york flooding case study

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York 2015: Anatomy of a Flood Disaster

York has known devastating flooding many times before and if ever there was a city used to its ravages, its residents have felt it. Time and again, the city’s defences have been improved and adjusted, as new lessons have been learned – but Christmas 2015 raised the bar once again. Over the course of a few days, York suffered its worst flooding in a generation.

Main Image: The Ouse on December 29. Picture: Steve Carroll

Storm Eva unleashed a wave of unprecedented rainfall across the north. Coming just three weeks after Storm Desmond , it exacerbated the ongoing situation , with saturated river catchments responding swiftly to the new deluge.

York Flood Group – made up of the City of York Council, the Environment Agency, North Yorkshire Police, North Yorkshire Fire & Rescue and Yorkshire Water – met on December 27 to discuss the worsening situation. The group usually meets only when the River Ouse levels reach, or are expected to reach, 4.2 meters above normal summer level (asl).

On Monday 28 December, the Ouse peaked at 5.2 metres above its normal summer level, just short of the all-time high of 5.4 metres, recorded in autumn 2000. However, city-wide flooding occurred due to the devastating failure of the Foss Barrier.

It was opened on Saturday 26 December after the pumping station was flooded, leading to floodwaters from the Ouse flowing back into the Foss. The primary concern was the pumps failing due to water ingress to the electrical supply.

The Environment Agency said that if the Foss Barrier were not lifted, it could have jammed in the closed position, causing even worse flooding for 1,800 properties, as water would not have been able to discharge into the River Ouse.

A s a result of the decision, huge areas were flooded for the first time in many people’s lifetimes. Foss Islands Road was closed, Foss Bank and the river were indistinguishable, and several cars parked off Layerthorpe were almost completely submerged.

About 500 homes alongside the Ouse, the Foss, Tang Hall Beck and Osbaldwick Beck were inundated. James Street travellers’ site was also severely hit, with many distraught residents saying they had lost everything.

In total in York, 250 people were evacuated from their homes. Around 10,000 sandbags were used, with 600 military personnel, 125 mountain rescue members, York Rescue Boat teams and countless volunteers helping to rescue flood victims or to fill and distribute sandbags around the flooded areas.

By December 29, the Foss barrier was operational again. The army flew in emergency equipment the day before and repairs were carried out overnight, but by then it was too late for many.

Householders were left counting the cost and many business owners in the city-centre said they were given no warning the barrier was being lifted.

At its height, the flooding caused major knock-on problems.

Floodwaters swamped the basement of the BT telephone exchange, damaging electrical equipment and cutting landline and wi-fi broadband services for thousands of York customers.

People across the city lost phone and internet connections, and many mobile networks failed or struggled, with some people unable to make or receive calls.

Many buildings in the city-centre had no internet or phone connections and most shops, pubs and cafes were able to take cash payments only, as card machines were down.

Picture courtesy of Alfio Fresta

The Jorvik Viking Centre flooded for the first time in its 31-year history, and faced a closure of up to a year . The cells at York Magistrates Court also flooded, meaning many cases had to be moved to other courts.

North Yorkshire Fire and Rescue’s High Volume Pump from Harrogate was used at the Melrosegate Electrical Sub Station to keep it going, preventing 55,000 customers from losing power.

In the end, around 650 homes and businesses had been directly affected by flooding in the city centre. The cleanup cost the council half a million pounds, excluding damage to council assets including properties and infrastructure. It persuaded the government to pay £17m for Foss Barrier improvements and £45m for wider flood risk management improvement works across the city.

The original Foss pumping station was designed to pump about 30 tonnes of water per second from the Foss into the Ouse and was clearly unable to deal with the demand that Christmas.

The upgrade, which will include the installation of eight more powerful replacement pumps, is set to increase its capacity so it can handle at least 40 tonnes per second – securing its performance for the foreseeable future – or until climate change raises the bar again.

Future Climate Info provides a comprehensive flood risk assessment for residential properties through its suite of Environmental Risk Report s . These account for river, sea, coastal and surface water flood extents for a full, clear and effective view on any potential risks ahead of a property transaction.

Based on the assessment, Specialist flood risk services can look at flood resilience measures and a review of flood zoning with climate change allowances can give an accurate appraisal of the likelihood of flooding into the future.

For more information, contact us on 01732 755180 or email [email protected]

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UK Floods Case Study November 2019

The UK experienced an extreme weather event in November 2019 when exceptionally heavy rainfall caused flooding in parts of the UK. Heavy downpours across large parts of northern England led to surface water and river flooding in parts of Yorkshire, Nottinghamshire, Greater Manchester, Derbyshire and Lincolnshire.

According to the Met Office, on Thursday 7th November 2019 over half of the average rainfall for the whole of November fell in parts of the Midlands and Yorkshire.

If you have images and/or videos of flooding or an eye witness account that you would be happy to share on an interactive flood impact map we are developing please send them [email protected]

What caused flooding in the UK in November 2019?

A large area of prolonged rainfall fell on parts of the UK in November 2019. Some areas experienced the whole of Novembers average rainfall over a period of 24 hours. Sheffield experienced 84mm of rainfall. The rainfall was caused by an area low pressure stalling over the UK.

What were the effects the extreme weather in November 2019?

About 500 homes have been flooded in Doncaster with more than 1,000 properties evacuated in areas hit by the floods.

South Yorkshire Fire and Rescue said it had declared a major incident on the evening of Friday 8th November and firefighters rescued more than 40 people from the Fishlake area, near Doncaster. Residents of Fishlake said it was the first time the village had flooded in 100 years.

Empty coffins were seen floating inside the workshop of a flooded funeral parlour in the village.

Some villagers had to spend the night at a nearby pub, where staff said they had seen people crying because of the devastation.

The village church is collecting food to distribute to residents and roast dinners were delivered on Sunday to those who had remained in their homes.

Reseidents have complained that the River Don has not been dredged recently.

According to the BBC, Adrian Gill, a flood manager at the Environment Agency, said did not currently dredge the River Don “because we don’t think that’s the right thing to do” but the situation could be reviewed in the future.

Water sports enthusiast and teacher Mark Ibbotson, from Doncaster, said he, along with his 13-year-old son Logan, had rescued more than 30 people – including two babies – from a number of streets using his inflatable boat in Bentley where homes have been hit by flooding.

One of the most severely hit areas has been Bentley in Doncaster, where flooding affected many homes 12 years ago.

One resident told BBC Radio Sheffield: “The worry is our insurance policies are expensive as it is because of the 2007 floods, so now we’re all worried whether we’re going to get reinsured.”

Extensive flooding affected Rotherham , where residents were told to stay at home and not leave unless asked to do so by emergency services. Some have been taken to safety by boats.

Dozens of people were forced to spend the night in the Meadowhall shopping centre .

In Derbyshire, the River Derwent at Chatsworth reached its highest recorded level and council workers put up sandbags around Matlock and Matlock Bath, where the river was “dangerously high” .

A number of properties in Derby city centre were flooded, however, a full evacuation was not ordered as the River Derwent didn’t burst its banks to the extent emergency services believed it would.

The A52 – the main road route into Derby – was closed westbound between the city and the M1 along with a handful of smaller roads in the county.

Residents from 12 homes in Mansfield, Nottinghamshire, were unable to return home after a mudslide on Thursday led to 35 properties being evacuated .

In Nottinghamshire, residents living in mobile homes close to the River Trent in Newark were urged to move to higher ground.

On Friday, the floods claimed the life of a woman who was swept into the River Derwent at Rowsley in Derbyshire. Her body was found about two miles away in Darley Dale. She was named earlier as Derbyshire’s former High Sherriff Annie Hall .

Trains were cancelled in Yorkshire and parts of the East Midlands as rail routes were flooded.

BBC reporter Richard Cadey said some roads around Fishlake had been closed and the village was “effectively cut off because of flooding”. He said people on the ground had told him 90% of the homes there had been flooded.

The River Don, which flows through Sheffield, Rotherham and Doncaster, hit its highest recorded level at just over 6.3m (21ft), higher than it was in 2007 when it also flooded.

Sources:

England flooding: River warnings and rail delays continue

Flooding in pictures/videos

Torrential downpours flood parts of northern England – BBC

Flooding in Yorkshire – In Pictures – The Guardian

England flooding: A tour of a flooded house in Fishlake

River Derwent Flooding – Drone Video

Helicopter captures footage of flooded South Yorkshire

What were the responses to the UK floods in November 2019?

More than 100 flood warnings were put in place across England. The Environment Agency (EA) urged people to take them seriously.

The Environment Agency took to social media to warn people about the potential impacts of flooding.

AMBER warning for flood risk today ⚠️- rain will rotate over north and north midlands bringing heavy rain on already sodden ground – take care – flood warning updates here https://t.co/K5GUW3z87V pic.twitter.com/mDDAC3uLXc — John Curtin (@johncurtinEA) November 7, 2019

The Environment Agency worked day and night to reduce the impact of flooding. The Environment Agency responded to the flood risk by working closely with police, fire and rescue, local authorities and partners to reduce the risk of flooding and keep communities safe. On the ground, Environment Agency field teams worked through the night to operate flood storage areas and pump away flood water.

A major incident was declared in South Yorkshire,

Some residents were “angry and frustrated” at Doncaster Council – claiming it had not provided sandbags early enough to prevent properties from flooding, the station reported.

