Impact details: increased exposure and vulnerability of coastal communities

impact chain for tropical coastal areas / storms (click nodes to view details):
selected case study results:
Case study reference
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Impact description (case study)
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Das, S. (2012). The role of natural ecosystems and socio-economic factors in the vulnerability of coastal villages to cyclone and storm surge. Natural hazards, 64(1), 531-546. South Asia: India This study examines 262 villages lying within a 10 km of the coast in one of the most cyclone prone districts of India and estimates the probability of expected human fatality due to severe cyclone for these villages. Villages established in mangrove habitat areas (after clearing the forest) and those with more marginal workers (without any regular jobs) were estimated to face a very high death risk. In contrast, villages situated in the leeward side of existing mangrove forests or near a major river are seen to be facing a much lower risk of deaths. The results have important implications like conserving mangroves in cyclone-prone areas, priority evacuation of villages established in the mangrove habitat before a high-intensity cyclone, etc., for cyclone hazard management. To aid decision-making a compact vulnerability map of the coastal regions likely to be affected by climate extremes should be developed.
Das, S., & Vincent, J. R. (2009). Mangroves protected villages and reduced death toll during Indian super cyclone. Proceedings of the National Academy of Sciences, 106(18), 7357-7360. South Asia: India Data on several hundred villages was used to test the impact of mangroves on human deaths during a 1999 super cyclone that struck the state of Orissa. Villages with wider mangroves between them and the coast experienced significantly fewer deaths than ones with narrower or no mangroves. Although mangroves evidently saved fewer lives than an early warning issued by the government, the retention of remaining mangroves in Orissa is economically justified even without considering the many benefits they provide to human society besides storm-protection services.
Badola, R., & Hussain, S. (2005). Valuing ecosystem functions: an empirical study on the storm protection function of Bhitarkanika mangrove ecosystem, India. Environmental Conservation, 32(1), 85-92. South Asia: India Villages protected by the Bhitarkanika mangrove ecosystem suffered significantly less damage than the villages that were unprotected. In the mangrove-protected villages, variables had the lowest values for adverse factors (such as damage to houses), and the highest values for positive factors (such as crop yield). The loss incurred per household was greatest in the village that was not sheltered by mangroves but had an embankment, followed toy the village that was neither in the shadow of mangroves or the embankment. -
Krauss, K. W., Doyle, T. W., Doyle, T. J., Swarzenski, C. M., From, A. S., Day, R. H., & Conner, W. H. (2009). Water level observations in mangrove swamps during two hurricanes in Florida. Wetlands, 29(1), 142-149. North America: USA A hurricane surge acts like a very high tide event that fosters a temporary increase in sea level above the one expected from a normal high tide. Mangrove forests are able to slow the storm surge thus reduce the amount of water reaching inland areas. Recent hurricane strikes along the Gulf Coast of the United States have impacted wetland integrity in some areas but it was also found that mangrove wetlands reduced water level height by as much as 9.4 cm/km inland. Intact mangroves can support a protective role in reducing maximum water level height associated with storm surges. -
Zhang, K., Liu, H., Li, Y., Xu, H., Shen, J., Rhome, J., & Smith, T. J. (2012). The role of mangroves in attenuating storm surges. Estuarine, Coastal and Shelf Science. North America: USA The 6-to-30-km-wide mangrove forest along the Gulf Coast of South Florida effectively attenuated storm surges from hurricane Wilma (category 3), by reducing both the amplitude and extent of overland flooding and protecting the freshwater marsh behind the mangrove zones from surge inundation.
The surge amplitude decreases at a rate of 40-50 cm/km across the mangrove forest and at a rate of 20 cm/km across the areas with a mixture of mangrove islands with open water. In contrast, the amplitudes of storm surges at the front of the mangrove zone increase by about 10-30% because of the blockage of mangroves to surge water, which can cause greater impacts on structures at the front of mangroves than the case without mangroves. The mangrove forest can also protect the wetlands behind the mangrove zone against surge inundation from a Category 5 hurricane with a fast forward speed of 11.2 m/s (25 mph). However, the forest cannot fully attenuate storm surges from a Category 5 hurricane with a slow forward speed of 2.2 m/s (5 mph) and reduced surges can still affect the wetlands behind the mangrove zone. The effects of widths of mangrove zones on reducing surge amplitudes are nonlinear with large reduction rates (15-30%) for initial width increments and small rates (<5%) for subsequent width increments. 		-
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