New York: Adapting to the threat of flooding

Flooding and its effects on infrastructure has been a recent key concern in the UK and with climate change and sea level rise incidences of flooding are expected become more frequent.

New York City skyline
New York City skyline

ICE’s State of the Nation: Infrastructure highlighted that such extreme weather events may mean infrastructure will not be available at society’s expected levels at all times.

This case study is the first in a series examining cities around the world to see how they have managed similar circumstances and what lessons can be learned. The studies are not so much interested in how to build physical/technical solutions, but how policy is developed and resilience and adaptation is planned and delivered.

New York

New York is a coastal/island city with around 600 miles of coastline. It has a population of 8.4 million at a density of 28,000 per square mile (around double that of London). 400,000 New Yorkers live on the city's 100-year floodplain. Although this is only 5% of the population, it represents a greater proportion - and a greater density - than any other city in the US.

The main flooding risk in New York is from surges caused by sudden and intense rainfall. Storms, often caused by the tail-end of hurricanes, can lead to water flows so great they overwhelm drainage infrastructure and result in both above-ground road and subway tunnel flooding. In addition, there is concurrent but lesser risk from sea defences being breached.

Given New York's geography and demography the city is particularly vulnerable to the effects of climate change such as increased frequency of extreme weather events and sea level rise. The New York City Panel on Climate Change projects that by the 2050s, sea levels could be between around 30 and 75 cm higher than at present. As this happens, the risks from severe storms and flooding are also expected to increase.

Indeed, one report states by 2050 what are currently considered 1-in-100 year floods may occur five times more frequently. The number of hurricanes in the North Atlantic Basin, such as Superstorm Sandy, will increase. Moreover, as New York is America's financial and corporate capital, a threat to the city is a threat to the US as a whole.

The issue of flood resilience and planning and its role in anticipating future challenges such as climate change and socio-economic developments is complex. New York has no single readily available flood management strategy.

However, over the past few years, the City of has New York has swiftly and efficiently put in place some of the first and furthest-reaching resilience plans. These are notable both in their evolution from primarily regarding economic development to embracing a more holistic, adaptive approach to climate change and for involving multiple agencies and stakeholders.

Weather impacts and responses

Although originating as a hurricane -the first that had threatened New York since Gloria in 1985 - by the time it reached the city, 2011's Irene had been downgraded to a tropical storm. Its effects included the Hudson River breaking its banks with the subway coming very close to being flooded and the Holland road tunnel being closed due to floods for a day.

Irene was followed by Superstorm Sandy in 2012, which is thought to have been the worst natural disaster to have affected New York: 43 were killed and it caused an estimated $19 billion in damage including flooded roads, subway stations, and electrical facilities, paralysing transportation networks and causing power outages.

The New York Metropolitan Transportation Authority's (MTA) hurricane policy was developed in collaboration with City and State agencies such as the Port Authority of New York, New Jersey Transit and the Offices for Emergency Management and based on lessons learned from Hurricane Katrina that struck New Orleans in 2005.

In addition to the closure of public transport networks, and a number of road tunnels and bridges, prior to Irene reaching New York, the City's Office of Emergency Management ordered an evacuation of 300,000 flood-plain residents.

While there were reported communications failures at the time, such as IT crashes as too many people tried to access City websites, the evacuation itself appears to have been well organised and followed by the public. According to one assessment, this suggests the public expect - and approve of - elected officials who respond promptly and fully to hazard warnings.

For Superstorm Sandy in 2012, having further learned from Tropical Storm Irene, public authorities were better co-ordinated and prepared for a large-scale extreme weather event.

They took the precaution of informing the public three days in advance that an evacuation plan affecting 375,000 people was being enacted8 and public transport would be shut down.

The MTA working with City, State and New Jersey agencies, kept travellers informed of service and infrastructure status updates and initiated its asset contingency plan to minimise damage to infrastructure. This included moving of rolling stock to less flood-prone areas, covering subway entrances, ensuring drains were clear and having recovery crews and equipment in place before the storm struck.

