Projections of Changes in Flood Hazard in Two Headwater Catchments of the Vistula in the Context of European-Scale Studi
European-scale flood hazard projections do not give a consistent view of future changes in Central Europe, including Poland. Some studies indicate decreases in the magnitude and frequency of high flows, whilst others show increases. In this chapter, we su
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RCP4.5 scenario. The results for both catchments are consistent with some of the previous European-scale studies, but do not give a coherent image. At this stage, the only explanation of the differences in the projections of future flood changes in both catchments lies in climatic variability and the uncertainty of the results. The results of this study confirm the view that flood hazard assessment is influenced by multiple climatic and non-climatic factors which introduce uncertainties and whose relative importance is site-specific. Keywords Flood hazard
Projections Uncertainty River Vistula Poland
1 Introduction Economic damage caused by river floods has grown considerably in recent decades, at all spatial scales, from local to global. Many river floods with material damage of the order of billions of euros and with multiple fatalities have been recorded in Europe. Since recent floods have reached new heights of stage and discharge records, there is a concern that not only flood damage may have increased, but also flood hazard (Kundzewicz et al. 2016). Increase of heavy precipitation has been noted in many areas as well but its effect on floods has been difficult to pinpoint. Also studies of change detection in observed high river flows show no convincing and ubiquitous increase of flood hazard, in Europe and world-wide (Kundzewicz 2012; Kundzewicz et al. 2005; Madsen et al. 2014). Nevertheless, some indications of an increasing tendency in the number of large floods in Europe, of considerable magnitude and severity, have been detected recently (Kundzewicz et al. 2013). It is important to stress that reliable determination of flood frequency characteristics requires long-term observations and continuous gauge records. Typically, however, existing time series of records are not long enough, or stations have been re-located over time, which renders analysis and interpretation difficult. In addition, flood trends cannot be easily detected in the observation record because the signal-to-noise ratio is typically low whereas natural variability is high. The failure to detect a ubiquitous rising trend in floods has apparently been a surprise to some experts describing recent flood events as possible harbingers of a rise in flood risk related to climate change. This was exemplified by the sarcastic title chosen by Schiermeier (2003): “Analysis pours cold water on flood theory”, when referring to failure to detect an increasing trend in a study reported by Mudelsee et al. (2003). Model-based large-scale projections of changes in river flood frequency indicate increases in the amplitude and frequency of high river flows in most areas of the world (but not necessarily in Europe) in the warming climate (Hirabayashi et al. 2008, 2013; Arnell and Gosling 2016; Dankers et al. 2014). In addition, and in the case of Europe in particular, considerable disagreement has been reported between projections (Lehner et al. 2006; Dankers and Feyen 2009; Rojas et al. 2011, 2012, Alfieri et al. 2015; Roud
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