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 traditionally been obtained through two alternative research approaches. The first approach is the data-based detection of changes in 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 nonlinear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities associated with flood change scenarios are discussed 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 long duration records and flood-rich and flood-poor periods rather than on short duration 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.

Highlights

  • Europe has experienced a series of major floods in the past years: extreme floods in central Europe in August 2002 (e.g. Ulbrich et al, 2003) and in England in summer 2007 (e.g. Marsh, 2008), unprecedented flash flooding in western Italy in autumn 2011 (e.g. Amponsah et al, 2014), and more recently extreme floods in central Europe in June 2013 (e.g. Blöschl et al, 2013a)

  • Future flood discharges and their exceedance probabilities, together with changes in the time of flood occurrence within the year, are the key variables needed in order to be able to prepare future flood management strategies

  • The purpose of this paper is to review the current understanding of flood regime changes of European rivers – in particular, whether changes have been observed in the past, the drivers of change, what changes are likely to be expected in the future and what methods are currently used to detect and analyse flood changes

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Summary

A need for understanding flood regime changes

Europe has experienced a series of major floods in the past years: extreme floods in central Europe in August 2002 (e.g. Ulbrich et al, 2003) and in England in summer 2007 (e.g. Marsh, 2008), unprecedented flash flooding in western Italy in autumn 2011 (e.g. Amponsah et al, 2014), and more recently extreme floods in central Europe in June 2013 (e.g. Blöschl et al, 2013a). Blöschl et al, 2013a) As these and many other recent floods have exceeded past recorded levels, there is a growing concern that flooding in Europe has become more frequent and severe together with an increasing apprehension that human actions may play a key role in driving these flood changes. The public’s growing concern on anthropogenic influences and floods seems to be mainly caused by increasing flood damage and comprehensive media coverage of extreme events (Barredo, 2009). Hydrologists have been grappling with understanding and predicting floods since their science began They are exploring the question of whether floods are increasing and, if so, why. Changes in flood impacts such as vulnerability, exposure, perception or emergency management are not considered as the paper focuses on the changes in the river flood regime

Potential drivers of flood regime changes
Methods for understanding flood regime changes
Types of changes
Variables of changes
Methods of trend detection
Floods during the instrumental period
Historical floods
Flood change detection – challenges and opportunities
Observation biases and data opportunities
The Hurst phenomenon and nonlinearities
Methods of scenario analysis
Rivers: hydraulic structures and stream morphology
Catchments: land use and land cover
Atmosphere: climate
Flood change projections in Europe
Hydrological modelling uncertainty
Ensemble spread in climate variables
Feedbacks
A synthesis of approaches
Going beyond trend analysis of floods
Attributing causes to observed flood changes
Validating scenarios against observed flood regime dynamics
Low-dimensional change models for flood changes
Need for a European-wide effort
Building blocks of a European flood change research network
Findings
Recommendations
Full Text
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