Due to these preparations, there was a relatively speedy recovery of MTA services: the first subway lines ran three days after Sandy with 80% of the system in use after five days. As a result, while Sandy caused significant damage to both life and property, the MTA and related agencies were generally praised for their planning and reaction which was seen as resulting in far fewer casualties than might be expected.

The protection of property and infrastructure was largely due to effective multi-agency co-ordination ahead of Sandy striking, while communication with the public before, during and after also proved invaluable.

Policy approach

PlaNYC, covering investment in green infrastructure including energy, transport and housing up to 2030 was published in 2007. It is a regular programme, updated every four years, setting out biennial milestones, which, in turn, are subject to annual progress reports.

The 2007 PlaNYC was one of the first such reports to recognise the importance of adapting to climate change through an approach that not only considered how one policy area affects another but also how agencies can work together effectively.

Implementation of PlaNYC is the responsibility of the City of New York's Office of Long-Term Planning and Sustainability, an agency specifically created for this task. By 2008 - PlaNYC's first annual update - 92% of the original initiatives were completed or underway.

In response to Sandy, the City of New York's Mayor launched the Special Initiative for Rebuilding and Resiliency (SIRR) to develop the City's plan for rebuilding the hardest hit communities, and to adapt and improve the city's infrastructure. One of its first actions was to develop an unscheduled supplement to PlaNYC with the 445-page report, 'A Stronger, More Resilient New York'.

It details 257 initiatives and is divided into two main parts: the first on improving city-wide systems and infrastructure and the second on rebuilding the areas most impacted by Sandy. Overall, the emphasis is on resilience planning, particularly in order to improve infrastructure to tolerate and resist flooding.

Through strategies for making the city more adaptable to extreme weather patterns, it is intended to be a long-term roadmap for use by current and future administrations. It includes reactive programmes such as the rebuilding of neighbourhoods and proactive measures like reinforcing coastal protection measures with storm surge barriers and soft engineering like tree planting.

By the end of 2013, six months after the report was published, 97% of the 59 near-term milestones and 75% of initiatives were in progress or complete.

Comparing the 2007 PlaNYC to SIRR demonstrates an evolution from a document of general 'green' improvements to infrastructure - something that had been characterised as a wish list - to one with a specific focus; reactive but also preventative. For example, SIRR recommends building on PlaNYC to secure the "cross-silo" institutional capacity to facilitate implementation. needs and increase local capacity.

Criticism of PlaNYC

The first (2007) PlaNYC was drawn up with input from City agencies, academics, and environmental, business and community leaders. It faced criticism on two main fronts.

Some commented it was not really a 'plan' as it did not take into account social aspects such as housing and was vague on economic development, focussing instead on infrastructure. In addition, its use of aspirational milestones rather than metrics was seen as making it difficult to quantify.

This criticism appears unfair as unlike many US cities, New York has never had a full spatial development plan. PlaNYC was not intended to develop new or supplant existing policies on poverty, crime education etc.; rather the focus was infrastructure and how it could be improved to meet the city's future needs.

Others believed PlaNYC suffered because in authoring the report, the City gave consultants McKinsey a central co-ordinating and data gathering role rather than using public agencies.

The report was seen as an "accountants approach" to development rather than one planners would employ. This view was reinforced by perceived limiting of two-way dialogue with residents, which was described by some as "top-down" and "appearing more to appease advocates than invite and influence the shape and content of the plan".

It appears the need for a quick development process to fit in with Mayoral term limits led to the expedient determination to only consult on initial goals not on a full draft of the report.

This view was reinforced by the unusual decision not to seek legislative approval of the final document from City of New York Council (as it was not a spatial development plan there was no need). In turn this led to a perception the recommendations were drawn in secret and were agreed before the report was published and without a draft for consultation.

