By 2050, 800 million people will live in cities where sea levels could rise by more than half a metre

Many coastal communities around the world already live with the threat from sea level rise and coastal flooding; where climate impacts can drown neighbourhoods, put people’s lives at risk and wreak economic havoc. But, if the world fails to commit to the Paris Agreement’s goal of reducing carbon emissions and limit global average temperature rise to 1.5oC, many of the world’s cities will face an extraordinary threat from rising seas and coastal flooding by mid-century. According to the new The Future We Don’t Want analysis, the total urban population at risk from sea level rise, if emissions don’t go down, could number over 800 million people, living in 570 cities, by 2050. It is therefore crucial that Paris Agreement pledges are honoured if the social and economic impacts of catastrophic climate change are to be avoided.

Estimates suggest that the global economic costs to cities, from rising seas and inland flooding, could amount to $1 trillion by mid-century. As with other climate hazards, local factors mean that cities will experience sea level rise at different paces. Cities on the east coast of the U.S., including New York City and Miami, are particularly vulnerable, along with major cities in South East Asia, such as Bangkok and Shanghai. In the U.S., east coast cities are witnessing sea level rise that is two to three times faster than the global average while cities along China’s Yellow River Delta are experiencing sea level rise of more than 22 cm (9 inches) per year. According to a 2016 report by Christian Aid; Miami, Guangzhou, and New York are the top three cities in terms of the value of assets exposed to coastal flooding between 2010 and 2070; between 2 and 3.5 trillion dollars. But it’s Kolkata, Mumbai and Dhaka that have the highest number of people at risk from coastal inundation; between 11 and 14 million.

“Hurricane Sandy had a devastating impact across the city … 44 New Yorkers lost their lives, close to 90,000 buildings were in the inundation zone, 2 million people lost power and the city sustained close to $19 billion in damages.” – Jainey Bavishi, Director of Recovery and Resiliency

Figure 1 – Cities a risk from sea level rise of 0.5 metres by 2050s [Cities projected to receive at least 0.5 metres of sea level rise by the 2050s under RCP8.5.]

Cities are at risk of coastal flooding and storm surges

Even though variations in geography leave certain cities acutely exposed to sea level rise and coastal flooding, such as low-lying delta cities in typhoon and hurricane zones, a city’s level of climate risk is intensified by socio-economic circumstances and the built environment’s shape and form. In New York City, some of the most valuable properties in the world are located in flood-prone areas at the southern tip of Manhattan and real estate valued at an estimated $129 billion lies within the city’s floodplains.

When Hurricane Sandy struck New York in 2012, coastal floods impacted an estimated 90,000 buildings in New York City alone, while 2 million people lost power, which caused extensive damage, disrupted commercial activity and costed the city over $19 billion. “The hurricane exacerbated the challenges across the city,” said Jainey Bavishi, New York City’s Director of Recovery and Resiliency, “whether it would be inadequate infrastructure, lack of affordable housing, or existing environmental hazards”. When the waters seeped in over Manhattan, metro stations were flooded and electrical substations submerged, which impacted critical services such as hospitals; several of which had to be evacuated.

While the financial scale of a storm surge impact may be unique in New York, considering the city’s property values and status as a global financial centre, many other cities are dealing with a common problem: How can a city increase its resilience to climate change while simultaneously meeting the housing demands of a rapidly growing, low-income population?

Such is the situation in Dar es Salaam, the largest city in Tanzania. An estimated 8 percent of the city already lies below sea level, which puts over 143,000 people at risk from coastal inundation. But an extremely rapid population growth of 5.3 percent a year means that unplanned informal settlements are expanding into flood-prone areas, where poor residents are highly susceptible to climate impacts. There, the residents’ vulnerability is heightened by inadequate storm water drainage, sewage and piping systems that result in public health hazards during floods.

Neighbourhoods and road infrastructure in Dar es Salaam is frequently inundated, along with river valleys that traverse the city. When it floods, transport systems are disrupted and it can take two to three hours to reach your destination, while the city centre often becomes inaccessible to public transport. Storms and heavy rainfalls furthermore damage electricity poles, which cause regular blackouts, and consequent economic knock-on effects, according to Grace Mbena, Principle Town Planner in Dar es Salaam.

The Indonesian capital Jakarta, meanwhile, flooded in 1976, 1990, 1996, 2002, 2007 and 2012 and is facing similar issues as Dar es Salaam – but at a megacity scale. In northern Jakarta, close to 90 percent of the metropolitan region already lies below sea level, and more than 60 percent of the city’s 10,6 million residents, and particularly the people who live in Kampungs – poor, informal, high-density settlements – are vulnerable to flooding. Based on the experiences and prediction, “every five or six years there are larger floods,” said Aisa Tobing, Senior Adviser, Jakarta Research Council. Jakarta is especially susceptible to sea level rise and high tides since it’s also experiencing one of the fastest land subsidence rates in the world. The digging of illegal wells is deflating the city from below, while the crushing weight of urban sprawl adds additional pressure, causing land to sink by 20 to 25 cm a year; especially in certain areas in North Jakarta.

“Based on climate adaptation research, in 2025, without improving adaptive capacity, more Kampungs will become very vulnerable to climate change.” – Aisa Tobing, Senior Adviser, Jakarta Research Council

In Jakarta, climate change, along with urban development patterns and the geographic condition of being a low-lying delta city, reinforce each other in a troublesome spiral. The result is inundated homes and a paralysed metropolitan infrastructure; along with increased health hazards due to the spread of garbage-laden and highly polluted water. Even without the runaway global warming that would occur by 2050, in the absence of emissions reductions in line with the Paris Agreement, a recent New York Times article points out that hydrologists’ estimation is that Jakarta has 10 years at hand to halt its submergence. If not, millions of residents will be displaced, much of the city’s infrastructure will be wiped out and the country’s economy severely impacted.

