IPCC_Managing Risks of Extreme Events.pdf - Climate Access

Changes in Impacts of Climate Extremes: Human Systems and EcosystemsChapter 4Sahara and Namib Deserts) since the floodwaters infiltrate and rechargealluvial aquifers along ephemeral river pathways, extending wateravailability to dry seasons and drought years (Morin et al., 2009; Benitoet al., 2010), and supporting riparian systems and human communities(e.g., Walvis Bay in Namibia).Damage to African port cities from flooding, storm surge, and high windsmight increase due to climate change. For instance, it is indicated that inAlexandria, US$ 563.28 billion worth of assets could suffer damageor be lost because of coastal flooding alone by 2070 (Nicholls et al.,2008).4.4.2.4. Dust StormsAtmospheric dust is a major element of the Saharan and Sahelianenvironments. The Sahara Desert is the world’s largest source ofairborne mineral dust, which is transported over large distances,traversing northern Africa and adjacent regions and depositing dust onother continents (Osman-Elasha et al., 2006; Moulin et al., 1997). Duststorms have negative impacts on agriculture, health, and structures.They erode fertile soil; uproot young plants; bury water canals, homes,and properties; and cause respiratory problems. Meningitis transmissionis associated with dust in semi-arid conditions and overcrowded livingconditions. The frequency of dust events has increased in the Sahelzone, but studies of observations and in particular studies of projectionsof dust activity are limited (see Section 3.5.8).4.4.3. AsiaAsia includes mega-deltas, which are susceptible to extreme impacts dueto a combination of the following factors: high-hazard rivers, coastalflooding, and increased population exposure from expanding urbanareas with large proportions of high vulnerability groups (Nicholls et al.,2007). Asia can also expect changes in the frequency and magnitude ofextreme weather and climate events, such as heat waves and heavyprecipitation (see, e.g., Table 3-3). Such changes may have ramificationsnot only for physical and natural systems but also for human systems.4.4.3.1. Tropical Cyclones (Typhoons or Hurricanes)Damage due to storm surge is sensitive to any changes in the magnitudeof tropical cyclones (Xiao and Xiao, 2010). For example, changes instorm surge and associated damage were projected for the inner partsof three major bays (Tokyo, Ise, and Osaka) in Japan (Suzuki, 2009). Theprojections were based on calculations of inundations for different sealevels and different strengths of typhoons, using a spatial model withinformation on topography and levees. The research indicated that atyphoon that is 1.3 times as strong as the design standard with a sealevel rise of 60 cm would cause damage costs of about US$ 3, 40, and27 billion, respectively, in the investigated bays.Awareness, improved governance, and development are essential incoping with extreme tropical cyclone and typhoon events in developingAsian countries (Cruz et al., 2007). For example, two cyclones in theIndian Ocean (Sidr and Nargis) of similar magnitude and strengthcaused a significantly different number of fatalities. A comparison ispresented in Case Study 9.2.5.For the period from 1983 to 2006, the direct economic losses in Chinaincreased, but there is no trend if the losses are normalized by annualtotal GDP and GDP per capita, suggesting Chinese economic developmentcontributed to the upward trend. This hypothesis is consistent with dataon tropical cyclone casualties, which showed no significant trend overthe 24 years (Zhang et al., 2009). Similarly, normalized losses fromtyphoons on the Indian southeast coast since 1977 show no increases(Raghavan and Rajesh, 2003).4.4.3.2. FloodingThe geographical distribution of flood risk is heavily concentrated inIndia, Bangladesh, and China, causing high human and material losses(Brouwer et al., 2007; Dash et al., 2007; Shen et al., 2008). Regardingthe occurrence of the extreme events themselves, different floodingtrends have been detected and projected in various catchments, but theevidence for broader regional trends is limited (see Section 3.5.2).In July 2005, severe flooding occurred in Mumbai, India, after 944 mmof rain fell in a 24-hour period (Kshirsagar et al., 2006). The consequentflooding affected households, even in more affluent neighborhoods.Poor urban drainage systems in many parts of India can be easilyblocked. Ranger et al. (2011) analyzed risk from heavy rainfall in the city ofMumbai, concluding that total losses (direct plus indirect) for a 1-in-100year event could triple by the 2080s compared with the present(increasing from US$ 700 to 2,305 million), and that adaptation couldhelp reduce future damages.As noted in the final report for the Ministry of Environment and Forest(2005) of the People’s Republic of Bangladesh, flooding in Bangladeshis a normal, frequently recurrent, phenomenon. Bangladesh experiencesfour types of floods: flash floods from the overflowing of hilly rivers; rainfloods due to poor drainage; monsoon floods in the flood plains ofmajor rivers; and coastal floods following storm surge. In a normal year,river spills and drainage congestions cause inundation of 20 to 25% ofthe country’s area. Inundation areas for 10-, 50-, and 100-year floodsconstitute 37, 52, and 60% of the country’s area, respectively. In 1987,1988, and 1998, floods inundated more than 60% of the country.The 1998 flood alone led to 1,100 deaths, caused inundation of nearly100,000 km 2 , left 30 million people homeless, and substantiallydamaged infrastructure.There have been increases in flood impacts associated with changes insurrounding environments. Flooding has increased over the past fewdecades in the Poyang Lake, South China, due to levee construction254