Mapping Flood Risks with Future Flow and Precipitation

The United Nations Office for Disaster Risk Reduction estimates that flooding affects 100 million people and results in $14 billion of economic damage every year (average values 1980-2008). Annual economic costs in England are estimated at £1.1 billion, rising to £27 billion by 2080 (National Audit Office, 2011; Office of Science and Technology, 2004). It is widely accepted that flood risk is of major concern globally, and that its management in an uncertain climate is becoming increasingly important. In the UK, mapping of fluvial and pluvial flood extent for the current climatic conditions has been undertaken by the Environment Agency and some local authorities. Within industry, there also exists baseline mapping of areas vulnerable to flooding for risk management purposes. However, with the predicted changes in river flows and precipitation, the frequency and magnitude of future flood events are expected to change accordingly, resulting in uncertainty of future flood risks. Furthermore, given increasing urbanization and land cover changes in the UK, it is likely that the overall exposure to flooding, from various sources, will increase. The decision making of many stakeholders in both private and public sectors relies on a better understanding of future flood risks. However, there are currently limited decision-making or what-if scenario tools for planning and asset management in relation to future flood risks.

This project will develop a prototype mapping service for future flood risks at a test site, focusing on flooding from both the river and intense rainfall. A recently published dataset of projected flow time series will be used to generate future flood risks from the river. A sensitivity-based approach will be used to estimate potential impact of intensified rainfall on surface water flooding. Visualisation and communication tools will be produced to understand end user needs. This project will also evaluate the usability of remotely sensed data for flood risk management, in particular flood modelling. Remote sensing data including, e.g. RADAR, aerial photos and satellite images will be collected for previous events. Data will be used to evaluate their capacity for providing input data for flood modelling and model evaluation. The mapping service is expected to benefit a wide range of stakeholders, including, e.g. (re)insurance industry, utility companies and Local Planning Authorities.

The key stakeholders who will benefit from this project include: (re)insurance industry, utilities companies, Local Planning Authorities (LPA) and the wider risk management sectors.

By integrating Future Flows datasets available from CEH with high-resolution flood inundation modelling at urban locations, the extent and magnitude of future fluvial floods will be predicted. Similarly, an investigation of surface water flood mapping will be undertaken by modelling urban surface water flow routing considering sensitivity-based scenarios of future precipitation extremes. In addition to changes in flow and precipitation conditions, flood modelling will also consider the impact of land use change on flow routing (e.g. through roughness parameter), as well as the impact of flooding on urban land uses. This will enable key stakeholders to benefit. As part of a co-designed delivery process, this will allow better analysis and costing of the impacts of climate-change induced flood risk within the utilities and infrastructure sectors.

(Re)Insurance industry: (Re)Insurance industry faces the challenges of estimating optimal capital allocation in an uncertain climatic and anthropogenic environment. Modelling future flood risks will generate estimate of water depth and velocity at urban locations where properties and assets are located. Using the existing depth-damage curves (Multi-colored Manual), and future flood characteristics generated through numerical modelling, the prototype mapping service will be able to provide updated damage profiles for the point-based property database available at Ambiental.

Utility Companies: Utility companies need to manage their assets and make strategic planning considering future flood risks. The mapping service will enable more resilient and robust management and planning of their assets.

Local Planning Authorities: Currently the decision making of Local Planning Authorities (LPA) is based on flood risk mapping under the current climate and land use conditions. A flood risk mapping service considering changes in both domains will provide a long-term view of flood risks for LPAs.