Work Package 1 of the THESEUS project (WP1: Risk assessment, policy, management and planning strategy in study sites) looked at methodologies to define different aspects of the existing coastal flood system (as shown in Figure 1) and assessed the changes in coastal water and river levels associated with climate change; this included the current management status, ecosystems, socio-economic dimensions, uncertainty and warning systems, climate scenarios and flood assessments under present and future climate conditions. This is essential when looking at future changes as this provides a benchmark against which future risk levels can be assessed.

WP1 applied and developed the Source-Pathway-Receptor-Consequence (SPRC) conceptual model, which defines the complete flood system, including potential mitigation options, and hence supports the development of the coastal flood assessments. In developing the SPRC conceptual model, the need for clear communication and understanding between the various scientific disciplines was highlighted. One key benefit was identifying how and where the different scientific approaches and methodologies could interact or inform each other, particularly the more qualitative socio-ecological research. Once developed, the conceptual model was then found to be a useful tool to explain the coastal flood system and its management to stakeholders.

Aspects of the flood system considered in flood assessment as part of THESEUS WP1

Research into existing coastal management policy governance and public perception showed that strong, integrated governance structures are advantageous for coastal flood management. These structures tend to exist where coastal flooding is relatively important in local concerns and risk perception is high among stakeholders, for example the Scheldt, Gironde and Elbe estuaries. However, stakeholders often feel removed from the decision-making process and therefore do not always feel the decisions made are for their benefit. The stakeholder research also showed that the potential role of ecosystems within coastal flood management is not always appreciated. Within WP1, a methodology for assessing the resilience of coastal habitats to the effects of climate change was initiated, which is designed to help recognize alternative/additional management techniques to building of traditional defence structures.

WP1 also looked at climate change as a driver of change in the flood system. A meta-database of wave, surge, sea level and other data with a common basis was created for the eight THESEUS case study sites. This can be accessed through the THESEUS wiki. The data was then used to project future extreme water levels over this century and potential floods in the 2020s, 2050s and 2080s modeled. By looking at the changes in flood extent and frequency associated with these projections, it was found that changes in mean sea level are likely to be the primary influence on future flood events over this century.

WP1 feeds directly into WP5 which is appraising the range of mitigation options in more detail.

Further information can be found in the following THESEUS deliverables:

OD1.7: Homogenous Methods for the Development of Local Scenarios

OD1.10: Report on scenario analysis of drivers and impacts of changing flood risk

OD1.15: Integrated Report on Risk Assessment in the Study Sites

Article by Susan Hanson

Flood Hazard Maps (1990s, 2020s, 2050s, 2080s) for return periods of 100, 1000 and 10000 years, for the Dendermonde area at the Scheldt – Dender confluence.

Maps by Victor Ntegeka, Patrick Willems and Jaak Monbaliu.

Flooding in Cesenatico

The flooding of Bellochio in 2008