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ClimateSeverity: High

Subsidence, storm surge and sea level rise in Shanghai

A low-lying delta megacity faces compounding risk from typhoons, storm surge, river floods and rising seas.

Shanghai · China

01 · The problem

What is happening

Shanghai lies on the flat alluvial plain of the Yangtze River delta, with much of the city only a few metres above sea level. Heavy groundwater extraction in the twentieth century caused significant land subsidence; the city has since restricted pumping and reinjected water into aquifers to slow sinking. Typhoons can combine storm surge, high astronomical tides and heavy rainfall, and the IPCC identifies large delta cities as particularly exposed to sea level rise. The city relies on extensive floodwalls along the Huangpu River and coastal seawalls, alongside a national 'sponge city' programme to manage rainfall.

High severity. Serious, widespread effects requiring sustained action. Severity is descriptive editorial metadata summarising documented effects. It is not a measured index or a score.

02 · Causes

Why it is happening

  1. 01

    Historical groundwater extraction

    Pumping compacted sediments beneath the city, lowering ground levels.

  2. 02

    Delta setting and low elevation

    Soft, compressible sediments and low elevation increase exposure to water from sea and rivers.

  3. 03

    Typhoons and extreme rainfall

    Tropical cyclones bring surge and heavy rain, sometimes coinciding with high tides.

  4. 04

    Global sea level rise

    Rising mean sea level raises the baseline from which storm surges occur.

03 · Impacts

Who and what it affects

  1. 01

    Flood risk to dense infrastructure

    Metro systems, ports and high-value districts are exposed to flooding.

  2. 02

    Salt intrusion into water supply

    Low river flows and high tides can push saltwater up the Yangtze estuary toward water intakes.

  3. 03

    Rising costs of defence

    Floodwalls and pumping capacity must be raised and maintained over time.

04 · Solutions

Documented approaches

  1. Groundwater controls and artificial recharge

    Strict limits on pumping and reinjection of water into aquifers.

    Expected effectHas substantially slowed subsidence rates compared with the mid-twentieth century.

  2. Flood defence upgrades

    Raising and strengthening floodwalls and seawalls along the Huangpu and coast.

    Expected effectMaintains protection standards as risks change.

  3. Sponge city measures

    Permeable surfaces, green space and storage to absorb and slow rainfall.

    Expected effectReduces surface flooding from intense rainfall.

  4. Reservoirs in the estuary

    Estuarine reservoirs such as Qingcaosha store freshwater and protect supply from saltwater intrusion.

    Expected effectImproves water supply resilience during salt tide events.

Explore an illustrative What-If

05 · Key indicators

What can be measured

No reliable quantitative indicator is included for this issue. TerraLens shows figures only where a credible source supports them — consult the sources below for current data.

06 · Sources

Where this comes from

  1. [1]Special Report on the Ocean and Cryosphere in a Changing ClimateIntergovernmental Panel on Climate Change · Sept 2019ipcc.ch(opens in a new tab)
  2. [2]Shanghai Municipal People's GovernmentShanghai Municipal Governmentenglish.shanghai.gov.cn(opens in a new tab)

Links open the publishing organisation's site. Some point to the publisher's main page, where the named report or dataset can be found.

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