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Eco-Friendly Approaches and Nature-Based Solutions in Coastal Protection

Eco-Friendly Approaches and Nature-Based Solutions in Coastal Protection

 

Ecosystem-based ways to reduce the impacts from disasters and climate change include: green and blue infrastructure, forest restoration, wetland restoration, climate smart agriculture/agroforestry and urban greening. These can be combined with early warning systems or grey infrastructure such as sea walls, if not harmful to the environment.
  • Green infrastructure refers to trees, lawns, hedgerows, parks, fields, forests, etc. Blue infrastructure refers to water elements, like rivers, canals, ponds, wetlands, floodplains, water treatment facilities, etc. These terms come from urban planning and land-use planning. Grey infrastructure refers to built or engineered infrastructure.
  • Hybrid infrastructure encompasses both green and grey approaches, as well as “blue” infrastructure, which mimics natural systems using artificial materials or through combining natural and non-natural structures.
  • Ecological restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed.
     
Conventional vs. Ecosystem-based Coastal Engineering
Conventional vs. Ecosystem-based Coastal Engineering (Temmermann et. al. 2013) by M.Sc. Angelika Gruhn, Prof. Dr.-Ing. Peter Fröhle (CC BY-SA)

 

 

The schematic maps in the figure above illustrate global and regional changes that increase the risk of coastal flood disasters (blue arrows indicate an increase or decrease in intensity of storm waves, storm surge and sea level), and the basic principles of flood protection by conventional coastal engineering (left) and new ecosystem-based defences (right) for an estuary, delta or coastal lagoon (top) and a sandy coast (bottom). In an engineered estuary, delta or coastal lagoon (top left), embankment of wetlands stimulates the landward heightening of storm surges and exacerbates land subsidence (brown arrows) due to inhibited sediment supply and soil drainage.  In the case of ecosystem­ based defence in an estuary, delta or coastal lagoon (top right), wetland and reef creation attenuate landward storm surge propagation and storm waves, and stimulate wetland sedimentation (green arrows) with sea-level rise.For an engineered sandy coast (bottom left), groynes and sea walls may provoke dune degradation due to hindered sand supply, whereas for ecosystem-based defence along a sandycoast (bottom right), reefs help to attenuate storm waves and surge, and off shore sand nourishment stimulates beach and dune sedimentation with sea-level rise (orange arrows).

 
Table: Potentials and Limitation of Ecosystem-based Coastal Defences
Potentials and Limitation of Ecosystem-based Coastal Defences (Temmermann et. al 2013) by M.Sc. Angelika Gruhn, Prof. Dr.-Ing. Peter Fröhle (CC BY-SA)

 

 

Definition of infrastructure types in accordance to their ecosystem functions (Schoones et. al. 2019)
Definition of infrastructure types in accordance to their ecosystem functions (Schoones et. al. 2019) by Sea PiaC, M.Sc. Angelika Gruhn, Prof. Dr.-Ing. Peter Fröhle (CC BY-SA)

 

 

Fundamentals of NbS in Coastal Engineering
There are two main considerations, that determine the applicability of nature-based solutions in coastal engineering.
The first considerations, that need to be taken into account, is the suitability of the considered NbS regarding the hydrodynamic forces and loads. Species and ecosystems in their establishment and existence are limited by a certain maximum hydrodynamic load they can resist. That means, that for the nature-based solutions species and ecosystems should be selected based on their tolerance to hydrodynamic loads. For example, coral reefs and beach systems can resist higher energy level than marshes or mangroves. In cases where hydrodynamic loads create unfavourable conditions for species to survive hard structures or nourishments may be needed. Another related issue, are their habitat requirements. Some species are typically “aquatic”, temporarily aquatic or terrestrial living species. 
The second issue, that must be considered, is the availability for the spatial requirements being needed to obtain the necessary safety level. (Schoones et. al 2019)

References 
  • Schoones, T.; Gijon Mancheno, A.; Scheres, B.; Bouma, T.J.; Silva, R.; Schlurmann, T.; Schüttrumpf, H. (2019): Hard Structures for Coastal Protection, towards greener designs, Estuaries and Coasts, 42(7), 1709-1729, DOI 10.1007/s12237-019-00551-z
  • Temmermann, St.; Meire, P.; Bouma, T.J.; Herman, P.M.J.; Ysebaert, T.; De Vriend, H. J. (2013): Eco-system Based Coastal Defence in the Face of Global Change, In: Nature, Vol 504, Issue 5, DOI 10.1038/nature12859
Eco-Friendly Approaches in Coastal Protection by M.Sc. Angelika Gruhn, Prof. Dr.-Ing. Peter Fröhle (CC BY-SA)

 

 

 

Nature-Based Solutions, Examples from Taiwan by Sea PiaC, M.Sc. Angelika Gruhn, Prof. Dr.-Ing. Peter Fröhle (CC BY-SA)