City strengthens flood defenses for extreme weather
November 29, 2012, Thursday
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Print Edition
Print Edition
EDITOR'S note:
Hurricane Sandy's devastation of New York City and the US East Coast has raised awareness of the vulnerability of coastal cities around the world. More extreme weather and rising sea levels are in store. Our reporters Zha Minjie and Ni Yinbin talk to experts and Shanghai authorities about the safety of the densely populated city of 23 million that lies on the East China Sea and in the Yangtze River Delta.
Despite its modernity and expanding infrastructure, Shanghai has a lot of risk factors when it comes to flooding in extreme weather, a reality brought home by the last month's Super Storm Sandy.
Concerns over flood risks were heightened last Tuesday (November 20) when a report to municipal lawmakers said that Shangha's land has subsided by 29 centimeters in the past 40 years or so, creating a geological threat for a city that sprawls an average of only 4 meters above sea level.
Subsidence occurs when ground water is pumped out, often to build foundations for high-rises and to expand Metro lines. City water and flood officials defend the city's ability to stand up to a big storm with flooding.
"With 523 kilometers of coastal levees, the city's flood resistance barriers can withstand a once-in-200-years high tide and cope with gales of up to 133 kilometers per hour," said Hu Xin, deputy director of the Shanghai Flood Control Headquarters. "The levees of the Huangpu River and urban flood control projects enable the city to resist a once-in-1,000-years high tide level of the Huangpu River." (Shanghai Daily, "Official rejects flooding claims," August 23).
He was responding to a report by British and Dutch scientists suggesting that Shanghai - based on geological, hydrological, infrastructure, economic and social criteria - is the most at-risk of nine vulnerable coastal delta cities they studied around the world. Dhaka was second after Shanghai. Rotterdam and Osaka were the least vulnerable.
Hu also emphasized the city's ability to quickly evacuate coastal areas in extreme weather. When typhoon Haikui hit the neighboring Zhejiang Province on August 8, 374,000 people in the outskirts of Shanghai were moved to safety within one and a half days, he said.
The report backed by UNESCO and the Dutch government was not objective or comprehensive regarding the city's drainage and flood control systems, Hu said. The city is constantly upgrading its storm drainage infrastructure, installing bigger and more efficient pipes and pumps, checking seawalls and levees, extending them as needed.
Vast reservoir
Authorities are also considerating a plan to build a vast, 2 million cubic-foot reservoir under Suzhou Creek that would relieve pressure on the system and gradually release rainwater after a storm. And the city's geography is not particularly vulnerable to deep flooding (above two meters) since the terrain is flat, experts say.
In addition, the East China Sea is shallow and the continental shelf is extremely wide, which mitigate the effects of major storms. Annual sea level rise is estimated at around the length of a grain of rice.
Still, there are problems and officials concede the city probably couldn' handle a storm like the one that hit Beijing in July, killing 77 people.
And more extreme weather is predicted around the world because of climate change. The most obvious problem is the city's hardware.
Shanghai's underground system, with its expanding subway network and drainage system of tunnels and pipes, is vulnerable to natural disasters, especially tropical storms that bring downpours and flooding.
The city has 425 kilometers of subway tracks, the world's biggest metro system, and it's still expanding.
Shanghai has 52 million square meters of underground facilities. The city's drainage system capacity is relatively low and sometimes it can barely meet demands during extreme weather.
To be continued tomorrow.
Hurricane Sandy's devastation of New York City and the US East Coast has raised awareness of the vulnerability of coastal cities around the world. More extreme weather and rising sea levels are in store. Our reporters Zha Minjie and Ni Yinbin talk to experts and Shanghai authorities about the safety of the densely populated city of 23 million that lies on the East China Sea and in the Yangtze River Delta.
Despite its modernity and expanding infrastructure, Shanghai has a lot of risk factors when it comes to flooding in extreme weather, a reality brought home by the last month's Super Storm Sandy.
Concerns over flood risks were heightened last Tuesday (November 20) when a report to municipal lawmakers said that Shangha's land has subsided by 29 centimeters in the past 40 years or so, creating a geological threat for a city that sprawls an average of only 4 meters above sea level.
Subsidence occurs when ground water is pumped out, often to build foundations for high-rises and to expand Metro lines. City water and flood officials defend the city's ability to stand up to a big storm with flooding.
"With 523 kilometers of coastal levees, the city's flood resistance barriers can withstand a once-in-200-years high tide and cope with gales of up to 133 kilometers per hour," said Hu Xin, deputy director of the Shanghai Flood Control Headquarters. "The levees of the Huangpu River and urban flood control projects enable the city to resist a once-in-1,000-years high tide level of the Huangpu River." (Shanghai Daily, "Official rejects flooding claims," August 23).
He was responding to a report by British and Dutch scientists suggesting that Shanghai - based on geological, hydrological, infrastructure, economic and social criteria - is the most at-risk of nine vulnerable coastal delta cities they studied around the world. Dhaka was second after Shanghai. Rotterdam and Osaka were the least vulnerable.
Hu also emphasized the city's ability to quickly evacuate coastal areas in extreme weather. When typhoon Haikui hit the neighboring Zhejiang Province on August 8, 374,000 people in the outskirts of Shanghai were moved to safety within one and a half days, he said.
The report backed by UNESCO and the Dutch government was not objective or comprehensive regarding the city's drainage and flood control systems, Hu said. The city is constantly upgrading its storm drainage infrastructure, installing bigger and more efficient pipes and pumps, checking seawalls and levees, extending them as needed.
Vast reservoir
Authorities are also considerating a plan to build a vast, 2 million cubic-foot reservoir under Suzhou Creek that would relieve pressure on the system and gradually release rainwater after a storm. And the city's geography is not particularly vulnerable to deep flooding (above two meters) since the terrain is flat, experts say.
In addition, the East China Sea is shallow and the continental shelf is extremely wide, which mitigate the effects of major storms. Annual sea level rise is estimated at around the length of a grain of rice.
Still, there are problems and officials concede the city probably couldn' handle a storm like the one that hit Beijing in July, killing 77 people.
And more extreme weather is predicted around the world because of climate change. The most obvious problem is the city's hardware.
Shanghai's underground system, with its expanding subway network and drainage system of tunnels and pipes, is vulnerable to natural disasters, especially tropical storms that bring downpours and flooding.
The city has 425 kilometers of subway tracks, the world's biggest metro system, and it's still expanding.
Shanghai has 52 million square meters of underground facilities. The city's drainage system capacity is relatively low and sometimes it can barely meet demands during extreme weather.
To be continued tomorrow.
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