Political leaders visited areas affected by floods. On the campaign trail Boris Johnson promised over £2 billion to improve flood defences.

South Yorkshire Police said it had extra officers out on patrol to “protect the evacuated areas and support those affected by the floods”.

Following a meeting of COBRA, the government’s emergency committee, Prime Minister Boris Johnson anounced the following measures :

An extra 100 Army personnel deployed from Wednesday to support the recovery effort in South Yorkshire
Funding for local councils where households and businesses have been affected – equivalent to £500 per eligible household
Up to £2,500 for small and medium-sized businesses which have suffered severe impacts not covered by insurance

Six days after the heavy rain, army personnel provided support to flood-hit communities .

Environment Agency warnings

Environment Agency working day and night to reduce flood impact

How effective were the mitigation strategies introduced since the 2007 floods?

Flood defences put in place in South Yorkshire managed to significantly reduce the impact of Thursday’s floods, the Environment Agency (EA) has said.

River levels in parts of the county rose overnight to almost the same as they were in June 2007, when two people died in Millhouses and the Wicker.

Despite a major incident being declared on Thursday, the EA said the area was protected by new walls and flood gates.

The river levels around Meadowhall were high, but the EA said its defences, as well as the ones put in by Meadowhall, had lessened the damage.

Elsewhere in South Yorkshire, £3m was spent by the EA to repair and improve defences running along Ea Beck , in the villages of Toll Bar and Bentley near Doncaster.

However, people living in settlements downstream of Sheffield have complained about the impact of the recently constructed defences. In Bentley, a low-lying neighbourhood on the north side of the River Don, forlorn terraced streets are still knee-deep in water. “You don’t have to be a hydrologist to see what’s happened,” said one man interviewed by a Guardian journalist . “Sheffield built flood defences in 2015-16. They spent about £20m protecting the lower Don. So the water has nowhere to go than the next place, Rotherham and then Doncaster.” He went on to say that residents received a “red alert” on Thursday night that there was a risk of flooding. He phoned an emergency number and requested sandbags. He was told that the council was not going to distribute them because the River Don’s banks had not been breached.

When the sandbags eventually arrived the community worked together to distribute them.

South Yorkshire flooding: Defences ‘reduce impact’

How do you stop flooding?

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Storm Ciara: York flood defences hold as river peaks

Published 11 February 2020

Flood defences in York have passed their first major test since the Boxing Day floods of 2015.

The Environment Agency said the improvements made since then, including a £38m upgrade of a major barrier, had performed well.

The River Ouse peaked at 4.35m (14.2ft) above normal following the heavy rainfall associated with Storm Ciara.

It's the highest level since 2015, when it reached 5.2m (17ft) above normal.

More from Yorkshire

Martin Slater, from the Environment Agency, said: "It is a test. We've been improving the defences, not only the new barrier and pumping station at the Foss, but also the flood walls that we've increased the height of.

"Everything is operating ok so far."

It was the failure of the barrier, situated where the River Foss drains into the Ouse, in 2015 which resulted in 600 properties flooding in the city.

The barrier is designed to prevent the Ouse forcing water back up the Foss and it also uses pumps to transfer water from the Foss into the Ouse.

It has since undergone a £38m upgrade .

Mr Slater said it was pumping 30 tonnes of water per second from the River Foss into the River Ouse.

He said three flood warnings were still in place in the city and people should "remain vigilant".

Flood warnings also remain in place for villages along the Ouse south of York.

Follow BBC Yorkshire on Facebook , Twitter and Instagram . Send your story ideas to [email protected] .

ESRI UK mapping app protects York from floods

York City Council’s flood team can record, share and visualise information on a hand-held device thanks to Ordnance Survey mapping and ESRI.

York City Council’s flood team can now easily record, share and visualise gully information on any hand-held device, thanks to an ESRI UK app and detailed Ordnance Survey (OS) mapping. This case study explains how it was done.

Partners, products and solutions featured in this study

partner_exchange Esri UK
category OS MasterMap Topography Layer
Keeping the City of York – with an area of 272km 2 and a population of just over 200,000 people – safe from flooding
Developing a quick and cost-effective solution to support the drainage team in their work
Finding an easy-to-use tool that can be used by a range of people, even with no mapping or Geographic Information System (GIS) experience

The council’s GIS team used an ESRI UK app called ‘Collector for ArcGIS’ combined with detailed Ordnance Survey mapping. The gullies data can be added, deleted or removed from a feature class layer, managed by a server using a database connection and a web-based map service.

The data can be accessed via the app using either an Android, iOS or Windows mobile device.

OS MasterMap Topography Layer as a base map gives unrivalled detail at small scale
The council’s business data can be added in a live environment
The app uses the same base map cache as all the City of York’s online apps and flood-risk related data
The app is included with support and maintenance from ArcGIS, so no extra payment is needed
Four flood risk users have added more than 5,000 records in the first eight months
The app is available to all drainage operatives and are used to record maintenance and investigation works
Considerable money was saved developing the app in-house, rather than paying an external supplier
Any changes made to the gullies layer in the app are immediately visible in ArcMap and web-based applications

" This is still an evolving process and with further use we are refining and adapting the app to deliver the key outputs that we require to drive our service forward. In time, wider and more formalised corporate approaches may overtake this system, but its simplicity and ease of use will mean that our expectations of such systems will be greater. This approach has delivered a fantastic range of benefits for relatively little cost. "

Find a Partner to solve your geospatial challenges

Join up with one of our Licensed Partners to create your own success story

Our network of Partners can help you to find the right solution for your geospatial needs and help you to get the most value from OS data. Ranging from global giants to single entrepreneurs, our Partners all use our location data to create innovative products and services.

Esri is a global market leader in geographic information system (GIS) software, location intelligence and mapping, helping customers unlock the full potential of data to improve operational and business results.

OS MasterMap Topography Layer

A map dataset of Great Britain's landscape – from roads to fields, to buildings and trees, fences, paths and more.

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Flood in York city centre in December 2012

The fight against flooding in York

W e have a long history of dealing with flooding in York. Built at the confluence of the rivers Ouse and Foss, and with much of the land in and around the city on flood plains, we are now, out of necessity, well drilled in the disciplines of flood management. York experiences a level of flooding that requires us to implement our first-line flood defences at least two or three times a year.

We've had a strong partnership for over 20 years with the emergency services, Yorkshire Water and the Environment Agency. We've made investments, prepared and implemented flood management plans and learned some tough lessons. In 1982 and 2000, hundreds of properties were flooded and people evacuated , but, with similar water levels in 2012, only 53 properties were affected and no one evacuated .

We used an inflatable to ferry social-care staff to one of our care homes and introduced the Fordlands Ferry – a council truck that ferried residents across a key section of flooded road connecting a community to the city. Huge effort and long shifts from staff, and action from residents, businesses and volunteers kept the city going.

We've worked hard to implement a successful flood response plan and early warning system. We have built a network of incredible volunteers and experienced staff who are ready for action even before flooding occurs. We know those residents in homes likely to be affected and they know our guys on the ground and, critically, who to call for assistance. And we are increasingly using social media to provide instant updates from across the city to keep residents, visitors and ourselves informed.

Last summer, we brought support agencies from across the city together with residents and business to share lessons learned from recent floods. This was a chance to reinforce the messages that there is support available to them before, during and after flooding occurs. We worked with partners to highlight some of the effective measures for protecting homes and businesses, some of which can be done as a community. These include those who supply and install products that offer protection for properties, community-based flood stores (sandbags and flood sacks) and personal flood protection measures such as flood barriers to front doors and air grates. We made available information on alert systems in place through the Environment Agency, Yorkshire Water and the council. We talked about the council's flood relief fund, and support and information on the city's clear-up works. The council has always offered a 100% council tax discount on homes that are uninhabitable and in need of repair due to river flooding. We would expect any properties eligible for council tax discount to be brought back into use within six months, and our inspectors monitor this closely.

The fight against flooding for a city like York will not end. A multimillion pound scheme to help protect 300 residents' homes and businesses from the risk of flooding in an area called Water End is the latest effort under way, backed by council and Environment Agency funding. Central to the development of this scheme has been homeowners and businesses giving their much valued time, thoughts and support in helping us to find the best solution.

On a much wider, national agenda, the council has been lobbying major insurers on issues that residents and businesses have highlighted to us – accessing insurance, ensuring claims are processed quickly and getting replacement items which will proof them against further instances of flooding.

Local government faces the toughest year yet when it comes to questions being raised about whether to continue to deliver certain services and how we deliver them, given the scale of reduction to our funding from government.

We work with our communities to keep York safe from flooding, but ultimately the cost of protecting our communities will continue to be more than we can afford. There will need to be a commitment for continued significant investment from government .

Kersten England is chief executive of City of York council

Local government
Public manager
Communities
Natural disasters and extreme weather
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'Nightmare' flooding hits York after rivers overflow

Published 27 December 2015

Hundreds of people in York are being evacuated as "nightmare" flooding continues to batter parts of northern England.

Six severe flood warnings are now in place across the city after the Rivers Foss and Ouse burst their banks.

Up to 3,500 properties in the city are at risk and between 300 and 400 people are being evacuated.

Several residents near the River Foss are though to be trapped in their homes.

Latest updates from northern England

A man waiting to be evacuated from his home nearby said there were about a dozen people stuck in flats surrounded by water.