Criticism of SIRR

Unsurprisingly, given the short timeframes involved, stakeholder engagement for SIRR was modelled on PlaNYC: it was drafted by working with state and national agencies and sought input from elected officials, community groups, and around 1,000 members of the public who participated in technical workshops at the beginning of the process.

Like the previous reports, SIRR operates under the principle of "what cannot be measured cannot be managed"SIRR sets out a series of targets and indicators to be monitored and reported on an annual basis.

As with PlaNYC itself, complaints were made around the level of public consultation both in drawing up the SIRR report and in the planned four-yearly reviews. After the City completed its information gathering, a number of Community Boards - the most local form of governance in New York - complained they and their communities were no longer involved in the decision-making process, making it impossible to affect SIRR's course beyond the initial goal setting.

In response, Community Boards, and environmental justice and labour groups joined together to form the Sandy Regional Assembly, which released a paper criticising the SIRR report on much the same charges levelled against the 2007 PlaNYC.

They highlighted community involvement being conducted as engagement (to make contact with) rather than consultation (to solicit the advice of): there were no significant provisions for public comment on the report's recommendations.

While there have been vocal criticisms of PlaNYC and SIRR, the policies were welcomed by others. An investigation by local news website, Gotham Gazette found 5 of the 11 Community Boards covering the areas worst affected by Sandy thought they were communicating well with the City. In addition, around 150 advocacy groups are members of the City organised Campaign for New York's Future which supports and helps implement PlaNYC.

Nevertheless, it is clear there is a sector of New York citizens who feel they do not have meaningful involvement or ownership over the plans. This could prove to be a problem as, unlike emergency planning where the need for rapid action often necessitates a top-down approach, adaptive resilience planning is long-term and therefore will benefit from more integrative and consultative methods.


Urban infrastructure resilience is not just about building to resist and withstand extreme weather; whether by constructing large schemes such as flood barriers or through soft engineering like tree planting and wetland restoration. Resilience is also about developing and implementing policies.

It is adaption planning as opposed to reactive emergency response; developing proactive schemes and systems and working with rather than imposing administrative structures upon, communities, existing infrastructure and environments.

In the case of an unfolding emergency as seen with Superstorm Sandy, there is a clear argument that the only effective approach is top-down: decisions will often need to be taken and put in place with both haste and speed.

With Irene and Sandy, New York City authorities appear to have made this work: evacuation of a third of a million people and transport shutdowns (and reopening) went as smoothly as can be expected, with communications with the public widely praised – an approach that other major world cities could well learn from.

Citizen participation in developing PlaNYC 2017 and 2011, and 2013's SIRR report is clear but this has not been followed through to the report drafting let alone implementation stages, which require actions not only by public bodies but also by the public themselves. It appears a similar top-down approach has been employed in developing and implementing long-term resilience strategies as with emergency responses.

In drawing up PlaNYC and SIRR there has been some public and community input but there is a risk policy implementation will suffer as it has not been sustained or reviewed to the necessary extent, relying on an engagement rather than consultation model of involvement.

The 2013 SIRR report is effective in the sense that three quarters of the recommendations were put in place within six months of publication. While this swiftness must be applauded it also leads to questions around the decision not to publish a draft report for consultation and only allowing public input at the goal-setting stages.

With this approach and the "what cannot be measured cannot be managed" maxim (although this is not reflected in the report milestones) there is a risk more difficult knotty problems are not included, avoiding deeper, more radical thinking such as managed retreat from low-lying areas.

If all recommendations are 'low-hanging fruit' then each of the annual reviews will be positive but they will lack the long-term focus needed.

While the plans have done well in terms of meeting their initial targets, without community buy-in this is likely to be subject to diminishing returns around continued execution and development.

In terms of the long-term effectiveness of the plans this could prove to be a major difficulty but one that will only become fully apparent when tested by the next extreme weather event.

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