Potential for nature-based mitigation of coastal flood risks
18 December 2018
Campus Drie Eiken, Aula Fernand Nédée (Q0.01) - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Biology
Rebecca Van Coppenolle
PhD defence Rebecca Van Coppenolle - Faculty of Science, Department of Biology
Coastal zones are threatened by increasing flood and erosion risks, due on the one hand to sea level-rise and increasing storm intensity induced by global climate change, and on the other hand to the growing coastal population density and associated anthropogenic impacts that aggravate flood and erosion risks. Hence there is an increasing need to implement efficient and sustainable coastal protection solutions. Nature-based strategies, relying on the capacity of coastal ecosystems to reduce the risks of shoreline erosion, attenuate wind waves and storm surges, and to sustain themselves with sea-level rise by biogenic sediment accretion are increasingly proposed and implemented for flood risk mitigation, either as stand-alone solutions or in combination with the standard engineering solutions.
The purpose of this thesis was to define and analyse the spatial distribution of hotspots for nature-based storm surge flood risks mitigation, at regional to global scale.
The creation of a GIS based model assessing the coastal plain area and population benefiting from storm surge mitigation by salt marshes and mangrove forests highlighted that over the world, about 30 % of the flood-exposed coastal plain and 40 % of the flood-exposed population benefit form storm surge mitigation. In general, deltas, estuaries, bays and lagoons present the largest coastal plain areas benefiting from storm surge mitigation. While the highest magnitudes of mitigation are found when large and continuous tidal wetlands are located along the main channels. The amount of coastal population benefiting from storm surge mitigation by tidal wetlands is influenced by the location of the population relative to the tidal wetlands’ location or the population density.
The assessment of the current extent of salt marshes, mangrove forests, seagrass meadows and coral reefs, known to contribute to flood risk mitigation, in front of highly populated and flood-exposed coastal cities shows that 75 % of the 136 studied coastal cities are fronted by existing coastal ecosystems and therefore can potentially benefit from nature-based coastal flood and erosion risks mitigation. Nevertheless, the cities with the largest populations and assets exposed to flooding are generally fronted by small areas of coastal ecosystems. The largest potentially available areas for tidal wetland restoration or creation in front of those cities are found in deltas, estuaries, bays and lagoons. The presence and extent of the different coastal ecosystems as well as the potentially available area to restore/create tidal wetlands is linked to, amongst others, historic, geomorphologic and socio-economic factors.
Via the global analyses presented in this thesis, we demonstrated that despite the various worldwide coastal environments, multiple coastal areas can already benefit from nature-based storm surge mitigation and that this nature-based mitigation could increase with the restoration or creation of coastal ecosystems.