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In Dead Water

Extreme Weather and Hurricanes Impact Coasts

With growing population and infrastructures the world’s exposure to natural hazards is inevitably increasing. This is particularly 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, thunderstorms 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.

Figure 12. The number of reported extreme climatic based disasters is increasing dramatically worldwide (IPCC, 2006). While part of this increase in the number of weather related disasters, as claimed by some, may be due to better reporting mechanisms and communication, similar increases in reports has not taken place in relation to other types of disasters like the number of reported earthquakes.

Figure 13. During a period between May 1994 to September 1995 the profile of Coconut Beach dramatically changed as a result of storm surges washing away the sand. A rising sea level in the future, combined with more storms, will wash away vulnerable beaches. With the sand gone, the coast is more vulnerable to waves going further inland, threatening fresh water wells with salinisation, leading to land erosion, and making the areas less attractive for tourism. When a beach starts to deteriorate, the process can be amazingly quick. It is very likely that the 20th century warming has contributed significantly to the observed rise in global average sea level and the increase in ocean heat content. Warming drives sea level rise through thermal expansion of seawater and widespread loss of land-based ice. Based on tide gauge records, after correcting for land movements, the average annual rise was between 1 and 2 mm during the 20th century.