"It is really alarming. The whole of town is flooded, it is really extreme - I've never seen anything like this," he said.

"Half of York is underwater."

Residents described the water surging through the city as a "nightmare".

Erica Hammill, who runs Hotel 53 in the Piccadilly area of York, said they are desperately trying to stem the flood damage.

"Our hotel guests are having to climb out of the ground floor windows to get out because the reception area is flooded," she said.

"It's a nightmare. We are getting supplies, sandbags, pumps to mop up the flood damage. But water is coming back in."

Sarah Lakin, who owns The Fossgate Social cafe-bar, had to close last night after water began to flood the cellar. She said the damage was worse on Sunday.

"I've come in this morning and it's right up to the top of the cellar so we're now lifting everything up another floor," she said. "It's a couple of grand [of equipment] gone under water."

Lisa Pallister, 36, was rescued from her home in the Huntington area of the city by boat.

"We didn't think it would reach us because we're raised off the ground and have three storeys but, by this morning, it was on the steps, so we had a boat ride out," she said.

"We're feeling all right. A bit tired, a bit shocked. We're lucky though, a lot of other residents were flooded last night early on."

Janice Findlay has described how water poured into her home.

"The water was coming in a foot every twenty minutes, then another foot, then another foot," she said. "Then we realised we had to get everything out.

"The water then became very dirty, black."

Student Alex Light said the scale of the flooding in the city is worse than previous years.

"The general atmosphere is that it's quite bad," he said. "York has flooded [previously], however it's usually only one of the rivers that floods and this time it's both of them.

"So instead of just a few areas being hit it's the whole city."

York resident Andy Tricklebank said the floods were worse than those suffered in 2002.

"The river has been high for months, so the flooding on top of that has made things worse," he added.

2020 - Safeguarding York from flooding

Posted on 8 May 2012

2020, an experimental short course themed around the issue of flooding in York with representatives from York City Council, the Environment Agency and York Archaeological Trust.

On a balmy afternoon at the end of June, an eagle-eyed observer might have spotted a band of suit-wearing students making their way across campus. This was a gaggle of the Environment department’s first year students on their way to the final session of ‘2020’, an experimental short course themed around the issue of flooding in York, developed by David Rippin and Paul Ayris, and supported by the Careers Service.

The five-day course began with a seminar of invited talks from representatives from York City Council, the Environment Agency and York Archaeological Trust, which gave the students a taste of what was to come. For the rest of the week, they took on the roles of employees of an environmental engineering company, challenged to protect the city from extreme post-climate change flooding. The students worked within groups, getting to grips not only with the complexities of flooding in the city, but also with the issues associated with being in a more corporate environment where things don’t always go according to plan.

On Friday afternoon, the groups gathered together to face down the company’s senior management team and their increasingly-competitive peers, each trying to promote their plan to save the beleaguered city. Although competition was tight, the winning proposal put forward to ‘tender’ was the brainchild of Sam Montague-Fuller, Tamsin French, Rachael Racle, Jordan Walters, Radheeka Jirasinha and Jess Taylor. After a week of hard work, inventive solutions and impassioned debate, each of the groups involved had earned a chance to unwind at the end-of-course reception. Relaxing over a glass of wine, the exhausted ‘environmental engineers’ all agreed that the week had been a great success, and wondered what 2021 might bring.

Department of Environment and Geography Wentworth Way , University of York , Heslington , York , YO10 5NG , UK Tel: work 01904 322999 | [email protected]

Resilient Urban Futures pp 67–84 Cite as

Producing and Communicating Flood Risk: A Knowledge System Analysis of FEMA Flood Maps in New York City

Robert Hobbins 23 ,
Tischa A. Muñoz-Erickson 24 &
Clark Miller 25
Open Access
First Online: 07 April 2021

4640 Accesses

2 Altmetric

Part of the The Urban Book Series book series (UBS)

The burgeoning development of coastal cities coupled with increasing exposure to sea level rise and extreme weather events has exacerbated the vulnerability of coastal communities and infrastructure to floods. In order to make good flood risk reduction and resilience decisions, cities are interested in gaining better insights into what are perceived to be the “real” risks of floods. However, what counts as a good estimate of such risks is constructed through the design of a knowledge system that ratifies certain ideas and methods over others. We refer to knowledge systems as the organizational practices and routines that produce, validate and review, communicate, and use knowledge relevant to policy and decision-making. In this chapter, we conduct a knowledge system analysis of FEMA’s Flood Insurance Rate Maps in New York City. In 2012, Superstorm Sandy exposed in the national spotlight the shortcomings of how we calculate, map, and use knowledge about flood risk. Through this case study, we hope to demonstrate the value of knowledge systems analysis as a method to stress-test and identify the weaknesses of a knowledge system that warrant attention, as well as to inform potential methods ofupgrading or redesigning that system in support of building resilient cities.

Knowledge systems analysis
National flood insurance program
Risk communication
Climate resilience

Download chapter PDF

5.1 Introduction

The burgeoning development of coastal cities coupled with increasing exposure to sea level rise and extreme weather events has exacerbated the vulnerability of coastal communities and infrastructure to floods. One trillion dollars in United States’ coastal assets are currently vulnerable to coastal floods, and sea level rise threatens to expose 13 million people to flooding by 2100 (Reidmiller et al. 2018 ). Extreme events like Superstorm Sandy have revealed the inadequacies of how we calculate, map, and use knowledge about flood risks. National studies have shown that 25% of Federal Emergency Management Agency (FEMA) flood claims lay outside of the FEMA 100-year flood zone (Blessing et al. 2017 ). Several studies report that population growth, gross domestic product (GDP), and climate change have all led to significant changes in flood exposure, and estimate that 41 million people—rather than the 13 million people shown in FEMA flood maps—live within the 100-year floodplain (Wing et al. 2018 ). It is clear that an upgrade, or even a rethinking, is urgently needed in how the United States maps and communicates risks of coastal floods.

In this chapter, we use the knowledge systems analysis framework as a lens to understand the social and technological challenges associated with coastal flood risk analysis, doing so with the objective of informing strategies and innovations needed to overcome those inadequacies. We refer to knowledge systems as the organizational practices and routines that produce, validate and review, communicate, and use knowledge relevant to policy and decision-making (Miller and Muñoz-Erickson 2018 ; Muñoz-Erickson et al. 2017 ). Specifically, we conduct a knowledge system analysis of FEMA Flood Insurance Rate Maps (FIRMs) in New York City (NYC)—the largest coastal city of the Urban Resilience to Extremes Sustainability Research Network—to shed light on the social innovations required to make flood risk mapping work better for homeowners, businesses, and cities given our rapidly changing climate and urban landscapes. Cities are interested in improving their understanding of what are perceived to be the “true” or “real” risks of floods, so as to make and inform good decisions. What counts as a good estimate of such risks, however, is constructed through the design of a knowledge system that ratifies certain ideas and methods over others. Through this case study, we demonstrate the value of knowledge systems analysis as a method to stress-test and identify weaknesses and blind-spots that warrant attention. This analysis informs potential solutions to upgrade or redesign that system in support of building resilient cities.

5.1.1 The National Flood Insurance Program

The principal flood risk knowledge system in the United States is the FIRM produced by FEMA’s National Flood Insurance Program (NFIP). FIRMs are also known simply as FEMA flood maps. The NFIP is responsible for generating knowledge about flood risk within defined zones, which in turn affects decisions about where and how homeowners and businesses build and the flood insurance rates they pay. The NFIP was created by the National Flood Insurance Act of 1968 and made federal flood insurance available for the first time (Michel-Kerjan 2010 ). The Flood Disaster Protection Act of 1973 made the purchase of flood insurance mandatory for those living within the boundaries of high-risk zones—the 100-year flood zone as defined by the NFIP (Michel-Kerjan 2010 ). The initial intent of the program was to provide immediate disaster relief to homeowners after experiencing a flood so they could get back on their feet and move out of the flood zone, ultimately reducing flood risk. Paradoxically, the NFIP instead disincentivized homeowners from moving out of flood-prone areas by shifting the costs to rebuild from the individual to society through heavily subsidized federal flood insurance (Platt 1999 ). Burby ( 2006 ) calls this phenomenon the safe development paradox. Unreliable flood maps (as discussed in this chapter) make this issue even worse when homes in high-risk flood zones are not properly identified and are therefore not required to carry federal flood insurance. As a result, the NFIP does not collect enough insurance premiums to cover its flood claims and has had to rely on tens of billions in government bailouts to remain afloat. Simply put, the NFIP system is broke and broken (Walsh 2017 ).

