A global classification of coastal flood hazard climates associated with large-scale oceanographic forcing

Ana Rueda,Fernando J Mendez,Patrick L Barnard,Paula Camus,Antonio Espejo,Li H Erikson,Peter Ruggiero,Antonio Tomás,Inigo J Losada,Sean Vitousek,Borja G Reguero

doi:10.1038/s41598-017-05090-w

Abstract

Coastal communities throughout the world are exposed to numerous and increasing threats, such as coastal flooding and erosion, saltwater intrusion and wetland degradation. Here, we present the first global-scale analysis of the main drivers of coastal flooding due to large-scale oceanographic factors. Given the large dimensionality of the problem (e.g. spatiotemporal variability in flood magnitude and the relative influence of waves, tides and surge levels), we have performed a computer-based classification to identify geographical areas with homogeneous climates. Results show that 75% of coastal regions around the globe have the potential for very large flooding events with low probabilities (unbounded tails), 82% are tide-dominated, and almost 49% are highly susceptible to increases in flooding frequency due to sea-level rise.

Highlights

For more than a century, attempts have been made to classify the entirety of the terrestrial earth into distinct climate types, e.g. the Köppen–Geiger climate classification system[1]
Each cluster is defined in terms of the tail of the generalized extreme value (GEV) distribution of total water level (TWL), the magnitude of the TWL, the interannual variability, and the predominance of tide, “T”, surge, “S”, or wave, “W”, relative contributions respectively
We introduce the first objective global classification of coastal flood hazard climates

Summary

Introduction

For more than a century, attempts have been made to classify the entirety of the terrestrial earth into distinct climate types, e.g. the Köppen–Geiger climate classification system[1]. We analyze the oceanographic characteristics responsible for coastal flood hazards and obtain a preliminary global classification of so-called coastal flood hazard climates, based on the joint influence of astronomical tides, storm surges, and wave-induced elevated water levels. We apply the total water level (TWL), the sum of the astronomical tide (AT), storm surge (SS), and wave setup (WS), referenced to mean sea level (MSL), as a proxy to represent the maximum potential flood hazard, while recognizing that local topographic characteristics influence the site-specific exposure to this hazard. We obtain a global-scale classification of the primary oceanographic sources of coastal flooding by searching for spatially homogeneous patterns of six physical parameters related to TWL with an automated algorithm. It should be noted that vertical land motion, while clearly a contributing factor to flood vulnerability for many regions[22], is not included in this analysis due to the poor resolution of both large and small-scale patterns and rates, with local variability often playing a dominant role[23]

Objectives

Results

Conclusion