Environmental Engineering Reference
In-Depth Information
Figure 1 Estimated potential sea-level rise by AD 2100, attributable
to principal sources and showing their 'envelope of uncertainty'.
Source: Ince (1990).
Why are we concerned about such apparently modest sea-level rise? Onshore, any
inundation of coastal land threatens human lives, economic activity and infrastructure.
Impacts extend beyond flooding to permanent land erosion, seawater intrusion of
agricultural and urban land, further encroachment of tidal waters into estuaries and river
systems, and higher storm surges. Inshore and offshore, coastal ecosystems and
biodiversity are threatened with loss of habitat, with consequential socioeconomic
damage to communities dependent on the coastline. It is estimated that the human
population directly threatened by coastal flooding due to sea-level rise will be 30 million
by 2020, 90 million by 2050 and over 250 million by 2100. Ninety per cent of those at
risk live in coastal areas of south-east Asia, the Asian Pacific Ocean, West Africa and the
southern Mediterranean Sea. Tangible evidence of risks and losses are evident from the
fact that 70 per cent of the Earth's sandy beaches are retreating, representing 15 per cent
of the global coastline, and the forecast that over 22 per cent of global coastal wetlands
may lost by AD 2080.
Management of these hazards depends on the nature of the coastline, the specific
dynamics of coastal processes, the coastal resource requiring protection and the economic
wealth and integrated planning capacity of the region theatened. Protection by hard
defences (sea walls) or soft defences (beach nourishment) is usually the most expensive
and chosen where the costs or implications of losing infrastructure (such as heavy
industry, nuclear power stations, etc.) are prohibitive (Plate 1). Estimated costs of coastal
protection against IPCC forecast rises exceed US $30 billion in the north-eastern United
States and £5 billion in the United Kingdom.
Accommodation attempts to balance costs by economic diversification away from
flood-prone activities and restriction or prevention future economic development. In
some cases, planners may require the set-back , or removal and relocation, of existing
structures.
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