There have been several notable reforms to attempt to fix the NFIP. The 1994 Reform Act required FEMA to update its FIRMs every five years, though this policy has not been implemented diligently due to stressed budgets, limited administrative staffing, and appeals processes. The 2009 Department of Homeland Security Appropriations Act required FEMA to modernize flood maps by digitizing hand-drawn maps and updating FIRMs to reflect more recent historical climate data. The digitized maps were to be made publicly available through the FEMA Flood Map Service Center. The 2012 Biggert-Waters Flood Insurance Reform Act (BWFIRA) authorized FEMA to update the FIRM to include the best available scientific data regarding future intensities and frequencies of hurricanes, sea level change, precipitation, and storm surge (Grannis 2012 ). The BWFIRA attempted to raise insurance rates to reflect a property’s “true” risk of flooding once a new flood map or update is produced—effectively eliminating the grandfathering process that was federally subsidizing risky properties with taxpayer money. The grandfathering process prevents owners of homes built before a map update from having to pay the full rate required by a new update. Instead, premiums increase over five years by just 20% per year. There was considerable backlash by flood insurance holders to the BWFIRA primarily due to the discontinuation of grandfathering. This political battle resulted in two additional bills which rolled back key provisions in the BWFIRA. The Consolidated Appropriations Act of 2014 prohibited FEMA from implementing Section 207 of the BWFIRA, which directed FEMA to use insurance rates commensurate with their full risk after a FIRM update. The 2014 Homeowner Flood Insurance Affordability Act restored the practice of grandfathering.

5.1.2 Flood Insurance Rate Maps as a Knowledge System

Flood zones are demarcated by FEMA through a highly routinized process. Professional engineers use hydrodynamic modeling to calculate the expected height (i.e., base flood elevation or BFE) and location of floods by waterbodies such as rivers and oceans; the models do not consider floods from infrastructure failures, pluvial floods, or groundwater sources. For inland areas, flood zones and BFE are determined by modeling the overflow of water from streams that have exceeded their capacity during intense precipitation events (i.e., fluvial floods). In coastal areas, flood zones and the BFE are determined by several parameters: current sea level, wave setup, normal high tide, storm surge, and wave effects. Both fluvial and coastal flood modeling utilize digital elevation models (DEM)—typically derived from light detection and ranging (LiDAR) data—for determining the elevation profiles of the study area. The special flood hazard area (SFHA)—for both inland and coastal areas—is defined as the area exposed to a 1% annual exceedance probability (AEP) of experiencing a flood in any given year. This area is often referred to interchangeably by its return period—the amount of time between floods of a certain size. A flood with T year return period will have a 1/T probability of occurring in any given year (Lin et al. 2012 ; McPhillips et al. 2018 ). As such, the return period for an AEP of 1% would be 100 years and the storm would be called a 100-year storm. The 100-year storm standard was selected as a compromise between two competing values: minimizing loss of life by restricting development in floodplains, and keeping floodplains open for economic and urban development (FEMA 2019a ). The AEP is determined using statistical frequency analysis of past storms using historical weather data for fluvial floods, and synthetic storms (created from historical storm surge and tidal records, coastline profiles, and simulated laws of physics) for coastal floods (Sobel 2014 ). The SFHA determines the areas where flood insurance is required and where to enforce floodplain regulations. In addition to the SFHA, flood maps include the areas exposed to a 0.2% AEP storm (i.e., 500-year flood) for reference only. The teal- and black-dotted zones on a FIRM demarcate the 100-year and 500-year flood zones, respectively (see Fig. 5.1 ). A common criticism of this system is that flood risk for a property is often misconstrued as binary—a property is either in a flood zone or out of it (Kousky 2018 ). The 500-year flood zone line on flood maps creates this false sense of security on the other side of that line. To make matters worse, FEMA’s terminology of a 100-year or 500-year flood zone is also misinterpreted by those who are actually aware that they are in one of those flood zones. For those living in a 100-year flood zone, the message received is that their property will only flood once in 100 years when, in reality, FEMA is trying to communicate that the risk is a 1% probability of flooding every year (FEMA 2017 ). For instance, over the course of a 30-year mortgage, a property has a 26% chance of flooding. However, as shown throughout this chapter, that is not the “real” risk either.

Adapted from FEMA ( 2019a ). Lower Manhattan FIRM courtesy of the FEMA Flood Map Service Center (FEMA nd)

The process for creating a Federal Emergency Management Agency (FEMA) flood map. The current regulatory FEMA Flood Insurance Rate Map for lower Manhattan is shown in the center of the figure.

FEMA flood maps are the product of an eight-step iterative process (Fig. 5.1 ) that begins by identifying a project area (Step 1), deciding on a watershed to map or remap (Step 2), and gathering technical data such as hydrological, infrastructural, land use, and population data (Step 3). A Flood Insurance Study is produced and then shared with community officials to review and provide feedback (Step 4). Once the preliminary FIRM is issued (Step 5), the FIRM can be amended or revised through individual or community appeals (Step 6; FEMA 2019b ). Individual property owners can submit a Letter of Map Amendment to provide data showing that their property is not within the SFHA. Community officials can submit a Letter of Map Revision (LOMR) using new scientific or technical data to revise a flood map. Both the LOMA and the LOMR do not actually lead to a physically revised flood map—the changes are documented in letter format only. The Chief Executive Officer (CEO) of a community is the only person who can submit a Physical Map Revision (PMR) to FEMA to physically change the flood zones on a FIRM. Both the PMR and LOMR are typically prepared by experts contracted by local governments. As such, these revisions are costly and resource-intensive endeavors. Once the appeals period expires, a letter of final determination is sent to notify the CEO that the community has six months to adopt a compliant floodplain management ordinance (Step 7) before the new regulatory FIRM becomes effective (Step 8). The case study presented in this chapter will analyze the production, revision, validation, communication, and use of FEMA maps in NYC since 1981.

5.1.3 Knowledge Systems Analysis

Knowledge systems analysis is a useful framework to explore the underlying ideas, rationales, social practices, and institutional structures that define sustainability, resilience, and environmental problems. The framework has been applied to analyze a variety of socio-environmental issues, including sustainability visions (Muñoz-Erickson 2014 ), green infrastructure (Matsler 2017 ), cloudburst flood resilience (Rosenzweig et al. 2019 ), integration of citizen and technical flood risk knowledge (Ramsey et al. 2019 ), and the scalar politics of coastal flood risk (Rozance et al. 2019 ).

Like systems in general, knowledge systems are described in terms of the functions, elements, and complexities of the systems (Miller and Muñoz-Erickson 2018). The core functions of a knowledge system include the production, validation, review, communication, and use of knowledge. For our FEMA case, the process of developing the FEMA flood map is what defines this knowledge system. The steps shown in Fig. 5.1 reflect the various actors involved in how this knowledge system works, including the production of the flood map by FEMA engineers and city leaders (Steps 1 to 3), the review and validation of the maps by local community leaders (Steps 4, 6, and 7), its communication through the issuing of the preliminary FIRM (Step 5) and regulatory FIRM (Step 8), and its use in decision-making processes as to where to build, how high to build, and what flood insurance rates to charge homeowners. Elements of a knowledge system include the content of that knowledge (including its associated uncertainties), the values embedded in that knowledge, the epistemologies (or how we know what we know), and the institutional structures (people and organizations) through which knowledge is constructed and put to use. For the FIRM, knowledge consists of the actual flood maps that are produced and the knowledge claims that are made regarding those maps (e.g., homes in the FEMA 100-year flood zone have a 1% rate of flooding in any given year). Values may include how the knowledge system prioritizes urban and economic development versus restricting development in flood zones, decisions to set risk boundaries in terms of specific flood return periods (e.g., 100-year and 500-year flood zones), and decisions about how to balance historical data and future projections in setting risk zone boundaries. Epistemologies refer to how the problem is framed, types of evidence (e.g., rainfall data from the past 50 years, LiDAR satellite data, etc.), and the information technologies (e.g., hydrological models) used to produce flood maps. Structures include actors or stakeholders that are involved in the functions of the knowledge system. Analyzing knowledge system structures often reveals how power and authority are distributed and the consequences that these arrangements have on the production, communication, and use of knowledge (Muñoz-Erickson and Cutts 2016 ; Muñoz-Erickson et al. 2017 ; Ramsey et al. 2019 ). The role of power and authority in the operations of the FEMA flood map knowledge system in NYC will also be explored in the next section.

5.2 New York City Flood Map Case Study

Our city needs precise flood maps that reflect real risks, both today and years from now, and we have to do that fairly—NYC Mayor Bill de Blasio

To conduct the knowledge system analysis of FEMA flood maps for the NYC case study, we use the framework outlined above to review official FEMA products and documents, reports, academic publications, and newspaper articles containing accounts by various types of flood map users. The above quote by Mayor de Blasio highlights the main aspirations and challenges with flood risk mapping in NYC and the nation. City governments value accurate maps that reflect the “real” risks of floods and communicate reliable information about future flood risk to the public. Yet, city governments also wish to have this risk analysis done in a way that does not place unnecessary burdens on homeowners (e.g., higher insurance premiums or decreased home values) or slow down local economic growth (due to restrictions on development in ever-expanding flood zones). The technical flood mapping process is performed within this negotiation of values and risk tolerance. As such, flood maps are more than just technical products—they are maps with great social implications that warrant care in how they are produced so as to not disproportionally or inappropriately impact any particular social group or sector. At the same time, many hurdles must be overcome in efforts to include future flood risks into FEMA flood map products due to the large uncertainties inherent in future climate and sea-level projections. Through this case study, we use knowledge system analysis to illustrate both the technical and socio-political processes—spanning almost four decades (see Fig. 5.2 )—that went into the production, validation, communication, and use of FIRMs in NYC, and the implications this has for resilience to extreme flood events.

Adapted from PlaNYC ( 2013 )

Timeline of Federal Emergency Management Agency flood map production for New York City.

