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

An attemt to estimate the precipitation value causing summer floods in the middle Odra basin

Oszacowanie wysokości opadów wywołujących letnie wezbrania w dorzeczu środkowej Odry wykonano na podstawie dobowych sum opadów z 53 stacji opadowych w wieloleciu 1971-2005. Krytyczną wartość opadu poszukiwano spośród wartości 5-dniowych sum opadów o prawdopodobieństwie przewyższenia (p) od 10% do 0,1%. Wyznaczono zależności funkcyjne pomiędzy prawdopodobieństwem przewyższenia danej sumy opadu a wysokością nad poziomem morza. Uzyskane zależności pozwoliły na ocenę częstości przewyższeń danej sumy opadów w określonym piętrze wysokościowym. W poszczególnych latach badanego wielolecia wyznaczono ilość 5-dniowych epizodów opadowych w poszczególnych przedziałach p: >10%, [10% –5%), [5% – 2%), [2% – 1%), [1% – 0,1%), ≤ 0,1%. Uporządkowując uzyskane zestawienie według ilości epizodów o prawdopodobieństwie p ≤ 1%, wyselekcjonowano lata, w których wystąpiły znaczne obszarowo wezbrania w dorzeczu środkowej Odry. Z analizy zależności pomiędzy średnią wartością opadu a stopniem zagrożenia obszaru oszacowano wysokości opadu, które mogą powodować średnie i poważne zagrożenia wezbraniowe.Evaluation of the precipitation value causing summer floods in the Middle Odra basin was done on the basis of daily precipitation totals within the period of 1971–2005 recorded at 53 precipitation stations. The critical value of precipitation was searched among the values of 5-days precipitation totals with the probability of exceeedance (p) of 10% and lower. The functional relationships between precipitation values of the given p and the altitude of the stations were identified. They were used to estimate the range of precipitation values of given p for the altitude layers. For each year a number of 5-days precipitation totals of the following p: >10%, [10% – 5%), [5% – 2%), [2% – 1%), [1% – 0,1%), ≤ 0,1% was calculated. Arranging the obtained results by the number of events of p≤1% let to designate the years of the severe and extended floods in the middle Odra basin. While analyzing the relationship between mean areal value of precipitation and the number of critical precipitation incidences, the values of precipitation causing moderate and severe risk of summer flood were estimated

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