Understanding flood regime changes in Europe: a state of the art assessment

Abstract

Abstract. There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has been obtained through two approaches. The first approach is the detection of change based on observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for non-linear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities are discussed again such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on flood-rich and flood-poor periods rather than on flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.

Hydroclimatology of extreme river flows

“…Indices are valuable for detecting trends and other changes in regional and global river flow (Cloke & Hannah, 2011;Gudmundsson et al, 2012;. However, our knowledge of extreme flow characteristics is influenced substantially by the spatial and temporal extent of observational records (Hannaford et al, 2013;Hall et al, 2014). Furthermore, universal definitions and quantifications of flow events are usually inappropriate Folland et al, 2015) for three principal reasons.…”

“…At the global scale, energy inputs to Earth's surface (Ramanathan, 1981;Wild, Ohmura & Cubasch, 1997;Andrews, Forster & Gregory, 2009) and the intensity of wet and dry periods (Giorgi et al, 2011) are anticipated to increase, although with pronounced regional variability (Solomon et al, 2007;Prudhomme et al, 2014). Furthermore, a changing climate may drive land use changes and human responses to reduced water security that may further affect hydrological regimes (Hall et al, 2014). Consequently, the characteristics of climatic variability and hydrological responses should be anticipated to change (Watts et al, 2015) and may exceed the bounds of present variation.…”

New Estimates of Variations in Water Flux and Storage over Europe Based on Regional (Re)Analyses and Multisensor Observations

“…For these regions, changes in P usually implicate an increase of extreme precipitation events (Coumou and Rahmstorf 2012) leading to more frequent and severe flooding (Hall et al 2013). On the other hand, observed positive trends in E have been attributed to rising temperatures and radiation and are found to be constrained by moisture supply (Jung et al 2010).…”

The influence of hydroclimatic variability on flood frequency in the Lower Rhine

“…The size and physiography of the Rhine catchment is also of importance, as the northern part and southern parts of the catchment demonstrate rather opposite modes of flood activity, in line with the larger climatic zonation in Western Europe in response to Atlantic storm track configuration and temporal changes therein (e.g. Marshall et al, 2001;Magny et al, 2003;Mudelsee et al, 2004;Dankers and Feyen, 2009;Foulds et al, 2014;Hall et al, 2014;Schulte et al, 2015). The trunk valley of the Rhine crosses these zones in a north-westward direction, building up a cumulative flooding regime from subcatchments with mixed responses to changes in storm track configuration and general climate change.…”