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 characterise management shortcomings, hazard, exposure, vulnerability and impacts of all events; 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 socio-hydrological models. The dataset is available to the public through the GFZ Data Services (Kreibich et al. 2023, link for review: https://dataservices.gfz-potsdam.de/panmetaworks/review/923c14519deb04f83815ce108b48dd2581d57b90ce069bec9c948361028b8c85/).</p

An analysis of the hydrological regime as a factor influencing on the distributions of maximum annual flows

Statistical models of freshet flows are the basis for the design of hydrotechnical structures and for undertaking all and any activities related with flood threat. With regard to the method of data preparation for estimation and to the estimation procedure itself, the methods applied in such situations can be divided into two parts - FFA (Flood Frequency Analysis) and POT (Peak Over Threshold). In this study a comparison of those methods is made, using an original mixture of distributions (FFA) and an original procedure of distribution estimation (POT) for six selected water gauges on the river Odra

Estimation of parametric flood hydrograph determined by means of Strupczewski method in the Vistula and Odra catchments

While determining theoretical flood hydrographs, different methods of their construction are used depending on the needs of the problem or the scope of the project. It should be remembered that these methods differ mainly with the principle of the waveform averaging, which may be done either according to the flow or time. The hydrographs may be divided into nonparametric (determining on the basis of registered floods) and parametric (using mathematical description of the flood course). One of the analytical methods is Strupczewski method which has two parameters: responsible for the waveform and specifies the base flow, the flow above which values of hydrograph are calculated. The functional description uses the Pearson type III density distribution

An analysis of the hydrological regime as a factor influencing on the distributions of maximum annual flows

Statistical models of freshet flows are the basis for the design of hydrotechnical structures and for undertaking all and any activities related with flood threat. With regard to the method of data preparation for estimation and to the estimation procedure itself, the methods applied in such situations can be divided into two parts - FFA (Flood Frequency Analysis) and POT (Peak Over Threshold). In this study a comparison of those methods is made, using an original mixture of distributions (FFA) and an original procedure of distribution estimation (POT) for six selected water gauges on the river Odra

Urban drought

Drought is recognized as one of the most complex natural hazards that have a large negative impact on society, economic sectors and the environment. Drought events affect freshwater resources and can become a great threat to urban water supply systems. According to climate change projections with an increase of air temperature and duration of dry periods, cities may experience a serious water shortage in the future that can limit sustainable urban development. Water-related consequences in urban areas can concern various socio-economic sectors as well as urban ecosystems. This paper focuses on drought in urban areas as an event of below-average natural water availability that can result in difficulties in meeting the water needs of socio-economic sectors and ecosystems particularly vulnerable to drought. Drought vulnerable sectors were identified within the local context of the City of Wroclaw area. Long-term analyses of meteorological and hydrological indicators were performed in order to estimate the drought hazard in Wrocław. A combination of water shortage hazard and the vulnerability of water users were the basis to assess local drought risks. Reducing the drought risk requires coherent actions from both city and water managers. The paper presents a set of recommendable measures to avoid potential water shortages and to cope with impacts of drought in the Wroclaw area

Urban drought

Drought is recognized as one of the most complex natural hazards that have a large negative impact on society, economic sectors and the environment. Drought events affect freshwater resources and can become a great threat to urban water supply systems. According to climate change projections with an increase of air temperature and duration of dry periods, cities may experience a serious water shortage in the future that can limit sustainable urban development. Water-related consequences in urban areas can concern various socio-economic sectors as well as urban ecosystems. This paper focuses on drought in urban areas as an event of below-average natural water availability that can result in difficulties in meeting the water needs of socio-economic sectors and ecosystems particularly vulnerable to drought. Drought vulnerable sectors were identified within the local context of the City of Wroclaw area. Long-term analyses of meteorological and hydrological indicators were performed in order to estimate the drought hazard in Wrocław. A combination of water shortage hazard and the vulnerability of water users were the basis to assess local drought risks. Reducing the drought risk requires coherent actions from both city and water managers. The paper presents a set of recommendable measures to avoid potential water shortages and to cope with impacts of drought in the Wroclaw area

A Novel Method of Design Flood Hydrographs Estimation for Flood Hazard Mapping

Flood hazard mapping requires knowledge of peak flow as well as flood wave volume and shape, usually represented as a design flood hydrograph (DFH). Statistical approaches for DFH development include nonparametric and parametric methods. The former are developed from long-term flow observations and are thus related to the physio-hydro-climatological catchment properties, but not applicable for ungauged catchments. The alternative parametric DFH can be estimated for any river cross-section, but its links with catchment characteristics are limited. The goal of this study was to introduce a novel hybrid approach for DFH estimation, where the parametric DFH is estimated from the selected properties of the nonparametric DFH (hydrograph width at the levels of 50% and 75% of the peak flow and skewness coefficient) that can be related to the catchment characteristics. The model that offers effective parameter estimation and best correspondence to the reference observation-based hydrograph was selected from among Gamma distribution, Strupczewski and Baptista candidates. The method was validated for 34 catchments of the upper Vistula River and Middle Odra water regions (Poland) based on data from the 1964&ndash;2010 period. The Baptista method was found to provide the best model for hybrid DFH construction according to the applied quality measures

Flow descriptors for parametric hydrographs accounting for afforestation of the catchment

Parametric flow hydrographs are used for design and management purposes in such fields as water management and aquatic engineering. They describe a theoretical hydrograph based on such parameters as maximum flow, time to peak, and surge duration. They are used to forecast flood risk and to evaluate the impact of land use on the run-off hydrograph. In Western Europe for many years methods have been used in which parametric hydrographs are determined based on physical catchment descriptors (PCDs), which are divided into three groups describing the physical features of a catchment. These descriptors are used to derive formulae enabling the determination of parametric flow hydrographs for any computational crosssection. In this work, such formulae are derived for the catchment of the Raba River, using the principles of design hydrology applied in Western European countries. The parametric hydrograph is described using Baptista’s gamma density function. The input hydrograph was a nonparametric flow hydrograph determined by Archer’s method. For nine gauging stations located in the Raba catchment, physical catchment descriptors were obtained for two 30-year periods: 1961-1990 and 1983-2012. Based on the nonparametric flow hydrograph and the PCDs, two groups of formulae were derived to describe the parametric hydrograph. Analysis of agreement between the computed parametric flow hydrographs and the input hydrograph indicated a high quality of fit. It should be noted that the formulae and analysis presented here refer only to the Raba catchment. However, the results confirm the possibility of applying these methods to the determination of parametric flow hydrographs for any river cross-section

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

The challenge of unprecedented floods and droughts in risk management

International audienceAbstract Risk management has reduced vulnerability to floods and droughts globally 1,2 , yet their impacts are still increasing 3 . An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data 4,5 . 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 change 3