The evolution of global flood hazard and risk

Nearly one billion people are exposed to the risk of flooding in their lifetimes. In some areas, such as along the Mekong River in Cambodia, flooding is an annual event. The yearly effects on individuals and societies are extreme.

The EvoFlood project is a £3.7M NERC-funded collaborative research programme addressing this, Earth's deadliest and most costly natural hazard, with the University of Brighton's Professor Phil Ashworth leading on £900K of the project-funding.

Flood processes can be better understood through numerical simulations, with rainfall and inundation as the main components of successful global flood modelling. Accurate estimates of rainfall distribution and intensity are fed into inundation models that reveal what areas will be flooded. The past 10 years has seen notable advances in flood modelling – particularly with respect to rainfall.

By combining recent developments in morphology and connectivity and synthesising these with tools for projecting changes in catchment flow and sediment supply, the EvoFlood project enables delivery of new understanding on how the feedbacks between climate, hydrology, and channel morphodynamics drive changes in flood conveyance and future flooding.

Moreover, the project also connects next generation GFM with innovative population models that are based on the integration of satellite, survey, cell phone and census data. The teams apply the coupled model system under a range of future climate, environmental and societal change scenarios, enabling them to fully interrogate and assess the extent to which people are exposed, and dynamically respond, to evolving flood hazard and risk.

Research aims and questions:

1 Quantify global patterns, trends, and drivers of flooding over the past 40 years; and develop streamflow and sediment climatologies and scenarios of change, to inform the GFM.
Research questions:
> How does floodplain inundation frequency vary spatially across the globe?
> What are the best predictors of floodplain inundation frequency?
> How has the frequency of floodplain inundation changed globally over the past 40 years and what are the drivers of these changes?
> Which catchments are most sensitive to environmental change, in terms of their hydrologic and sediment delivery behaviour?

2 Determine morphological change across a diverse range of river types and climates, building a representation of such changes for inclusion within the new GFM framework.
> What factors control morphodynamic response within river channels and how does this impact conveyance?
> What are the morphological controls on channel-floodplain connectivity and its evolution?

3 Develop and test a new GFM framework and explore sensitivity of flooding
> How do changes in catchment hydrology and sediment supply drive changes in channel flood conveyance capacity, floodplain connectivity and flood hazard?
> Does inundation sensitivity to flood magnitude alter over time, and how are such relationships best parameterised in GFMs?

4 Quantify the evolution of global flood hazard and attribute these temporal changes to different drivers of environmental change
> Where, and by how much is flood hazard changing?
> How and why does this vary from place to place?
> How much of the changing flood hazard can be attributed to morphological as opposed to other (e.g., hydro-climate effects, sea-level rise) drivers?

5 Project global population vulnerability, exposure and response to evolving flood risk
> How does flood risk and vulnerability change in time and space under environmental change?
> How sensitive are the world’s growing population centres to future changes in flooding?
> For specific events, how do population movements respond to (and during) flooding?

Led by Hull University, EvoFlood is a consortium of eight universities including the University of Brighton. It has a large and expert core team, supporting research members and wide-reaching global partners.