Temmerman et al. (2013) - ecosystem-based coastal defence

Question 1

Coastal flood risks are likely to increase over the coming decades owing to…

Answer 1

Global and regional changes that include increasing storm intensity, accelerating sea- level rise and land subsidence.

Question 2

Growing coastal populations mean more people will be exposed to these increasing flood risks…

Answer 2

At least 40 million people and US$3,000 billion of assets are located in flood-prone coastal cities today, and these are expected to increase to 150 million people and $35,000 billion by 2070.

Question 3

Conventional coastal engineering, such as the building of sea walls, dykes and embankments, is widely perceived as the ultimate solution to combat flood risks. However, these defences are seriously challenged in many locations, why?

Answer 3

Their continual and costly maintenance, as well as their heightening and widening to keep up with the increasing flood risk are becoming unsustainable.

Furthermore, conventional coastal engineering often exacerbates land subsidence by soil drainage and hinders the natural accumulation of sediments by tides, waves and wind, thereby compromising the natural adaptive capacity of shorelines to keep up with relative sea-level rise

Question 4

Why is wetland reclamation a risk?

Answer 4

It leads to the loss of storage area for flood waters so that storm surges rise higher and propagate faster and further inland through the remaining channels of a delta or estuary.

In addition, as reclaimed wetlands are cut off from the sea or estuary, the natural process of sediment deposition and land rise is inhibited.

Question 5

Ecosystem-based flood defence has several additional benefits compared with conventional engineering approaches, including…

Answer 5

The improvement of water quality, carbon sequestration, the production of fisheries, nature conservation and the creation of recreational space

Question 6

For example, tidal wetlands improve the water quality of estuaries by…

Answer 6

Delivering scarce nutrients such as silica30 and by acting as a sink for abundant nutrients such as nitrogen and contaminants such as heavy metals.

This improvement in water quality suppresses the growth of toxic algae and stimulates phytoplankton growth, which is essential for the food web

Question 7

Wetlands and reefs promote fisheries production by

Answer 7

Providing an indispensable habitat for juvenile fish, shellfish and crustaceans.

Question 8

There are important limitations to the wider implementation of ecosystem-based flood defences…

Answer 8

These defences tend to require more space than conventional structures.