Superstorm Sandy, which made landfall in NYC on Oct 29, 2012, was one of the worst natural disasters the city has experienced. Sandy was responsible for $19 billion in losses and 43 deaths throughout New York, as well as $65 billion in losses and 159 deaths nationwide (PlaNYC 2013 ). Sandy’s storm surge of 14 + feet (ft) left parts of NYC in ruins and nearly two million residents without power for up to two weeks (PlaNYC 2013 ).

The damage from Sandy resulted from a storm surge that was the highest in the historical tide gauge record—extending as far back as 1850—and exacerbated by a seasonal high tide that inundated areas well beyond FEMA flood zones. As seen in Fig. 5.3 , sea level rise also played a small but significant role in contributing to the record flood height. At the time of Sandy’s landfall, the flood maps were grossly outdated—they did not reflect changes in climate and sea levels (see Fig. 5.4 ), rapid land-use change, or advances in technology such as the development of more accurate elevation profiles from LiDAR (Parris 2014 ).

Relative sea level trend as measured from The Battery tide gauge station in NYC. Plotted values are monthly averages. The historic rate of sea level rise is 2.85 mm/year, or about 1 foot every 100 years (National Oceanic and Atmospheric Administration 2019 )

The regulatory flood maps for NYC have not received a significant update since 1983, despite the legal requirement for flood maps to be updated every five years. From 1991 to 2007, flood map updates included new wetland and stream modeling but failed to include any elevation adjustments. In effect, these were very minor modifications to the original 1983 floodplains. The results were placed on satellite imagery, digitized, and made available online for general public consumption in 2007. Concerned about the inaccurate flood risk information being communicated to the public, local and state officials immediately called on FEMA to perform a full map update using the best scientific data and technology available. The update process did not begin until 2009 and had yet to be completed before Sandy struck in October of 2012 (see Fig. 5.2 timeline).

The 2007 FIRM underestimated the scope of inundation that awaited the city during Sandy. Only 54 and 47% of the flooded area in Queens and Kings, respectively, was predicted by the 1983 flood maps during Sandy (Shaw et al. 2013 ). Figure 5.5 shows the vast swaths of the city inundated by Sandy, yet left out from the 1983 FIRM 100-year floodplain. However, Sandy was not calculated to be a 100-year storm; it was estimated by using outdated historical climate data to be a 1,000-year storm (Lin et al. 2012 ). However, several authors argue that climate change helped to intensify Superstorm Sandy (Dietrich 2017 ; Parris 2014 ; Sobel 2014 ). Increases in sea levels alone could have accounted for half a foot of flooding during Sandy (Parris 2014 ; Shaw et al. 2013 ). Lin et al. ( 2012 ) show that when taking into consideration changing climate and increasing sea levels, the current 100-year storm surge event in NYC has the potential to occur every 20 years or less and the present 500-year event has the potential to occur every 240 years or less by 2100. Thus, there are strong reasons to update flood maps regularly to reflect changing climate and sea levels. If the FEMA flood maps had been updated prior to Sandy to incorporate recent SLR and extreme precipitation and flooding events (e.g., the March 2010 nor’easter and Tropical Storm Irene in 2011), they may have more accurately reflected the extent of flood risk during Sandy and improved flood risk communication and resilience outcomes.

1983 federal emergency management agency flood insurance rate map and Sandy inundation area comparison (PlanNYC 2013 ). Image used with permission of the New York City Department of City Planning. All rights reserved

After completing the Coastal Flood Study for New York in 2009, FEMA issued the 2015 Preliminary FIRM (P-FIRM) for NYC using new LiDAR data, more recent climatological data (e.g., Tropical Storm Irene and Superstorm Sandy were both included), and more sophisticated hydrologic modeling. The 2015 P-FIRM nearly doubled the building stock located in the 100-year flood zone from 36,000 to 71,500 units (City of New York Mayor’s Office of Recovery and Resiliency 2015 ). Nearly twice as many New Yorkers would be required to pay for mandatory flood insurance after this update. The P-FIRM had the potential to aggravate the affordable housing crisis in NYC by expanding the reach of mandatory flood insurance and increasing existing premiums (Dixon et al. 2017 ). Consequently, the news was not welcomed by affected homeowners (Chen 2018 ). Under public pressure to keep housing and insurance rates affordable, NYC pushed back by filing an appeal of the 2015 P-FIRM on scientific and technical grounds (Chen 2018 ). The City’s appeal was politically motivated, but had to be filed on scientific and/or technical grounds—FEMS’s epistemology for creating and revising flood maps. As discussed in the section entitled “Flood Insurance Rate Maps as Knowledge Systems,” the Chief Executive Officer of a community has the sole legal authority to challenge FEMA’s flood mapping expertise. The appeal must also be submitted within a 90-day period after a P-FIRM is issued. The New York City Mayor’s Office contracted outside engineering firms, which included the design and consultancy firm Arcadis, to conduct the City’s flood analysis. NYC’s appeal claimed that scientific and technical errors—insufficient extratropical storm model validation and misrepresentation of tidal effects of extratropical storms—lead to the P-FIRM overstating the BFE by over 2 ft in many areas and presenting 35% larger SFHA boundaries (City of New York Mayor’s Office of Recovery and Resiliency 2015). However, NYC elsewhere claimed that the initial reason for the appeal was that “the revisions will assist New York City in making coastlines more resilient and climate ready, while ensuring homeowners are not required to purchase more insurance than their current flood risk requires” (City of New York nd). The appeal was an attempt to reduce the extent of the new SFHA and BFE in the P-FIRM (the political goal) while also updating the maps with more recent climate and storm data (the resiliency goal). Rather than 71,500 buildings in the SFHA, the new NYC analysis reduced the number of units to just 45,000—a 37% reduction—as shown on the P-FIRM. The appeal also provided extra time before an update could be issued—effectively saving property owners money as their insurance rates and requirement to purchase flood insurance would continue to be based on the 2007 FIRM SFHA boundaries. The City’s appeal was successful. FEMA agreed in 2016 to revise the maps according to the City’s analysis. However, as of December 2019, FEMA has still not issued any update to NYC’s FIRM. As such, there are now three competing knowledge claims regarding claims regarding New Yorkers’ FEMA-delineated flood risk, leaving residents in limbo regarding this risk (e.g., the current regulatory 2007 FIRM, the 2015 Preliminary FIRM, and NYC’s flood analysis). While the City’s political goal may have been achieved through this appeal, this state of uncertainty is a failure of the flood mapping knowledge system to clearly, timely, and definitively communicate flood risk to property owners for their individual resilience and adaptation decisions. For instance, a prospective homebuyer may unknowingly become vulnerable to floods by purchasing a new home that is within the SFHA on NYC’s flood analysis, but does not fall within this zone according to the 2007 FIRM—the map currently used to determine flood risk for a property. For instance, many residents of Staten Island—one of the hardest hit places during Sandy—expressed frustration that they did not know their properties were at risk of flooding at the time they purchased their homes (Moore 2018 ). The Morgan family—whose basement was destroyed in Sandy—said they would have at least moved their utilities out of the basement had they known Sandy was predicted to bring 11 ft of flooding—as shown on the P-FIRM—compared to the less than 1 ft shown on the 2007 FIRM (Shaw et al. 2013 ).

In contrast, there is actually a clear and definitive standard for resolving these competing flood risk knowledge claims for use in building construction at the city level. NYC adopted Local Law 96/13 which modified the City’s building code to require all work permits for construction projects to be based on the more restrictive BFE and SFHA of either the 2007 FIRM or the P-FIRM (NYC Buildings 2014 ). Additionally, the NYC Commissioner of Buildings issued a rule in 2013 that for buildings in the SFHA, 1 to 2 ft must be added to the BFE in order to determine the Design Flood Elevation (DFE). No dwelling units or mechanical equipment (e.g., electrical and HVAC systems) are permitted in floors below the DFE (New York City Planning Department 2013 ). By decoupling the P-FIRM from insurance rate hikes, NYC was able to make use of this valuable knowledge for construction decisions without imposing new or higher flood insurance costs on residents.

While the P-FIRM and NYC’s flood analysis incorporated more recent climate data, these maps still do not incorporate any anticipated future flood risk (e.g., sea level rise) for long-term residential or urban planning decisions. NYC addressed this knowledge gap in 2008 by creating a new knowledge system separate from the NFIP. The New York Panel on Climate Change (NPCC) is a panel of experts created by the NYC Mayor’s Office to provide analysis of future climate change impacts such as extreme floods. FEMA is now collaborating with the NPCC to create “innovative, climate-smart flood maps” for NYC that incorporate the best available science regarding future sea levels and coastal storms for long-term planning and building purposes, while updating the FIRM to depict current risk for insurance purposes (FEMA 2016 ). The NPCC recently published its projections of NYC’s floodplain for 2100 and compared it to the 2015 P-FIRM (Patrick et al. 2019 ). The results indicate that the floodplain is likely to expand as NYC experiences additional sea level rise and more intense storm surges (Fig. 5.6 ).

Projected 100-year floodplain through 2100, as compared to the 2015 Preliminary Flood Insurance Rate Map (Patrick et al. 2019 )

The NPCC’s anticipatory flood maps are not yet required for NYC’s long-term planning decisions, but the City now has access to this valuable knowledge. While the NPCC has been helpful for the City to understand their future flood risk, individual New Yorkers are still largely in the dark. NYC has recently created a new position, Deputy Director of Climate Science and Risk Communication, to serve as a City liaison to the NPCC. There is hope that the creation of this new position may help communicate the NPCC’s forward-looking flood risk maps to the general public.

