Country among worst affected by ground subsidence, threatening heritage sites and spurring suggestions to move the capital

Bita Ghaffari in Tehran and Jana Tauschinski in London

Financial Times

A long-running challenge in Iran has recently taken on added urgency: the ground is sinking beneath people’s feet, damaging vital infrastructure and endangering public safety.

Iran suffers from some of the worst land subsidence in the world, brought on by drought, climate change and poor water management. Cracks threaten the country’s main airport and Unesco sites such as the ancient city of Persepolis, while dozens of schools were evacuated in one city because of fears of collapse last year.

The situation is particularly urgent in and around urban areas including Tehran, where cracks have damaged nearby railway tracks and homes have become unstable.

This prompted President Masoud Pezeshkian to in recent months even moot the idea of moving the capital, saying the “menacing” phenomenon of sinking ground, coupled with acute water scarcity, was making Tehran “unlivable”.

Experts say the long-dormant idea of relocating the capital is impractical. But the intervention from the country’s highest elected official has rekindled debate about the risks posed by a problem that directly affects about half of all Iranians.

“Subsidence has become a huge challenge,” said Mehdi Pirhadi, a member of Tehran city council. He warned the “massive land sinking will destroy infrastructure and threaten lives” unless it was addressed urgently.

Prolonged drought conditions and decades of inefficient environmental governance have intensified subsidence, according to specialists working in the area. One recent global study said Iran was among the world’s top five countries in terms of the extent and rate of subsidence.

Iran’s National Cartographic Centre has calculated that southwestern Tehran was sinking by up to 31cm a year. Even an annual subsidence rate of 5mm is deemed concerning by international standards.

In Tehran’s Shahr-e Ray neighbourhood, people fix their doors and windows every year as subsidence pulls at the foundations, said Mohammad Darvish, an environmental activist.

Main rail lines including those linking Tehran and Mashhad needed to be repaired “many times” because of subsidence, which also caused power transmission towers to tilt and the highway between Isfahan to Shiraz to sink, he said.

The government plans to reduce water consumption in agriculture and industry by 45bn cubic metres a year by 2032 as part of efforts to address the water crisis that exacerbates subsidence. But the cash needed to tackle the problem is hard to come by, as US sanctions throttle the economy.

The scale of the challenge is vast. Subsidence directly threatens 11 per cent of the country’s land mass — an area that is home to almost half of its 90mn people, Iran’s vice-president for environmental affairs Shina Ansari said recently.

Ground fissures have also formed around Persepolis, the ancient Persian capital that dates back 2,500 years, as well as nearby archaeological site of Naqsh-e Rostam, resting place of four Achaemenid kings where massive rock reliefs are carved into a mountain.

Bahram Nadi, a professor of geotechnical engineering at the Islamic Azad University in Isfahan, blamed “untamed urban sprawl, industrial development and excessive farming” in places where dams were already running dry and aquifers depleted. This was not only “accelerating ground-level sinking” but also contributing to desertification.

The subsidence has led cracks to appear in Isfahan’s Unesco-listed Jame Atigh Mosque and some of the buildings and monuments that line Naghsh-e Jahan Square, he said. The eastern and western columns of the square’s Abbasi mosque tilted by 5cm and 8cm and crevices were visible at the stone bases, Nadi said.

Hassan Fartousi, secretary-general of the Iranian National Commission for Unesco, said the UN entity would provide “assistance” to protect heritage sites from subsidence. But he also warned of a worst-case scenario in which Unesco revoked world heritage site titles “if its guidelines are not adhered to and the monuments are damaged”.

The lighter side of Iran’s subsidence problem was highlighted by a recent viral video in which a group of bikers rode inside the dried up reservoir of the Latian dam near Tehran. It is one of four main suppliers of water to the capital and its satellite towns. All are close to running dry.

Mehdi Zare, a professor of engineering seismology at the International Institute of Earthquake Engineering and Seismology in Iran, warned the country appeared to be locked into an “unsustainable” pathway that would only get worse.

“Continuation of past policies in agriculture and urban planning will accelerate subsidence across Iran in the years to come,” he said.