Climate risks and adaptation in Asian coastal megacities: A synthesis

over the period of analysis. These assumptions aredescribed in chapter 2. Damages costs are evaluatedin Thai Baht and converted to US dollars, using anaverage exchange rate for 2008 of 1 US$ = 33.31 THB.Bangkok likely to witness substantialdamage costs from flooding in 2050, rangingfrom $1.5 billion to $7 billion under a seriesof climate and land use scenariosTable 4.2 presents the costs incurred from damagesto buildings, income losses, health costs, and revenuelosses to public utilities for a range of scenarios.A comparison across scenarios shows that the costsare likely to significantly increase with climate andland use change. In the base case scenario (2050-LS-T10), a 1-in-10-year flood is estimated to resultin damages of 52 billion THB ($1.5 billion), but a1-in-100-year flood with climate change (2050-LS-SS-SR-A1FI) could cost THB 244 billion ($7 billion).The increase in costs from flooding are best illustratedby looking at the implications of a mediumsizedflood. A 1-in-30-year flood in 2008 (2008-T30),for instance, is estimated to result in damage costsof 35 billion THB ($1 billion). In 2050 with climatechange (2050-LS-SS-SR-A1FI-T30), a similar 1-in-30-year flood would cost 148 billion ($4.5 billion) 46 .Thus, in a future climate change (A1FI) scenario, a 1-in-30-year flood in 2050 could lead to a four-fold increasein costs to Bangkok.To illustrate the nature of different costs associatedwith floods, Figure 4.1 breaks down the costsassociated with a 1-in-30-year flood in the future(2050-LS-SS-SR-A1FI). As the figure shows, thedirect costs to buildings are the highest costs borneas a result of flooding, followed by income lossesto commercial establishments.It is useful to understand more carefully therelationship between the costs of hazards such asfloods and the probability of their occurrence. Figure4.2 plots total damage costs to Bangkok fromfloods in different scenarios against the probabilityof their occurrence. As this figure suggests, the costsof damage increase for higher intensity floods, butthis also means that there is a lower probability ofsuch floods occurring. The area beneath each floodexceedance curve represents the average total expectedflood damage cost from floods of differentFigure 4.1 ■ Damage Cost Associatedwith a 1-in-30-year Flood(C2050-LS-SR-SS-A1FI-T30)Damage costs (millions of THB)60,00050,00040,00030,00020,00010,000055,432Residence14045,945CommerceSource: Panya Consultants ( 2009).21,67112,3029,726IndustryIndirect ImpactPublic HealthDamage to Residencial BuildingDamage to Commercial BuildingDamage to Industrial BuildingIncome Loss of Daily Wage EarnerIncome Loss of CommerceIncome Loss of IndustryHealth Care CostIncome Loss of EnergyIncome Loss of Water Supply and SanitationTotal Damage Cost2,012 1,145 13EnergyDirect ImpactWater Supply& Sanitation55,432 MBaht45,94512,30214021,6719,7262,0121,14513148,386 MBahtintensity in any one year. The difference in the areasbetween different exceedance curves representsthe incremental annual damages as a result of a newclimate/land use scenario. These annualized valuesare discussed later in the chapter.Figure 4.2 ■ Loss Exceedance Curves,BangkokDamage costs (mill THB)300,000250,000200,000150,000100,00050,00000.00 0.05 0.10 0.15Probability of flood ocurrence2008 2050-LS 2050-LS-SR-B12050-LS-SR-A1FI 2050-LS-SR-SS-A1FISource: Based on calculations in Panya Consultants (2009).461 USD=33.3133 THB, which was the average exchangerate in 2008.52 | Climate Risks and Adaptation in Asian Coastal Megacities: A Synthesis Report