Engineering and economic impacts of sea level rise

Abstract

Episodic flooding, due to extreme sea levels, can have major impacts on low-lying areas where 10% of the total world’s population resides. Combined with climate change induced sea level rise over the next century, the resulting impacts are likely to be exacerbated. One of the most obvious impact is the exposure of such areas to more frequent and increased extreme sea levels resulting in enhanced inundation extent. Global assessment of extreme sea levels together with the sea level rise component and their impacts is critical to assess the resilience and vulnerability of coastal zones. The present dissertation assesses these impacts on a global scale.

The historical values of tide, storm surge, wave setup are reconstructed from recent reanalyses at global coastal locations. Both the sea levels and the extremes are rigorously validated against quasi-global tide gauge records. To determine extreme values, a variety of extreme value analysis methods are applied and compared against each other and the tide gauge records. Future projections of the extreme sea levels are determined in combination with sea level rise scenarios over the upcoming century. The extent of present and future episodic flooding resulting from the corresponding extreme sea levels are presented. The resulting impacts on the global population and assets at risk for present conditions and under various combinations of future socioeconomic scenarios.

Global "hotspots", based on future changes in the flooding and extreme sea levels, are identified in this study to demonstrate coastal areas which potentially will be the most impacted by changes in extreme sea levels. These areas are mostly found to be concentrated in north western Europe and Asia. The results show that for the case of, no present/future coastal protection or adaptation, and a mean RCP8.5 scenario, there will be an increase of 48% of the world’s land area, 52% of the global population and 46\% of global assets at risk of flooding by 2100.

Regional and national analyses are conducted in order to highlight the values of both Expected Annual Population Affected (EAPA) and Expected Annual Damage (EAD), globally. In order to define a more accurate representation of the global coastal flooding at the aggregated regions, estimated coastal defences are included under various socioeconomic narratives as well as possible adaptation strategies. It is shown that, by 2100 and without future adaptation, global values of EAPA are projected an increase by a factor 3.6 in terms of people impacted. For global values of EAD, the increase relative to present-day values is a factor of 25. It is also demonstrated that the change in the subcontinental regions show significant variations when compared to the present values. In particular, developing areas of Asia will experience significant impacts on both populations and GDP by 2100. These impacts of projected future flooding on the developing world will be far greater than for the developed world.