associated with spatial outputs (Benke et al. use changes and lack of urban planning affect flooding. 2009). More than 40 % of the national population lives in the The Kifisos and Ilisos Rivers flowing through the plain metropolitan urban area of Athens, capital of Greece. The of Athens were the case study of the present work. Mor- plain of Athens has been extremely urbanized during the phometric parameters of the drainage network were used to last 70 years and the environment has changed dramati- examine its structural irregularities, as well as to identify cally. Dense, uncontrolled building constructions at loca- areas prone to flash floods and compare them with the tions blocking the axis of drainage network have caused results of the proposed model. several flood events (Karymbalis et al. 2012; Skilodimou The aim of this study is to present a flood hazard et al. 2003) resulting in the loss of property and in many assessment model for urban areas. Geomorphological and cases, human lives (Diakakis 2013; Diakakis et al. 2012; geological factors along with land use data were used for Maroukian et al. 2005; Mimikou et al. 2002; Mimikou and that purpose. The AHP is implemented to support the Koutsoyiannis 1995). Therefore, flood management con- evaluation of these factors, whereas the data processing and stitutes a very demanding condition for the protection of a the compilation of the urban flood-hazard map were per- human community. The geomorphologic characteristics of formed in a GIS environment. Furthermore, a sensitivity the basin’s drainage network influence the flood-hazard analysis of the factors was made to examine their varia- zones. Morphomertic analysis is used to determine the tions’ effect on the spatial and quantitative distribution of influence of drainage-network morphometry on flooding hazard areas. and to estimate the potential flood hazard in several works (Angillieri 2008; Mesa 2006; Migiros et al. 2011; Moussa 2003; Ozdemir and Bird 2009; Patton and Baker 1976; Study area Youssef et al. 2011a). The urban flood-hazard assessment is important for the The climate of the study area is typical Mediterranean. mitigation of floods and a necessary step for government According to the hydrometeorological data of the meteo- policies on urban planning worldwide. Urban flood-hazard rological station of Piraeus, the mean annual precipitation maps classify the various parts of land surface according to for a time-period of 30 years (1973–2003), is 332.2 mm. the degree of actual or potential flood hazard. They help the The rainy period begins in October and ends in May. The planners manage better the sites for urban development and mean annual air temperature reaches 18.8 °C, whereas the recognize areas that probably need stormwater runoff hottest month is August with a mean maximum tempera- infrastructure (Bu¨chele et al. 2006). The reliability of ture of 27.8 °C. January is the coldest month with a mean hazard maps depends mostly on the available data and the minimum temperature of 10.3 °C. applied methodology (Papadopoulou-Vrynioti et al. 2013a, The Kifisos River operates as the major drainage channel b). To this direction, geographical information systems for the largest part of the plain of Athens, which includes the (GIS) may help a lot with the spatial analysis of a flood, city of Athens and most of its suburbs (Fig. 1). The length of which is a multi-dimensional phenomenon. the main Kifisos channel is 33.7 km, and follows a NNE– Multi-criteria analysis methods are decision support SSW flow direction. It is a sixth-order stream flowing tools for the solution of complex decision problems. The through the urban area of Athens for approximately 25 km analytical hierarchical process (AHP) is a semi-quantitative and discharges into the Saronic Gulf. Its drainage basin has and multi-criteria methodology designed for hierarchical an area of 374.6 km2 and is surrounded by the mountains of representation of a decision-making problem (Saaty 1977, Parnitha (1413 m a.s.l.), Penteli (1109 m a.s.l.), Egaleo 2004). The AHP has gained wide application in land use (468 m a.s.l.) and Ymittos (1026 m a.s.l.). suitability (Bathrellos et al. 2012, 2013; Kamberis et al. Regarding the geological formations of the drainage 2012; Kokinou et al. 2015; Panagopoulos et al. 2012; basin, at the upper reaches of the Kifisos River alpine and Papadopoulou-Vrynioti et al. 2013a, b, 2014; Skilodimou post-alpine geological formations occur, with post-alpine et al. 2014; Thapa and Murayama 2008; Youssef et al. ones covering the 65 % of the total extent of the drainage 2011b), in landslide susceptibility analysis (Ayalew et al. area. The formations of the alpine basement belong to the 2004; Rozos et al. 2011; Youssef et al. 2015) and in flood geotectonic units of Attica and Ypopelagoniki and are hazard estimation (Ferna´ndez and Lutz 2010; Tehrany easily distinguishable near the adjacent mountains. The et al. 2014a, b). Moreover, the integration of the AHP in a Attica geotectonic unit consists of schists (Permian–Tri- GIS is able to improve decision-making methodology with assic age), marbles (Triassic–Jurassic), the Athens’ schists powerful visualization and mapping capabilities and of Cretaceous age and the Upper Cretaceous limestones of facilitates the production of hazard maps. However, the Athens. The geological formations of the Ypopelagoniki AHP method does not have the ability to identify the unit include clastic rocks (sandstones, schists and phyllites) 123 Environ Earth Sci (2016) 75:319 Page 3 of 14 319 Fig. 1 The location map of the study area with elevations, main channels of drainage network, building blogs and road network of Middle Triassic age, limestones (Triassic–Jurassic), suffered extensive damage during extreme storm events. ophiolites, Upper Cretaceous limestones and flysch (Lep- More than 25 severe flood events have happened during the sius 1893). An extensive area of the low-lying plain of last 117 years (Maroukian et al. 2005). Athens, as well as the slopes of the surrounding mountains A severe flood happened on February 22, 2013 where more are composed of post-alpine formations, which can be than 100 mm of rainfall was locally recorded in 5 h. The divided into Tertiary and Quaternary deposits of terrestrial heavy rain was the worst seen in the Greece’s capital for the and marine origin (conglomerates, marls, sandstones, last 50 years.