Managing hydro-meteorological risks is a multi-disciplinary task, requiring understanding of the various processes that eventually determine the impact.  
Hans de Moel, Institute for Environmental Studies, VU University, Amsterdam

Novel concepts for improved impact and risk assessments

Hydro-meteorological risks such as floods and droughts can have huge repercussions on the well-being of human society, both in terms of human suffering and economic impact.

Risk assessments form the basis for decision-making in the management of hydro-meteorological risks. With risk management approaches becoming more prevalent, there is a clear need for improved knowledge and methods to assess the risks.

IMPREX further developed four promising novel concepts related to hydro-meteorological risk assessment. In addition to methodological developments, the concepts were tested in case study areas with stakeholders in order to gain experience on their practical applicability and to illustrate their usefulness for decision-making.


Listen to Hans de Moel, IMPREX Project Partner from the Institute of Environmental Studies (Free University of Amsterdam), explain the novel concepts from the IMPREX study tackling hydro-meteorological risks.


Novel concept 1: Climate variability and flood/drought risks

Our capability to prepare for disasters is challenged by large uncertainties and our limited understanding of important driving forces of hydro-meteorological hazards, such as climate variability.

Large-scale indices of climate variability (e.g. El Niño Southern Oscillation or the North Atlantic Oscillation) are often used for seasonal forecast models to predict upcoming weather conditions in monthly to seasonal scale.

However, little knowledge exists about the relationships between these large-scale indices and their impacts on society, such as flood damages and crop productivity. Combining improved weather variability predictions with empirical models on potential impacts creates opportunities for the management of hydro-meteorological risks.

IMPREX explored the direct relationships between natural climate variability and flood and drought impacts, allowing for fast and practical impact assessments on the basis of known climatic oscillations.

The developments can feed into risk outlooks and early warning systems in areas that are prone to floods and droughts for a variety of sectors (i.e. agriculture, hydropower, emergency aid, etc.). The seasonal predictions can enable better disaster prevention, mitigation and preparedness by stakeholders and can improve the climate resilience and sustainability of these sectors.

You can find more information in our report on new methods to enhance seasonal prediction.

Crop yields and flood impacts derived from large scale climate indices

Probabilities of occurrence of high-impact extremes are linked to governing large scale climatic patterns. Advanced machine learning techniques have been used to relate a number of influential climate patterns to the occurrence of both, floods and crop yield anomalies in different European subdomains. The techniques are designed to extract information from past observations that could be used to make a forecast of the probability of major future impacts encompassing a time range of a few months. Also, prediction of anomalies in sugar beet production can be made, for some regions, up to six months before the start of harvesting season. This work was carried out in partnership with the European Joint Research Centre. Some of these results are used in the IMPREX risk outlook displaying an assessment of risks for hydrological impacts at a lead time of a couple of months, derived from multiple lines of evidence. In a follow-up study carried out by IVM, the method was extended by including bottom-up local knowledge, which implies an active use of stakeholder information and people’s perceptions of risk.

The work shifts the focus from forecasting hazards towards impacts, which is a promising approach to generate meaningful outlooks and early warnings for targeted stakeholders.

You can find more information in our report on index-based drought risk assessment.

Climate variability and flood/drought risks
Climate variability and flood/drought risks

Novel concept 2: Future weather and compound events

Conventionally, to assess climate risks, univariate climate statistics (e.g. return periods of precipitation or water levels) are derived from either historical observations or (downscaled) climate model simulations. However, this approach does not give insight into future changes in the joint occurrence of two or more events (e.g. extreme precipitation and a storm surge at the same time), also known as compound events.

A realistic simulation of compound events requires the use of high resolution weather models, as opposed to coarser climate models, to have the right (spatial and temporal) resolution and processes relevant for extreme weather events. This can be run under the climate conditions of interest (such as a future climate) and coupled to impact models (hydrologic and/or hydraulic).

This new concept, called Future Weather (FW), has been developed to complement the traditional approach in climate impact research. The concept adds to the physical understanding of drivers of high impact hydro-meteorological events by using numerical weather prediction models to project high impact weather events in a future climate.

Moreover, Future Weather provides information to stakeholders at the local scale where climate change is experienced as changes in high-impact weather. The concept may also aid in increasing awareness of climate change and its impacts by visualising future weather cases and relating these to present day experiences.

Within IMPREX, FW was applied in case studies in the Netherlands and the UK. Risks to compound flooding were analysed in the current and future climate in consultation with the stakeholders. 

Inclusion of compound events in risk analysis

The need to consider compound events has been documented in an IMPREX policy brief for European Flood Risk management and flagged by authoritative publications by IPCC. With help from IMPREX a new European COST action DAMOCLES has been launched to promote awareness and systematic analysis.

In IMPREX, work has been carried out including the development of new model data sets and analysis concepts, targeted at studying its relevance for flood risk management in a number of smaller Dutch catchment areas and municipalities. The notion of compound events is well appreciated by many stakeholders involved in IMPREX and is a component of the commercial portfolio of consultancy firms like HKV.

In order to be absorbed in the stakeholders’ decision processes, the advantages of this method need to be clear and convincing. Pilot studies conducted within IMPREX contribute to the identification and demonstration of these advantages. Usage of this method in day-to-day work of companies like HKV will further increase the awareness of this method among stakeholders.

