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Climate change, water risks and urban responses in the Pearl River Delta, China

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Yang, L. (2014). Climate change, water risks and urban responses in the Pearl River Delta, China. PhD Thesis, Universität Hamburg, Hamburg.

Currently, concerns are increasing that climate change may intensify natural disasters, like droughts, floods and storms which pose risks to human society, especially at the coastal urban area. This thesis studies climate change, water shortage and flood risks as well as human response measures in the highly urbanized Pearl River Delta (PRD) area in South China. Analysis on climate change in the PRD area is based on existing datasets and model projections, with an integration of literature results. Findings indicate significant climate change in both the past and future of the area, with a trend of increasing mean temperature, fluctuating precipitation, rising sea level and increasing typhoon intensity as well as the frequency of extreme weather events. In particular, the annual mean temperature in the PRD area is likely to rise by around 3℃ and precipitation to increase slightly but with greater fluctuations by 2100, while the sea level is projected to rise with an annual rate of 0.33cm to 1cm in this century. Climate change is likely to increase rainfall variability, drought intensity and duration, and damages on water-related infrastructure by extreme weather events, which all increasingly threaten the local freshwater availability. The water supply situation is becoming more complicated along with the population growth, economic development and difficulties in response/management. Hence, ensuring sufficient freshwater availability is one of the major water management challenges for all the PRD cities. Taking Hong Kong as a case study, this thesis highlights six interrelated risks within the context of climate change, namely: drought, rainstorm/flood events, sea-level rise, water pollution, social management and policy gaps. It suggests that for a sustainable future, Hong Kong needs to invest in improving water self-sufficiency, diversify water sources and conduct aggressive public awareness to increase individual adaptation to predicted climate change impacts. Flood implications of climate change trends are pronounced in most of the cities in PRD as well. The frequency and intensity of extreme weather and climate events have assumed significant change, together with continuing development in flood-prone areas, which increase both the scale and degree of urban flood risk. Further estimation was made on the flood risk in the 11 cities of PRD area from both aspects of the probability of a flood occurrence and the vulnerability of the cities. The results suggest that the exposure and sensitivity of Hong Kong, Macao, Shenzhen and Guangzhou are very high because of highly exposed populations and assets located in lowland areas. However, the potential vulnerability and risk is low due to high adaptive capacities in both hard and soft flood-control measures. A novel framework on flood responses is proposed to identify vulnerable links and response strategies in different phases of a flood event. It further suggests that the flood risks can be reduced by developing an integrated climate response strategy, releasing accurate early warning and action guidance, sharing flood related information to the public and applying the advantages of social network analysis. Further, an agent-based model is developed as an instrument to simulate the process by which individual households optimize benefits through flood response investment and damage control. The model implements a subjective response framework in which households appraise inundation scenarios according to warnings, and decide whether to invest in mitigation measures to reduce potential inundation damages. Households may have variant flood response preferences and activities but they all require investments which are consequently considered as part of the final flood losses. A case study was carried out in the Ng Tung River basin, an urbanized watershed in Northern Hong Kong. First results underline that in-time, accurate and wide-covered flood warning plays a significant role in reducing flood losses. And earlier investments in responding measures are more efficient than late activities. This dynamic agent-based modeling approach finally demonstrates its capacity to analyze the interactions between flood inundation and households responses. Overall, findings of this study help understand the level of climate change impacts and vulnerability in water domain, which are vital to gauge the cities’ risks and corresponding responses and therefore inform decisions about how best to deal with emerging climate-related water risks like drought and flood.