With growing population and infrastructures the world’s ex- posure to natural hazards is inevitably increasing. This is par- ticularly true as the strongest population growth is located in coastal areas (with greater exposure to floods, cyclones and tidal waves). To make matters worse any land remaining available for urban growth is generally risk-prone, for instance flood plains or steep slopes subject to landslides.
The amount of sediments and nutrients into the ocean from rivers associated with unsustainable land uses, as well as from storms and sewage, also result in the eutrophication of some coastal ecosystems and the coverage of corals by silt or algae, reduced visibility and light in the water column, and hence, subsequently dramatically reduced ability of corals to recover.
Figure 11. Tropical cyclones, or hurricanes or typhoons, are storm weather systems, characterised by a low pressure centre, thunder- storms and high windspeeds. As the name testifies, these occur in the tropical areas. Cyclones can, after they have formed in the oceans, move in over populated areas, creating much damage and even natural disasters. They erode beaches and destroy coral reefs, and loss of natural flood-buffers like mangroves due to coastal development increases damage further.