The strategy of decoupling flood risk knowledge from insurance rates is at the core of this knowledge innovation for anticipatory flood resilience decision-making in NYC. Access to resources—money and experts—were also essential. NYC had the resources to convene the expert NPCC panel to produce this knowledge for the City’s planning and decision-making. Yet, few cities have NYC’s financial and university resources to be able to create an entirely new knowledge system—such as the NPCC—to augment the inadequate FEMA flood maps. From a social justice and equity perspective, it is important that FEMA step in to provide access to future-looking flood risk knowledge for resource-scarce cities. However, there is not a clear path forward for how FEMA will communicate future risks of flooding for community resilience and adaptation decisions. FEMA has been authorized to provide maps of future flood risk since the BWFIRA was enacted in 2012. However, the FEMA Technical Mapping Advisory Council’s efforts have been stalled and their final report withheld, preventing legally binding guidance on how FEMA should move forward with communicating future flood risks. In the following section, we discuss some possible options for redesigning the NFIP based on this knowledge system analysis of NYC flood risk mapping.

5.3 Discussion and Conclusion

Understanding how the FEMA flood map knowledge system works is essential for the adaptive capacity and resilience of cities to climate change and extreme events. These maps guide a myriad of important decisions affecting urban form and community resilience both now and in the long-term future. Homeowners use this information to make individual decisions such as whether to buy a home, carry flood insurance for a home, how high to elevate a home, or simply whether or not to move a generator or other appliances out of their basement or ground floor. Developers use this information to decide where to build and the design of the building. City engineers use this information to determine where and how to build critical infrastructure throughout the city. As the U.S. Department of Homeland Security Office of the Inspector General (DHS OIG 2017 ) reported, it is imperative that we provide accurate and reliable flood risk information to the public, and this will require changes to the flood mapping process, management, and oversight. In essence, the DHS is calling for a knowledge system upgrade or redesign to modernize the flood mapping process given its expanded user network and salience.

As we have shown with the NYC case study, the FEMA flood map knowledge system has several social-political and technical challenges associated with it, including outdated climate data, lack of anticipatory flood risk knowledge, difficult to interpret and communicate flood risks, lack of consideration of infrastructure or pluvial floods, politically motivated map revisions, a resource-intensive and inequitable revision process, and so on. How well a knowledge system produces quality knowledge for decision-making is not simply a matter of collecting the best scientific data and using the most sophisticated technology to produce a flood map; the distribution of power and authority also greatly influences the quality and accuracy of the knowledge claims produced by the knowledge system (e.g., the SFHA boundaries and BFE of the P-FIRM and NYC flood analyses). In NYC, the social (e.g., the formalized and routinized process of creating map products) and political (e.g., who wins and who loses from map updates, who has authority to challenge flood map knowledge claims, etc.) dynamics have played key roles in the production, review and validation, communication, and use of flood maps over the past four decades. Any redesign will need to address both the social-political and technical aspects of this knowledge system.

You might ask, what would an upgraded or redesigned flood mapping system look like and how could it be accomplished? The low-hanging fruit for an upgrade would be for FEMA to include non-regulatory future flood risk knowledge alongside their official regulatory map products; this would effectively decouple this information from determining insurance rates. As shown in the NYC case study, by decoupling the P-FIRM from insurance rates, NYC was able to use this valuable knowledge for building construction and zoning decisions to improve the long-term flood resilience of the City’s built environment. A more transformative change to the entire flood mapping system would be to retire the use of the 100-year and 500-year flood zones given the well-documented misconceptions users have and the false sense of security they give to residents living outside of these zones. This technical change will also be inherently disruptive socio-politically as new federal legislation would need to be written and the entire NFIP—which provides disaster relief to flood victims—would need to be dramatically revised to accommodate this change. This redesign would likely require new legislation from the U.S. Congress. It would also likely require a shift in the values underpinning the knowledge system—which are notoriously difficult to change. Given the magnitude of recent flood disasters like Hurricane Katrina, Superstorm Sandy, Hurricane Harvey, and Hurricane María, it may become necessary to value the protection of lives and property more than is currently done relative to the value accorded to urban development and growth. The Special Hazard Flood Area—which restricts development in the 100-year flood zone—was chosen as a balance between these two values. The NFIP may require a recalibration of our nation’s flood risk tolerance and values in order to fix this broken and broke program.

In closing, our analysis of how the FEMA FIRM knowledge system works sheds light on the underlying complex social and political dynamics involved in how we know, review and validate, communicate, and use flood risk knowledge. Knowledge about flood risks is more than the map that results from collecting data and running models to determine “real” flood risk for a property; it is the outcome of a highly contested co-production process between individual residents, experts (e.g., engineers and hydrologists), city officials, federal government agencies, and other stakeholders as they seek to map flood risk while trying to achieve their diverse and conflicting goals (e.g., minimizing flood insurance costs while improving the accuracy of flood maps). Many important technological innovations are being developed to improve how we calculate flood risks, including, for instance, advances in real-time flood sensor systems, sophisticated hydrological models, and use of high-resolution satellite data. These innovations will fall short, however, if they don’t also address the non-technical and social aspects crucial to making knowledge systems work. In light of accelerated climate change and extreme coastal events, we suggest that more attention toward understanding flood risk as a knowledge systems problem can further advance resiliency goals for coastal cities.

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Acknowledgements

This material is based upon work supported by the National Science Foundation-funded Urban Resilience to Extreme Weather-Related Events Sustainability Research Network (UREx SRN; NSF grant no. SES 1444755), as well as dissertation research grants provided to Robert Hobbins from the Graduate Professional Student Association at Arizona State University and the American Association of Geographers. The authors are also very grateful for the time and information provided by practitioners in our case study cities and from the two anonymous reviewers who provided valuable feedback on earlier versions of this chapter.

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Hobbins, R., Muñoz-Erickson, T.A., Miller, C. (2021). Producing and Communicating Flood Risk: A Knowledge System Analysis of FEMA Flood Maps in New York City. In: Hamstead, Z.A., Iwaniec, D.M., McPhearson, T., Berbés-Blázquez, M., Cook, E.M., Muñoz-Erickson, T.A. (eds) Resilient Urban Futures. The Urban Book Series. Springer, Cham. https://doi.org/10.1007/978-3-030-63131-4_5

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Future Strategies

State Case Studies

Federal Review

Management Goals

Holistic Approach to Coastal FRM

CONTENTS ≡

CONTENTS ✕

Coastal Management Program

Shoreline regulations, floodplain management, wetland management, building codes, community planning, stormwater and runoff management, erosion management, climate adaptation initiatives, state management capacity, alternatives to structural mitigation, long-term planning, balance of mitigation and disaster recovery, holistic management approach, new york coastal flood risk management case study.

Policies and Programs

The New York Coastal Management Program , established in 1982, is housed within the New York Department of State’s Office of Planning, Development, and Community Infrastructure . Much of the program’s legislative authority is drawn from the state Waterfront Revitalization of Coastal Areas and Inland Waterways law as well as the Coastal Erosion Hazard Areas law . The program pursues goals related to coastal resources protection and development, local waterfront revitalization, coordination of major activities affecting coastal resources, public awareness of coastal issues, and federal consistency with state coastal management policies. Within New York, the Department of State administers the program and coordinates its implementation in cooperation with the state Department of Environmental Conservation as well as other state agencies.

Coastal program boundaries extend along the coast of Long Island, New York City, Hudson River estuary, both Great Lakes that border New York, and the Niagara River. Specific landward boundaries of the coastal program vary by region and locality due to initial delineation proposals from local government agencies. All barrier and coastal islands on Long Island are included within program boundaries along with areas 1,000 feet landward of the shoreline, extending further in some cases. The New York City program boundary generally extends 500 to 1,000 feet inland from the shoreline, with select areas along major tributaries also extending further. Within the Hudson River Valley the landward boundary is generally 1,000 feet but may extend up to 10,000 feet in areas that possess high aesthetic, agricultural, or recreational value. In the Great Lakes region the boundary is also generally 1,000 feet, though urbanized areas or transportation infrastructure parallel to shore limit the boundary to 500 feet or less in some cases.

Coastal management program consistency reviews require federal actions in the state coastal zone to be consistent with the enforceable policies of the state program or the policies of an approved local waterfront revitalization program. The program also contains provisions to ensure consistency of state actions in coastal areas. Of the 44 coastal management program enforceable policies in New York, seven specifically address flooding and erosion hazards. These policies touch on a number of aspects of coastal flood risk management including the siting of buildings in coastal areas to minimize risk to property and human lives, protection of natural features that mitigate coastal flood risk, construction of erosion control structures to to meet long-term needs, prevention of flood level increases due to coastal activities or development, prevention of coastal mining or dredging from interfering with natural coastal processes, use of public funds for erosion protection structures, and use of non-structural mitigation measures when possible. Additional enforceable policies address coastal development, fish and wildlife resources, public access, recreation, historic and scenic resources, agricultural lands, energy and ice management, water and air resources, and wetlands management.

