Panta Rhei benchmark dataset: socio-hydrological data of paired events of floods and droughts

As the adverse impacts of hydrological extremes increase in many regions of the world, a better understanding of the drivers of changes in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is currently a lack of comprehensive, empirical data about the processes, interactions, and feedbacks in complex human–water systems leading to flood and drought impacts. Here we present a benchmark dataset containing socio-hydrological data of paired events, i.e. two floods or two droughts that occurred in the same area. The 45 paired events occurred in 42 different study areas and cover a wide range of socio-economic and hydro-climatic conditions. The dataset is unique in covering both floods and droughts, in the number of cases assessed and in the quantity of socio-hydrological data. The benchmark dataset comprises (1) detailed review-style reports about the events and key processes between the two events of a pair; (2) the key data table containing variables that assess the indicators which characterize management shortcomings, hazard, exposure, vulnerability, and impacts of all events; and (3) a table of the indicators of change that indicate the differences between the first and second event of a pair. The advantages of the dataset are that it enables comparative analyses across all the paired events based on the indicators of change and allows for detailed context- and location-specific assessments based on the extensive data and reports of the individual study areas. The dataset can be used by the scientific community for exploratory data analyses, e.g. focused on causal links between risk management; changes in hazard, exposure and vulnerability; and flood or drought impacts. The data can also be used for the development, calibration, and validation of sociohydrological models. The dataset is available to the public through the GFZ Data Services (Kreibich et al., 2023, https://doi.org/10.5880/GFZ.4.4.2023.001)

The challenge of unprecedented floods and droughts in risk management

Risk management has reduced vulnerability to floods and droughts globally1,2, yet their impacts are still increasing3. An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data4,5. On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change3

Systèmes d'analyses météorologiques dans le Nord-Est de l'Espagne : Validation de SAFRAN et SPAN

International audienceWe present an application and validation of the SAFRAN meteorological analysis system for north-east Spain. SAFRAN is also compared to the SPAN analysis system and the meteorological model HIRLAM-HNR, both operational at AEMET. This application of SAFRAN is intended for hydrological studies. This is the first study that shows an application of SAFRAN outside of France and that compares it with SPAN. This is also the first article validating SPAN's rainfall values. Using one year of observational data, the results show that both SAFRAN and SPAN have a similar performance, which is also similar to SAFRAN's performance in France. Thus, SAFRAN and SPAN are both good tools to force land surface models at high resolution in the area of SAFRAN works under the assumption of the existence of climatically homogeneous zones. Two different sets of zones were tested, one based on the AEMET meteorological warning zones and another one based on hydrological catchments. Better results were obtained when using meteorological warning zones. However, the difference is small. In north-east Spain, SAFRAN has the same limitations that were previously shown in France: the spatial structure of the fields is not realistic enough and wind speed is underestimated. As expected, both SAFRAN and SPAN work better in flat areas than over areas of steep relief. This can be a problem in hydrological studies, especially for the Ebro river basin, where most of the runoff is generated in the Pyrenees

Projet Cyprim, partie II : Impact du changement climatique sur les événements de pluie intense du bassin méditerranéen

Un deuxième thème abordé dans le cadre du projet Cyprim vise à caractériser, dans le contexte du changement climatique, l'évolution des phénomènes de pluie intense en région méditerranéenne. À cette fin, une simulation climatique de 1960 à 2099 a été réalisée à l'aide d'un modèle régional couplé océan-atmosphère sous le scénario d'émissions A2 du Giec. Différentes méthodes de descente d'échelle (jusqu'à une échelle très fine de 2km) et de détection d'environnements synoptiques favorables aux précipitation sintenses sont ensuite proposées pour estimer l'impact du changement climatique sur les précipitations et l'hydrologie du sud-est de la France, tant du point de vue saisonnier que lors des épisodes de pluies intenses.A second topic covered by the CYPRIM project(1) aims to characterize the evolution of heavy precipitation events in Mediterranean in the context of climate change. To this end, a continuous climate simulation from 1960 to 2099 has been run using a regional ocean-atmosphere coupled model under IPCC A2 emission scenario. Various techniques of downscaling, down to the very fine 2 km scale, and methods to highlight synoptic environments favourable to heavy rain, have been used to estimate the impact of climate change on precipitation and hydrology over South-East France, both for the whole autumn season and the heavy rain events

Temperature-precipitation extremes relationship in the Mediterranean: past climate assessment and projection in anthropogenic scenarios

International audienc