Cities & sea level rise infographic

Keeping the waters at bay

Reducing emissions in line with the Paris Agreement would mean that the worst climate scenarios won’t come to pass, but even with limited global warming sea level rise and coastal flooding is bound to get worse.

For all the destruction that Hurricane Sandy brought with it, the climate hazard served as a poignant reminder about the city’s vulnerability – along with the economic importance of keeping New York safe. In the hurricane’s wake, the city government called upon academic experts, the private sector, and regional agencies to strengthen urban policies and plans to reduce climate risk; including impacts from sea level rise and floods. “We’re very lucky in NYC to work with an independent panel of scientists called the New York City on Climate Change (NPCC). They release projections on how climate change may impact New York City every few years and this is mandated by local law,” said Ms. Bavishi. Based on expert advice, New York City has developed a resilience strategy that aims to strengthen costal protection, safeguard critical services and infrastructure, upgrade buildings to withstand future climate impacts, and ensure neighbourhoods are safe and prepared. There was also a new city task force, that worked together with community organisations to better understand the role these organsations played in Sandy recovery efforts. According to Ms. Bavishi, the task force recommended improving coordination among government and community organisations, providing government support for local capacity building of community organizations, and increasing coordination of financial resources for organizations both in advance of, and after a disaster.

New York City is working on protecting its 520 miles of coastline, through a multi-layered approach, focusing on the most vulnerable areas first. The city has completed the Rockaway Boardwalk, which integrates costal protection as a feature, and authorities are currently advancing the final design of a project on the east side of Manhattan, where an elevated park will include a floodwall so that New Yorkers don’t lose waterfront access in one of the city’s most densely populated areas. Other broad measures include an updated building code that accounts for new flood maps and raises elevation requirements for future structures along with a novel zoning designation called “special coastal risk districts”, which limits density in areas that are most at risk.

In Dar es Salaam, the response to sea level rise and flooding has been focused on restricting construction in flood-risk areas to reduce the spread of vulnerable informal settlements. To do so, property rights in less vulnerable areas have been formalised to incentivise families to evacuate flood-prone neighbourhoods. Through regularisations, the city can provide basic infrastructure services such as water supply, storm water drainage, public toilets, waste collection points and transport links. Ensuring that communities become more resilient can be a moving target, though. Relocated households in Dar es Salaam sometimes sell their formalised properties in the upgraded, climate safe areas, and move back to their neighbourhoods of origin. Since the older neighbourhoods may be riskier but have other benefits, such as being located closer to the city centre where connections to markets, hospitals and businesses are better, explained Ms. Mbena.

And when Dar es Salaam attempted to upgrade certain at-risk areas with better storm water drainage, road infrastructure, public toilets and lighting as well as a better police presence for security, through the Community Infrastructure Upgrading Project, property values went up. This rise, in turn, fuelled urban gentrification. The experience in Dar es Salaam shows that finding solutions to climate impacts and pressing housing needs isn’t easy. It requires a continuous conversation with affected communities to better understand and meet the residents’ expressed needs.

In Jakarta, the city has sketched on metropolitan responses as well as neighbourhood measures. “We have short term plans on building a sea wall. For the long run, there are plans to relocate residents at risk” said Ms. Tobing. With assistance from the Dutch government, Jakarta has developed a city-wide climate adaptation strategy that includes a Sea Defense Wall Master Plan. Furthermore, city officials have launched the Socially Inclusive Climate Adaptation for Urban Resilience Project, a five-year effort, that costs $1.3 billion and aims to relocate close to 400,000 people from riverbanks and reservoirs through a participatory process.

“We have short term plans on building a sea wall. For the long run, there are plans to relocate residents at risk.” – Aisa Tobing, Senior Adviser, Jakarta Research Council

Other initiatives prevent the digging of illegal wells, to halt land subsistence, as well as support community-level adaptation in Kampungs. The idea is to integrate community knowledge into city-level adaptation plans, which allows Jakarta to capitalise on residents’ existing knowledge and experience of flood impacts, without having to spend additional government funds on external expertise and costly risk assessments. Through the programme Kampung Climate, Jakarta also encourages competitions between local community leaders to upgrade their green spaces in order to make their communities more resilient. The goal is for green space to make up 30 percent of the city’s land area, a share is on the rise from a low-point of 9 percent. Flooding is still commonplace, but “the time it takes for water to be absorbed and recede is much faster. Before it would take three days but now it takes a few hours,” said Ms. Tobing.

As the varying experiences and challenges in New York City, Dar es Salaam and Jakarta show, climate change and resultant sea level rise and flooding will have diverse impacts based on a city’s geography, urban development pattern, economic makeup and social structure. Despite these variations, however, the broader experience of sea level rise and flooding under business-as-usual climate scenarios will be shared by over 570 cities throughout the world, from Miami to Guangzhou to Mumbai. In cities rich and poor, dense and sprawling, hot and cold, The Future We Don’t Want research shows that unabated climate change will expose 800 million people and trillions of dollars in assets to ever harsher and more frequent climate hazards.

This content is from 2018. View the full “The Future We Don’t Want” report.