At the state level, aspects of New York’s Environmental Conservation Law , Local Waterfront Revitalization Program , and State Environmental Quality Review permitting program influence coastal zoning and development decisions. Article 34 of the Environmental Conservation Law requires the identification of coastal erosion hazard areas and rates of recession of coastal lands. Shoreline setbacks must then be implemented at a distance that is sufficient to minimize damage from erosion. Article 36 of the Environmental Conservation Law , the state Flood Plain Management Act, also addresses coastal hazards, requiring walled and roofed buildings to be sited landward of mean high tide and prohibiting mobile homes within coastal high hazard areas, among other restrictions. Article 15, Water Resources Law , regulates the placement of coastal structures such as docks or piers and also addresses the placement of fill in coastal areas. Together these elements of the Environmental Conservation Law provide much of the legal basis for zoning decisions that can affect coastal flood risk at the municipal and local level.

Participation in the Local Waterfront Revitalization Program can also influence a local government’s coastal zoning decisions. In the process of preparing and adopting a revitalization program, local governments provide a more specific implementation of the state Coastal Management Program, taking advantage of local regulatory powers such as zoning ordinances and site plan review. Upon approval of a Local Waterfront Revitalization Program, state actions must then be consistent with the local program. In this way the enforceable policies of the Coastal Management Program, including those that relate to coastal flooding and erosion, are incorporated into local zoning decisions. Elements of enforceable policies are also incorporated into environmental permitting through the State Environmental Quality Review Program, which requires state agencies and local governments to prepare an environmental impact statement for any action that may have a significant impact on the environment. If an action in a coastal area requires the preparation of an impact statement, it must also be determined that the action is consistent with any relevant coastal enforceable policies. Consistency reviews must also be applied to NYS SEQRA type 1 actions as well as unlisted actions.

Floodplain management activities within New York are primarily conducted through the National Flood Insurance Program . Any regulations developed by the state must be at a minimum as strict as those prescribed by FEMA. Beyond the state level communities may adopt more restrictive floodplain management regulations. Within the state, local communities largely regulate development within federally designated Special Flood Hazard Areas, with state assistance provided by the New York State Department of Environmental Conservation. Local development permits govern private development within floodplains as well as development by a county, city, town, village, school district, or public improvement district, as specified in the state Environmental Conservation Law.

State standards for floodplain development permits in all designated special flood hazard areas require adequate anchorage and use of flood resistant material for all new construction and substantial improvement to existing structures. Utilities must also be designed in a manner that minimizes or eliminates risk of damage or failure during flood events. In areas where base flood elevation data exists, new construction or substantially improved residential structures must have the lowest floor at two feet above the BFE, including basements and cellars. Nonresidential structures may employ floodproofing to provide protection. Any enclosed areas below the base flood elevation must be designed to allow for the equalization of hydrostatic forces on exterior walls during a flood event. If no base flood elevation has been determined, new construction or substantially improved residential structures must be elevated above grade to the depth specified on the corresponding flood insurance rate map or two feet if no number is specified, with nonresidential structures again able to employ floodproofing measures. All state agency activities, whether directly undertaken, funded, or approved by an agency, must also be evaluated in terms of significant environmental impacts under the State Environmental Quality Review program, which includes a substantial increase in flooding as a criteria of significance. An environmental impact statement must be prepared if it is determined that an action may have a potential significant adverse impact.

All structures must be located landward of mean high tide levels within coastal high hazard areas, and all new construction or substantially improved structures must be elevated on pilings or columns so that the bottom of the lowest horizontal structural member of the lowest flood is elevated to or above the BFE. Pilings or column foundations must be adequately anchored, and fill is prohibited for use as a structural support for any new structure or substantial improvement. Space below the lowest floor may not contain obstructions to flood flows or otherwise be enclosed with non-breakaway walls. Any such space below the lowest structural floor may not be used for human habitation. New development or substantial improvement to structures must also not affect sand dunes in any way that increases potential flood damages.

The New York State Department of Environmental Conservation is also responsible for wetland management within the state. Statutory authority for wetland regulations stems from the Tidal Wetlands Act and Freshwater Wetlands Act , part of the larger state Environmental Conservation Law . Wetlands and wetland regulations are divided into either tidal or freshwater, and wetlands are further classified within each category. State wetland inventories containing information on delineated areas and classifications are made available for public use as part of the state wetland mapping program. Activities within wetland areas are regulated through a permit system.

Tidal wetlands regulations are designed to allow uses of wetlands that are compatible with the preservation, protection, and enhancement of ecological values including flood protection and storm control. Development restrictions require that all buildings and structures in excess of 100 square feet be located a minimum of 75 feet landward from tidal wetland edges, with less stringent setbacks in place for buildings located within New York City. Similar setback requirements exist for impervious surfaces exceeding 500 square feet. On-site sewage systems must have a setback of at least 100 feet, and a minimum of two feet of soil must be between the bottom of a system and the seasonal high groundwater level.

Permit standards for activities within tidal wetlands require that any proposed activity be compatible with the overall state policy of preserving and protecting tidal wetlands, and as such any activity may not cause any undue adverse impact on the ecological value of an affected wetland area or any adjoining areas. Standards also require that any activity within tidal wetlands be compatible with public health and welfare, be reasonable and necessary, and take into account both alternative actions and the necessity of water access or dependence for the proposed action. The state also publishes compatible use guidelines for activities within wetlands based on wetland type. If any activity is presumed to be incompatible with state tidal wetland use guidelines, an applicant must overcome the presumption of incompatible use and demonstrate that the activity is compatible with the preservation, protection, and enhancement of wetland values. If a use is specifically listed as incompatible within guidelines the use is then prohibited. Permitted activities in areas adjacent to tidal wetlands must also be compatible with public health and welfare, have no undue adverse impact on wetland ecological values, and comply with use guidelines.

State flood-resistant construction requirements are listed in the International Residential Code as adopted by New York State . Regulations apply to new residential buildings and structures located fully or partially within flood hazard areas as well as any substantially improved or restored structures within flood hazard areas. Construction requirements are based on the design flood elevation, which at a minimum must be the higher of either the peak elevation of a 1% annual chance flood event or the elevation of the design flood event as adopted on community flood hazard maps. Structures within flood hazard areas must generally be designed and anchored to resist the flood forces associated with the design flood elevation, and methods and practices to minimize flood damage must also be employed.

For the purposes of determining appropriate structural elevations, the lowest floor of a structure is defined as the lowest floor of any enclosed area, including basements. Within flood hazard areas not subject to high-velocity wave action, structures must have the lowest floor elevated to two feet above the base flood elevation or design flood elevation, whichever is higher. Utility systems must also be elevated to this standard. If no depth number is specified structures must be elevated not less than three feet above the highest adjacent grade. Any enclosed area below the design flood elevation must be used only for building access, parking, or storage and must contain flood openings sufficient to equalize hydrostatic forces on exterior walls.

For buildings and structures located in coastal high-hazard areas, including both V zones and Coastal A zones, the lowest floor must be elevated so that the lowest horizontal structural members are elevated to either the base flood elevation plus two feet or the design flood elevation, whichever is higher. Any walls below the design flood elevation must be designed to break away without causing damage to the elevated portion of the building, and again may be used only for parking, building access, or storage. Structures must be elevated using adequately anchored pilings or columns, with select exceptions in Coastal A zones. The use of fill for structural support and any construction of basement floors below grade are prohibited. New buildings and any substantially improved structures in coastal high-hazard areas must be located landward of the mean high tide, and any alteration of sand dunes must not result in any increased potential for flood damage in surrounding areas.

Planning at the state level is guided by the State Smart Growth Public Infrastructure Policy Act , an article within the larger Environmental Conservation Law. The act outlines criteria for public infrastructure projects that are either approved, directly undertaken, or financed by state infrastructure agencies. Among these criteria is a requirement that future public infrastructure projects mitigate future climate risk due to sea level rise, storm surge, or flood events based on available data or predictions of future extreme weather conditions. This and other criteria must be met to a practicable extent, and if deemed impracticable an agency must provide a detailed statement of justification.

The Office of Planning, Development, and Community Infrastructure within the Department of State administers several programs involved in community planning. The New York Rising Community Reconstruction Program provides recovery and resiliency planning assistance to communities affected by severe storm events, including hurricanes Sandy and Irene. The program is operated through the Governor’s Office of Storm Recovery and involves collaborations between state teams and community members to develop reconstruction plans and strategies to increase physical, economic, and social resilience, often including elements related to mitigating future flood risk. State Waterfront Revitalization Programs are also involved in community redevelopment planning. These programs establish land and water use policies and identify revitalization projects at a local level to allow for sustainable use of coastal resources, including planning for coastal flood risk resilience. Local Waterfront Revitalization Programs can also be a conduit for technical assistance and grant funding to facilitate climate change adaptation through the New York State Environmental Protection Fund grant program , a permanent fund addressing a broad range of environmental and community development needs.

The majority of stormwater regulations in New York focus on water quality issues as part of the State Pollutant Discharge Elimination System , a state program that has been approved by the EPA as part of the National Pollutant Discharge Elimination System . The program regulates point source discharges to both groundwater and surface waters and also conducts permitting for stormwater runoff from industrial activities, municipal sewer systems in urbanized areas, and construction activities. The program is administered by the state Department of Environmental Conservation.

