China’s Cities Face Rising Cost Of River Flooding

CHINA IS THE third most vulnerable country to river flooding after India and Bangladesh, with some 3.3 million people at risk, according to data recently published by the World Resources Institute (WRI). It would rank first in terms of absolute GDP at risk, at $18.1 billion a year, though that accounts for a relatively tiny percentage of the country’s entire economic activity.

The rainy season has brought floods since time immemorial. However, in common with other developing nations, China has rising amounts of economic activity exposed to flood risk. More people, buildings, and infrastructure get crammed into vulnerable regions as the country becomes richer and more urbanized. Floods become larger and more frequent because of climate change. The WRI reckons that by 2030, the $18.1 billion of GDP at risk annually will have risen to $94.6 billion. Economic development accounts for $61.6 billion of the increase; climate change for $14.8 billion.

Floods in cities are both more difficult and costly to manage than those in the countryside. Sewers and storm drains are often old and inadequate, run-offs from hard surfaces absent, and ground storage for rainwater scarce. New building covers ever more floodplain. Ancient streams that could absorb overspill from swelling rivers and channel rainwater back to rivers and ponds get filled in. Redressing these problems are huge engineering tasks that cities cannot complete overnight. Beyond that are longer-term policy imperatives: building greener cities that are less encouraging to extreme weather, and not allowing development in flood-prone areas in the first place.

The numbers quoted here come from WRI’s interactive map of flood risk, the Aqueduct Global Flood Analyser (GFA). They assume China has flood defenses adequate to cope with the severity of flooding experienced every ten years. Changing the assumption to 5-year-flood protection levels turns $27.9 billion a year of urban damage into $139.6 billion over the same period. Change it again to 100-year-flood protection, and current annual urban damage falls to $3.1 billion and the 2030 figure to $18.8 billion.

As that range of numbers suggests, the data is intended to provide policymakers with a guide to the cost-benefit of different levels of flood protection. The GFA looks in more detail at six flood prone river basins in China and two coastal plains that are additionally exposed to rising sea levels.

Estimated Flood Damage ($m)

River Basin Flood protection level
10-yr flood 100-yr flood
2010 2030 2010 2030
Yangtze 5,700 25,200 975 4,700
Eastern Coast 5,500 34,800 1,000 7,100
Xun Jiang 2,200 7,600 362 1,100
Ziya River 1,600 10,400 250 2,000
Huang River 1,600 9,000 264 1,800
Bohai 564 4,200 93 1,000
Southern Coast 138 566 24 92
Tarim 19 32 4 6
Source: WRI Aqueduct Global Flood Analyser


From 2011 to 2020, China’s investment in water conservancy projects, which includes flood defenses, is expected to reach 4 trillion yuan ($617 billion). That would be almost four times as much as spent during the previous ten years.

Nature provides lakes, ponds, streams and floodplains to do much the same job. They cannot be sacrificed infinitely in the name of economic development if China is to deal with flooding and its opposite natural disaster, drought. Urban planners are only just starting understand this. This latest WRI data underscores the urgency of the need to protect, restore and reconnect lakes, ponds, streams and floodplains so they can do what they do best.

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