From global to local: improving flood forecasting with Destination Earth

To better protect millions of people worldwide from floods, Deltares is developing warning systems. By adding the data from Destination Earth, a digital twin of the Earth, to these systems, the impact of a flood can be even better estimated. This helps governments to improve flood warning and response and enabling humanitarian organisations to effectively deploy their resources and capacity.

Humber estuarium in het Verenigd Koninkrijk

Hundreds of millions of people worldwide are at risk of flooding from the sea, from rivers and from rainfall. To make the world safer from flooding, Deltares develops knowledge that is applied in information and warning systems, among other things. We are engaging in research with partners about how to best forecast flooding by providing more than fifty countries with Flood Early Warning Systems (FEWS).

Destination Earth is an initiative of the European Union to create a digital model of earth, that will be used to monitor the effects of natural and human activity on our planet, anticipate extreme events and adapt policies to climate-related challenges.

Reasons

Through our research in actionable early warning systems, we focus on expanding the range of flood drivers considered, including storm surge, waves, pluvial, and fluvial processes, developing efficient flood models and rapid forecasting capabilities, and translating forecasting results into actionable early warning messages. This helps speeding up the process of setting up new systems, and making the warnings easier to understand, for the benefit of decision-makers and the general public.

Compound Flooding

Compound flooding happens when people face the threat of flooding from the sea, rivers and from rainfall at the same time. This type of flooding results in significant casualties and widespread damage annually, especially at densely populated low-lying areas such as urban deltas, low-lying and steep coastlines, and Small Island Developing States (SIDS).

Deltares has been investigating these regions to gain a deeper understanding of compound flood impacts, with the goal of mitigating compound flood risk. As population growth, economic development, and climate change accelerate, these risks are set to increase, especially in coastal areas. And while Early Warning Systems are an essential part of Disaster Risk Management in many regions, they have not been implemented globally yet. In particular, countries in the Global South lack adequate and timely warning systems.

Destination Earth

To gain a deeper understanding of compound flood impacts in coastal deltas and Small Island Developing States (SIDS), Deltares, together with its partners KNMI, Tecnalia and 510 Red Cross (a data and digital initiative that improves speed, quality and cost-effectiveness of humanitarian aid), has developed an innovative compound flood impact modelling workflow leveraging the power of the European Union's Destination Earth (DestinE) program.

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Digital model

Destination Earth is a flagship initiative of the European Commission to develop a highly accurate digital model of the earth (a digital twin of the earth) to model, monitor and simulate natural phenomena, hazards and the related human activities.

The compound flood impact modelling workflow Deltares developed, can be understood as logical order of steps to combine observed data, statistics and numerical models to determine flood impacts, see Figure 1.

Figure 1: Compound flood impact modelling workflow under DestinE, which shows the steps to combine ocean wave models, tide and surge models, and hydrological models for rivers, to compute the compound flood in a coastal area from all sources, with the resultant damage impact computation.

Prepare and respond

DestinE's Global Extreme Digital Twin (DT) and Climate DT provide high-resolution global weather forecasts and continuous climate projections, enabling more accurate and timely flood risk assessments. Our workflow simulates all relevant flood drivers in coastal deltas, facilitates the rapid downscaling of flood models from global to local scales, empowering local communities to prepare for and respond to flood events.

By automating modelling processes with Deltares' advanced software and tools, we empower governmental agencies (DEAL in La Reunion, Environment Agency in UK, URA in Basque Country) to make informed decisions, take necessary precautions, and minimise the devastating impacts of flooding events. This way Deltares contributes to the goal of achieving Early Warning for All globally.

Figure 2: SFINCS flood maps for Humber region for storm Chiara. In the bottom right panel the difference in water depth between the simulations based on ERA5 and the simulations based on DestinE Extremes DT forecast are shown.

Demonstrators

Through five collaborative demonstrators i.e. Basque Country, United Kingdom, Philippines, La Reunion, Dutch Caribbean Islands, we showcase the unique value of DestinE in understanding and acting on compound flood impacts. Our demonstrators encompass diverse regions, including urban deltas, Small Island Developing States (SIDS), and both low-lying and steep coastlines.

They focus on forecasting the impacts of various extreme events, such as tropical cyclones and Northern Atlantic winter storms. By integrating these demonstrators into the DestinE Data Lake, we demonstrate the feasibility of simulating high-resolution flood forecasts within a robust Digital Twin system like DestinE.

Effective decision-making

The Humber Estuary (UK), with its low-lying terrain, dense population, and critical infrastructure, serves as a prime case study for exploring compound flood risks and potential mitigation strategies. They experienced multiple floods with a considerable amount of damage in the past. Together with UK Environment Agency, we explored flood impacts due to high tide and storm surge in combination with heavy precipitation during Storm Chiara (Figure 2).

This helps the EA in improving their flood forecasting system, enabling more effective decision-making and response, such as warning the public, initiate evacuation actions, and implement temporary flood mitigation measures during future compound flood events. Using better and faster forecasting systems makes sure false warnings can be avoided or reduced, and decisions can be made earlier.

La Reunion (FR), characterised by mountainous terrain and an exposed coastline, makes it susceptible to a range of natural hazards. The combined effects of heavy rainfall, and swell waves can trigger impactful flash floods in low-lying areas of the French island. To mitigate these compound flood impact, together with DEAL and CVH who are responsible for flood forecasting, vigilance, evacuation and mitigation in La Reunion, Deltares has applied our compound flood workflow with DestinE data for Tropical Cyclone Fakir (2018) and Tropical Cyclone Bélal (2024). This enables DEAL and CVH to provide robust forecasting results, facilitating rapid evacuation or intervention if needed during upcoming extreme events.

Based on these case studies, the next step is to develop a workflow that is implementable worldwide on any type of coastal system. In this way, Deltares can help making the world safer from flooding.

The Deltares' compound flood impact forecasts, enabled by DestinE, will enhance the Red Cross's ability to deploy humanitarian aid strategically in crisis-prone developing nations. By providing more accurate flood impact forecasts, DestinE enables the efficient allocation of limited resources to the areas that need them most.

Aklilu Teklesadik, Anticipatory Action Service Coordinator at Red Cross Netherlands