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1. Introduction
Flooding is the most common natural hazard distressing people worldwide. It has been estimated that about a third of the total landscape of the earth is flood-prone, consequently affecting approximately 82 per cent of the world’s population (Dilley et al., 2005). World Meteorological Organization (World Meteorological Organization (WHO), 2014) asserted that between 1970 and 2012, about 89 per cent of the reported global disasters were due to flooding and storms, resulting in deaths of millions and huge economic losses. Globally, economic losses from flooding exceeded $19bn in 2012 (Visser et al., 2012; IPCC, 2012; Ward et al., 2013). The twentieth century witnessed an unprecedented rate of flood occurrences within the most drainage basins of the world (Perry, 2000). The yearly evaluation shows that in the past 50 years (1945 to 2005), flood incidence has increased by almost 10-fold (Scheuren et al., 2008). The statistics inarguably suggests that flooding is a global environmental issue that requires consistent monitoring and mitigation.
Structural measures may significant reduce the losses associated with floods; however, they cannot completely eliminate the flood risk (Bailey et al., 1989; Alexander and Wilson, 1995; Watson and Biedenharn, 2000; UNISDR, 2011; FEMA, 2012). There are other aspects such as hazard intensity, spatial exposure, social structure and demographic composition that need to be taken into account in the process of flood risk reduction. Therefore, an integrated assessment method, including maximum possible parameters is needed to address residual risk. Considering the multi-faceted nature of risk, UNISDR defines risk assessment as “a qualitative or quantitative approach to determine the nature and extent of disaster risk by analysing potential hazards and evaluating existing conditions of exposure and vulnerability that together could harm people, property, services, livelihoods and the environment on which they depend”. Thus, to minimise both human suffering and the economic loss, the risk is be assessed in a comprehensive manner considering hazard, spatial exposure and vulnerability (Turner et al., 2003; Adger et al., 2004; Flanagan et al., 2011). Moreover, the use of a geographic scale sufficient to depict spatial differences in risk is also important (Flanagan et al., 2011). The scale implications need more attention and documentation in risk studies (Fekete et al., 2009). Portraying...