The number of fatalities, as well as the economic damages, caused by floods is increasing globally. In recent years a number of major floods have occurred in Europe: for example, the catastrophic flooding across central Europe in 2002 and 2010, and the flash flooding affecting the UK in 2004 and 2007. These events have triggered the common perception that flood risk is increasing, and environmental change (e.g., land-use change, inappropriate river management, climate variability) has raised ever increasing concern. Defining reliable and robust flood-risk assessment strategies for emerging and developing countries is also a pressing need, since the lack of data is often associated with inappropriate land-uses and developments.

To assess and contrast these dramatic developments and impacts, a better understanding of flood processes is essential. This is not an easy task as human activities have disrupted the natural hydrological regimes so that, nowadays, most river basins cannot be considered pristine. The scientific literature clearly points to the importance of hydrological change detection and understanding, especially through improving process-understanding and separation of anthropogenic from natural variations, possibly avoiding overemphasis on trends. In this context, remote sensing data also have great potential value. The development of weather radar techniques for rainfall estimation and the growing use of satellite imagery for flood extent mapping are two encouraging examples.

The study of spatial and temporal patterns of floods has a long tradition in hydrology. Spatial patterns of flood processes exist at different scales, from small-scale patterns resulting from different runoff production mechanisms operating within a single catchment, to large-scale patterns, caused by the regional variability in hydrometeorology. The analysis of spatial patterns is central to any regional flood frequency analysis procedure, and embodies the first principle proposed by the "Committee on Techniques for Estimating Probabilities of Extreme Floods" of the US National Research Council in 1988 for hydro-meteorological modelling: "substitute time for space". The analysis of temporal patterns of floods is fundamental to the understanding and assessment of variations in flood frequency regime. There has been an increasing need to assess uncertainties when studying spatial and temporal patterns of floods and analysing their possible impact on flood management. Whilst the complexity of the notion of uncertainty and its estimation methods have arguably hindered practical application, the development of more mature guidance on methods could help facilitate this in the future.

© 2011 by DLWRM FCE STU in Bratislava. Realization Fusion IS, s.r.o.