The Asia-Pacific region is one of the most vulnerable regions in the world to flooding. Over the period of 1986-2006 floods have claimed more than 300,000 lives, and caused an estimated damage to the Asian economy of more than US$200 billion (International Centre for Integrated Mountain Development, 2006). By 2012, floods were the most frequent disaster occurring in Asia (44%) and had the highest human and economic impact. They accounted for 54% of the death toll in Asia, 78% of people affected and 56% of all economic damages in the region. Vulnerability to flooding will increase with rapid urbanization in the region: In 2005 five of the ten most populous cities included Mumbai, Guangzhou, Shanghai, Ho Chi Minh City, and Kolkata. By 2070, nine of the top ten cities in terms of population exposure to climate change floods are expected to be in Asian developing countries. In addition to flood-risks, rapid urbanization in Asia is leading to rapid environmental degradation which in turn is impacting economic growth: In India, the cost of environmental degradation from urban sprawl reduces the country’s GDP by nearly 6%, or around US$80 billion, annually (LSE Cities, 2014). While in China the cost of environmental degradation was estimated to be $230 billion in 2010, or 3.5 percent of GDP.
Global spending on infrastructure and capital projects is estimated to reach US$9tn by 2025, up from US$4tn in 2012: Emerging Asia, including China, India, Indonesia, Malaysia, the Philippines, Thailand and Vietnam will be the fastest growing region, accounting for 47.7% of the global spend by 2025, up from 30.4% in 2012 (Financial Times, 2014). However, with climate change this ‘business-as-usual’ investment in infrastructure will not lead to a stable future according to the World Economic Forum unless it achieves environmental and sustainability goals. Climate change adaptation strategies need to be incorporated into the design and planning phases: To meet the numerous challenges of climate change there needs to be an additional investment of US$0.7 trillion made per year while an additional US$0.1 trillion of spending is required to adapt to the extremes of climate change.
The most common response to storm and flooding risks has been to increase investment in conventional or ‘grey’ infrastructure such as dams and levees to mitigate risks. However, engineers and decision-makers have come to realise the economic and environment costs of these solutions. For example, economically, grey infrastructure is often capital intensive in building, operating, maintaining and replacing. In addition, as grey infrastructure is mainly built to address a specific water management problem it can amplify risks downstream, for example canals may amplify floods downstream resulting in harm to life and damage to infrastructure. Environmentally, grey infrastructure often degrades quality and quantity of water supply from ecosystem degradation. As such, there has been a turn to more long-term economically and environmentally sustainable Green Infrastructure (GI) adaptation solutions that provide equivalent or similar benefits for ‘grey’ infrastructure.
Climate change adaptation involves cities taking action in response to current and projected climate change impacts and vulnerabilities. Actions taken do not have to only consist of protecting society from the negative impacts of climate change, such as sea level rise: instead, actions taken can build resilience to climate change enabling society to not only survive and recover from climatic change but even thrive in a changing climatic environment.
GI involves the use of natural or semi-natural systems that utilise nature’s ecosystem services in the management of water resources and associated risks. GI solutions can be used to support the goals of multiple policy areas. For example, floodplains can reduce flooding risks to cities while simultaneously support agricultural production and wildlife in additional to providing recreational and tourism benefits. Regarding depreciation costs, GI, unlike grey infrastructure, solutions can appreciate in value over time with the regeneration of nature and its associated ecosystem services.
To reduce the impacts of floods, cities can use GI solutions to increase the water infiltration and storage capacity of wetlands and soils. Cities can also mitigate droughts by releasing water from natural storage features such as lakes and aquifers for human and natural use. Specific GI solutions include reforesting along riverbanks, reconnecting rivers to flood plains, constructing green spaces that hold and slowly release floodwater and construction of permeable pavements that enable surface water to infiltrate the soil below. The equivalent grey infrastructure solutions are dams and groundwater pumping, both of which are environmentally and economically costly. GI can also help cities purify polluted water through combinations of sediments, soils and vegetation that filter out sediments and contaminants in water naturally. The equivalent grey infrastructure solution is wastewater treatment plants.
GI can bring about multiple benefits for cities in the Asia-Pacific region including:
- Less damage to infrastructure including water and energy systems: Climate change along with rapid urbanization is leading to more infrastructural assets vulnerable to damage from floods. Specifically, GI can be implemented at the local level to protect various types of infrastructure (e.g. water, energy, telephone systems) from local flooding risks.
- Fewer disruptions to the local economy: By implementing GI cities can reduce the risks of flooding to vital parts of the city such as industrial or commercial zones, ensuring economic activities continue uninterrupted during flooding events.
- Protection of human health: GI can reduce the number of people losing their lives of injured during flooding events by protecting vulnerable areas of cities from flooding events. In addition, GI can be used to ensure water supplies remain contaminant free during flooding events and channel water away to avoid risk of water-borne diseases.
- Increased human security: Urban flooding has the potential to displace people, which can increase the likelihood of conflicts by amplifying drivers of these conflicts such as poverty and economic shocks. GI can ensure urban centres are protected down to the neighbourhood level from flooding events reducing the likelihood of displacement.
- Reduction in poverty: By implementing GI, cities in Asia-Pacific can reduce the likelihood of floods resulting in economic slowdowns, therefore reducing the likelihood of people becoming impoverished from climate change extreme weather events.