Risk Assessment of Climate Adaptation Strategies for Extreme Wind Events in Queensland

[摘要] Extreme wind events such as tropical cyclones and severe storms cause extensive damage to coastal and urban communities in Queensland. A changing climate and higher wind speeds means that residential constructions are likely to receive more damage in the future if its design standard is maintained at the current level. The vulnerability of residential construction may be reduced by: (i)Adaptation 1: increases in design wind speeds specified by Australian Standards AS4055-2006 and AS1170.2-2011,(ii)Adaptation 2: retrofitting older constructions (pre-1980) to current standards, or (iii)Adaptation 3: repairing wind damaged houses (pre-1980) to current standards. The economic viability of these climate adaptation strategies was assessed using advanced spatial and temporal stochastic simulation methods that considers the effect of climate change on wind field characteristics, uncertainty of wind vulnerability of houses, costs of adaptation, timing of adaptation, discount rates, future growth in new housing and time-dependent increase in wind speeds with time. On the basis of the latest research in effects of climate change on tropical cyclones, we considered wind climate scenarios ranging from no change to moderate change (25% reduction in cyclone frequency, 10% increase in wind speeds) to significant change (no change in cyclone frequency, 20% increase in wind speeds). A plausible scenario with a poleward shift in cyclones to Brisbane by 2100 is also considered.Results are presented for the various wind change scenarios to 2100 for four cities in Queensland: Cairns, Townsville, Rockhampton and Brisbane. The ‘benefit’ of an adaptation measure is the reduction in damages associated with the adaptation strategy, and the ‘cost’ is the cost of the adaptation strategy. The criteria for cost-effectiveness are: (i)Net Present Value (NPV) or net benefit equal to benefit minus the cost, (ii)probability that NPV exceeds zero or adaptation benefits greater than cost, and (iii)benefit-to-cost ratio (BCR). Key findings are:1.A changing climate can increase mean wind damage losses for Cairns, Townsville, Rockhampton and Brisbane by a total of up to $2.8, $7.1 and $15 billion by 2030, 2050 and 2100, respectively, assuming a 4% discount rate. Moreover, there is a 90% chance that moderate and significant wind change scenarios will increase total damages by more than $1.6 billion and $5.9 billion by 2100, respectively. There is clearly a high likelihood of large potential economic losses, and suggests that climate adaptation strategies are needed to ameliorate these losses.2.Increasing the design wind classifications in the Australian Standard “Wind Loads for Houses” AS4055-2006 for all new housing from 2011 shows great promise as a cost-effective climate adaptation strategy. This means that new construction and alterations would be designed to resist 50% higher wind pressures, resulting in increased strength of building structural components and connections that will lead to significantly reduced wind vulnerability. The adaptation will cost $2.2 billion by 2100 when it is $3,600 per new house, but will reduce wind losses by up to $10.5 billion for the same period. The cumulative NPV for all four cities ranges from $2.3 to $8.3 billion dollars by 2100 for different climate scenarios assuming a 4% discount rate. The NPV for Brisbane is approximately ten times higher than the NPV of Cairns, Townsville and Rockhampton combined. Hence, increasing the wind classification for new housing in Brisbane from Wind Classification N2 to N3/C1 is highly cost-effective with a BCR of up to 5.6 and 80-100% likelihood that a net benefit will be achieved by 2100. 3.The benefits accelerate as time increases, so the NPV of this adaptation strategy is marginal by 2030, but by 2050 can reach $2.6 billion, and by 2100 up to $8.3 billion. Hence, an early investment in climate adaptation will not show an immediate net benefit.

[发布日期] 2011-05-15 [发布机构] CSIRO

[学科分类] 地球科学(综合)