While water quality is the focus of stormwater programs within the state, the state stormwater design manual lists best practices that include measures to reduce overbank flooding in order to maintain pre-development peak discharge rates for two and ten-year frequency storm events following development. The design manual also addresses risks due to potential floodplain expansion following development as well as green infrastructure strategies. These green infrastructure strategies are presented as a means to meet runoff reduction standards, which require that post-development conditions replicate pre-development hydrology. Stormwater projects, like all activities undertaken, funded, or approved by state agencies, are also under the purview of the State Environmental Quality Review Act , which requires preparation of an environmental impact statement if a project is likely to cause a significant increase in flood risk.

Coastal erosion in New York is managed within designated coastal erosion hazard areas. Areas are designated as per requirements of the state Coastal Erosion Hazard Areas Act , part of the larger state Environmental Conservation Law. Regulatory programs within identified hazard areas are administered by the state Department of Environmental Conservation. Programs may also be established at a local level if minimum state standards and criteria are met. The objectives of the program, as outlined in the state administrative code, are to ensure that activities in coastal areas subject to flooding minimize or prevent damage to property and natural features, that structures are placed at a safe distance from hazard areas to prevent premature damage to both structures and natural features, that public investment likely to encourage development within erosion hazard areas is restricted, and that publicly financed structures are only used when necessary and effective. Sections of the state administrative code also describe the erosion protection functions of natural protective features in order to guide the review of permit applications.

Coastal erosion management permits are required for any regulated activity conducted within a designated coastal erosion hazard area. Coastal erosion management permit standards require that any proposed activity be reasonable and necessary, with consideration of proposed alternatives, and that an activity will not likely lead to a measurable increase in erosion at the proposed site or other locations. Standards also require activities to prevent or minimize adverse effects to natural protective features, existing erosion protection structures, or natural resources such as fish and wildlife habitat.

Regulations within structural hazard areas allow for placement of movable structures, with construction restrictions, if a permit has been granted. Construction or placement of nonmovable structures is prohibited. Any public utility systems within structural hazard areas also require a coastal erosion management permit. Additional restrictions on regulated activities are present within natural protective feature areas, including nearshore areas, beaches, bluffs, primary dunes, and secondary dunes. Construction of erosion protection structures is allowed within such areas provided the structure meets permitting requirements and is designed to prevent or minimize damage to property and natural features in a cost-effective manner. Structures must be designed to control erosion on site for a minimum of 30 years.

New York has put forth several climate adaptation measures at the state level, led primarily by the state Department of Environmental Conservation. Sea-level rise projections for threatened coastal areas are currently published within the state administrative code, a recommendation from the previously convened NYS Sea Level Rise Task Force . The projections formally establish sea-level rise levels throughout Long Island, New York City, and the Hudson River, providing information based on five risk scenarios and extending out to 2100. The Department of Environmental Conservation has also formally acknowledged its role in climate change adaptation through Commissioner’s Policy 49: Climate Change and DEC Action . The policy outlines methods by which climate change considerations may be integrated into current DEC activities and programs, including making greenhouse gas reductions a primary goal, creating specific mitigation objectives for existing and future programs, incorporating adaptation strategies into programs and activities, considering climate change implications in daily department activities, and identifying specific actions to further climate change goals and objectives as part of annual planning processes. The policy goes on to establish mitigation and adaptation objectives as well as departmental responsibilities and implementation procedures.

The 2014 Community Risk and Resiliency Act (CRRA) forms the basis for a number of climate adaptation initiatives within New York from a legislative standpoint. The previously mentioned sea-level rise projections were a product of the CRRA, as the act amended the state Environmental Conservation Law to include a requirement that the DEC adopt science-based projections. The CRRA also amended additional sections of the Environmental Conservation Law to require applicants for identified funding and permitting programs to demonstrate that risk due to sea-level rise, storm surge, and flooding have been considered in project design and requires the DEC to incorporate similar considerations into facility-siting regulations. The sea-level rise, storm surge, and flood risk mitigation components of the Smart Growth Public Infrastructure Policy Act are also tied to the CRRA. The CRRA also directs the Department of State and Department of Conservation to develop model local laws that consider data-based future risk due to sea-level rise, storm surge, and flooding as well as guidance on the use of natural resources and natural processes to enhance community resilience to such hazards.

Elements of Policy Goals/Management Principles

State management capacity is bolstered by the New York Coastal Management Program’s federal consistency review process, which requires that federal activities within the state coastal zone be consistent with the program’s enforceable policies. The New York program has 44 enforceable policies in total, with 7 specifically addressing flood and erosion hazards.
Local governments can implement the state Coastal Management Program at a smaller scale through the Local Waterfront Revitalization Program, extending the influence of state program goals and enforceable policies.
The enforceable policies of the state coastal management program address the protection of natural features that mitigate coastal flood risk and the use of non-structural mitigation measures where feasible.
Shoreline setbacks must be established within identified coastal erosion hazard areas, and setbacks must be at a distance sufficient to minimize damage from erosion considering the rate of recession of coastal lands.
Floodplain management regulations require that any new development or substantial improvement to structures in coastal areas not affect sand dunes in any way that might increase potential flood damages.
Wetland management regulations require that structures be located a minimum of 75 feet landward from the edges of tidal wetlands, preserving natural flood risk mitigation functions.
Sections of the state administrative code related to erosion management include descriptions of the erosion protection functions of natural features to guide permit applications, and permit standards require that erosion management activities prevent or minimize adverse impacts on natural protective features.
The state stormwater management design manual includes information on green infrastructure strategies, which are presented as a means to meet runoff reduction standards and maintain pre-development hydrology for project areas.
The state building code requires structures not subject to wave action to have the lowest floor elevated a minimum of one foot above the base flood elevation. This rule applies to the lowest horizontal structural members of structures that are subject to wave action.
State regulations require that erosion protection structures in coastal areas be designed to control erosion on site for a minimum of 30 years.
Public infrastructure projects approved, undertaken, or financed by state agencies must account for and mitigate risk due to future climate risk factors such as sea-level rise, storm surge, and flood events. Mitigation efforts must be based on available data as well as projections of future conditions.
The state has published sea-level rise projections for threatened coastal areas within the state administrative code, formally establishing risk based on five scenarios and extending to 2100.
Commissioner’s Policy 49: Climate Change and DEC Action identifies ways that climate change considerations could be incorporated into current state programs and activities and defines departmental responsibilities and procedures for implementing the climate adaptation goals of the policy.
The state Community Risk and Resiliency Act formally establishes a number of climate adaptation initiatives within the state, including the requirement that the state Department of Environmental Conservation adopt science-based sea-level rise projections and that applicants to funding and permitting programs demonstrate that climate risk has been incorporated into the siting of facilities.
The enforceable policies of the state coastal management program address the siting of buildings in coastal areas to reduce risk and well as restrictions on the use of public funds for erosion protection structures.
One of the objectives of the state erosion management program as described in the state administrative code is to restrict public investment that could encourage development within coastal erosion hazard areas. An additional objective is to use publicly financed erosion control structures only when necessary and effective.
The New York Rising Community Reconstruction program works to develop reconstruction plans and strategies to increase coastal community resilience following severe storm events, often involving the mitigation of future flood risk.
The New York Coastal Management Program lists coordination of major activities affecting coastal resources as one of the program goals, and multiple state agencies are involved in implementing the program’s broad suite of enforceable policies.
If an action requires preparation of an environmental impact statement as part of the State Environmental Quality Review Program it must also be consistent with the enforceable policies of the state coastal program, including policies related to coastal hazards.
State wetland regulations are based on the preservation, protection, and enhancement of ecological values as opposed to acreage, with flood control and storm protection listed among the functions provided.
The State Environmental Quality Review Program includes the potential for a substantial increase in flooding as a criteria of significance, which then triggers the preparation on an environmental impact statement for state agency activities.
State Waterfront Revitalization Programs establish land and water use policies that incorporate coastal resilience into revitalization projects and community redevelopment planning.

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2020
2020, an experimental short course themed around the issue of flooding in York with representatives from York City Council, the Environment Agency and York Archaeological Trust. On a balmy afternoon at the end of June, an eagle-eyed observer might have spotted a band of suit-wearing students making their way across campus. This was a gaggle of ...
Producing and Communicating Flood Risk: A Knowledge System ...
5.2 New York City Flood Map Case Study. Our city needs precise flood maps that reflect real risks, both today and years from now, and we have to do that fairly—NYC Mayor Bill de Blasio ... After completing the Coastal Flood Study for New York in 2009, FEMA issued the 2015 Preliminary FIRM (P-FIRM) for NYC using new LiDAR data, more recent ...
New York Coastal Flood Risk Management Case Study
Article 36 of the Environmental Conservation Law, the state Flood Plain Management Act, also addresses coastal hazards, requiring walled and roofed buildings to be sited landward of mean high tide and prohibiting mobile homes within coastal high hazard areas, among other restrictions.
A Community Works Together to Reduce Damages from Flooding
The Village of Walton, New York worked with their Soil and Water Conservation District to engage community members in decisions about flooding in their community. The Village eventually took action to restore portions of the floodplain to reduce flooding. Case Studies A Community Works Together to Reduce Damages from Flooding
york flooding case study
In 800 claims, at an average of £25,000 per flooded property. The flooding also cost the City of York Council £1.3m with protecting properties by sandbags and other means was the biggest single expense, at £394,000. Over £100,000 was paid to the fire service, and £41,000 to the army for the help they provided.... Flood York 2015: Anatomy of a Flood Disaster York has known devastating ...