Future weather and compound events
Future weather and compound events

Novel concept 3: Methods to support drought risk management

Drought is one of the major natural hazards frequently causing large impacts worldwide. To prepare for future droughts, proactive drought management – a systematic process to prevent, mitigate and cope with drought-induced disaster management – is promoted over reactive emergency management.

While becoming well embedded in flood management, the application of risk management in drought and water resources management is much more complex because of the many users and sectors involved and the different ways in which a shortage of water can cause damage.

Within IMPREX, a conceptual framework for the quantification of drought-related risks, taking into account both the probability of drought-related hazards and their possible impacts, was further developed. In moving this framework forward, IMPREX considered a variety of end-users/sectors and made a step towards a decision-support tool. The framework was developed in cooperation with end-users in concrete case studies in the Rhine-Meuse delta region.

Based on this concept, tools can be designed to support quantitative risk-informed decision-making for fresh water management in the Netherlands. Within the IMPREX project, such methods and tools provided decision-making support to the Dutch Delta Programme on water supply levels.

Methods to support drought risk management
Methods to support drought risk management

Improvements to the drought risk management toolkit AQUATOOL

Within IMPREX, tools, models and approaches are improved that support decision making for both operational drought management, water allocation, and long-term risk planning. Over the past decades a sophisticated Decision Support System has been developed, and the components dedicated to the data processing and quantitative modelling are embedded in a series of modules in the AQUATOOL decision support system.

In IMPREX various incremental improvements have been implemented in some of these modules:

  • an evaluation of the seasonal predictability of droughts in precipitation and streamflow forecasts has been carried out in the hydrological risk module of AQUATOOL
  • the seasonal forecasts are incorporated in the hydrological risk assessment module of AQUATOOL (SIMRISK).

The performance of this forecast product shows that bias corrections need to be applied, but small improvements are achieved in predicting the onset of the dry season compared to the operational procedure that is based on statistical modelling using observed precipitation records.

The developments of AQUATOOL are rooted in a long history of decision support system development for the Júcar area. However, the system can be implemented in any other basin abroad where the model chain and AQUATOOL calibrated modules are available.

By the main stakeholders this work is perceived as a first step towards inclusion of seasonal forecasting in the drought management support system. The tailor-made delivery of the probabilistic information for the target region, the Júcar basin, was well understood and appreciated.

AQUATOOL has strongly contributed to the refinement and greater acceptance among local stakeholders although more research is needed in order to further improve the predictions.

You can find more information in our report on the application of multihazard risk management tools.

Novel concept 4: Probabilistic impact assessment

The basis for efficient risk management is a comprehensive and reliable risk assessment. Risk assessments extend the hazard analysis with an analysis of potential impacts (i.e. damage to buildings/crops) and as such investigate exposure and vulnerability/susceptibility of elements at risk, like companies or residential buildings.

Currently, assessments of potential impacts in the framework of hydro-meteorological risk analyses have in common that complex damaging processes are described by relatively simple, deterministic approaches, which are associated with high uncertainty.

Probabilistic (as opposed to deterministic), multi-variable flood damage models have the potential to significantly improve the description of damaging processes and inherently provide uncertainty information. Within IMPREX, the research agenda focused on further developing these models to enable their applicability in medium- and large-scale flood risk analyses.

Decreasing the uncertainty present in stakeholders’ risk analyses with quantitative information and improved impact assessments can lead to better risk management decisions, for instance related to cost-benefit evaluations and management of insurance portfolios (i.e. setting premiums and covering by re-insurance).

Probabilistic impact assessment
Probabilistic impact assessment


Mapping impacts of remote climate extremes on food and manufacturing chains

In the globalising world, trade shocks induced by floods in production areas depend strongly on the trade network. Increased trade connectivity allows faster propagation of shocks through the trade network, but also allows effective mitigation by choosing alternative supply channels. In general, a strong connectivity in combination with a balanced trade relation limits propagation of adverse flood effects to partner regions and improves mitigation options.

An extensive analysis was made for water consumption and trade networks in the crop production industry. Linking the trade and production chains with ambient climate features allowed us to produce a climate risk profile for each of these crops. To map and analyse the impacts of flood-related shocks in the system, we used a trade network model – Acclimate.

The mapping uses a discretisation into regions and sectors and is assumed to cover a majority of the total worldwide economic production. The system is driven by national or regional economic statistics and allows mapping global trade balances between regions and the effects of cascading effects of climatic shocks on those trade balances.

These analyses can inform international food production or retail companies about the current and potential future vulnerability of their supply chains. This enables the development of coping strategies to reduce risk risks (i.e. through targeted portfolio diversification) or forecast-based action in the face of impeding disasters.

You can find more information in our report on dependence of Europe’s economy on other parts of the world in terms of water resources.

Risk Outlook Tool

Do you need to plan for upcoming water-related risks, such as floods and droughts?

Within the IMPREX project, we developed a tool that teaches you about season-ahead predictions of hydrological risks whatever your level of hydrology expertise. Learn more while:


For more information about the four novel concepts, please see the project deliverables: