Tag Archives: building on London floodplain

Another development on Thames floodplain

A new suburb the “size of Windsor” is being planned for Barking Riverside, the site of the old Barking Power station, according to a report in the Financial Times.

barking riverside
The Barking Riverside site is sandwiched between two sewage works and a power station

Some 10,800 homes are being planned for the 179-hectare site by the housing association London & Quadrant in association with the Greater London Authority. The report states that £70m will be invested in extending the London Overground rail line to the site. But no mention is made on how much will be invested in flood defences.

Nor does it say that the site is sandwiched between sewage works on either side of the river and a power station and the Ford Motor works to the east.

It is part of the Mayor of London’s ambition for a City in the East that also makes no mention of how much money will be invested in flood defences to make these new estates safe.

This 200,000 home masterplan for East London should be music to the ears of anyone struggling to find a place to live in our overcrowded capital.

But unless planners are willing to spend billions on new flood defences it is possible that these new homes will be particularly at risk of flooding should rainfall levels increase with climate change.

The Environment Agency's Flood Plan map of the Thames illustrates Howard's comment that "the Thames was so full during this time that no tide was perceptible"
The Environment Agency’s Flood Plan map of the Thames illustrates Howard’s comment that “the Thames was so full during this time that no tide was perceptible”

Many of the developments mooted in London Mayor Boris Johnson’s plan for a City in the East are situated on flood plain, according to the Environment Agency.

On reading through the blueprint flood risk isn’t mentioned once.

A report in the Financial Times, citing the plan, says there is much more potential than previously thought to increase housebuilding in east London, the capital’s planning chief estimates. Sites earmarked include the Lea Valley and areas along the Thames beyond Canary Wharf.
‘Thames Riverside’, the term for an area along the north side of the Thames including Barking and Beckton, could host 27,000 homes, while areas on the opposite side of the river could hold 22,000, according to the report. There could be 52,000 more homes in Lea Valley, 30,000 on the Isle of Dogs and 15,000 in Woolwich.
Sir Edward Lister, deputy mayor for policy and planning, believes the capital’s authorities had learned from their experience with the Nine Elms regeneration area, where a statement of intent had galvanised developers.
“We just have to commit and then the developers can move in,” adding that there were “vast” amounts of underused post-industrial sites along the river in east London.
The housing plans also include commercial and industrial buildings, giving potential to create 280,000 jobs, as well as supporting infrastructure such as schools and hospitals. Transport improvements, such as Crossrail and a new London Overground line, would make the developments ‘desirable’. But costs would be dwarfed by any flood defence improvements.
Previously the Environment Agency has outlined a range of options for the future of the Thames Estuary flood defences. None are particularly cheap.

As a minimum, the EA estimates that the cost of maintaining the defences until 2035 will be around £1.5 billion, with an additional £1.8 billion needed to repair and upgrade the defences until 2050. Particular bits of marshland could also be set aside to store tide waters.

The River Lea close to where Luke Howard's laboratory stood by wanstead_meteo
The River Lea close to where Luke Howard’s laboratory stood

More ambitiously, the government could fund a new barrier in either Tilbury in Essex or Long Reach in Kent. Such a barrier would be designed to resist the highest surge tides identified by the Met Office’s analysis of how conditions will change this century. The EA estimates a new barrier could cost as much as £7 billion, though that figure could go up if conditions change significantly as the climate changes.

The Agency also say the existing barrier could be converted to include locks, which could open and close more flexibly and extend the life of the defences. The EA report says a decision on a new barrier will have to be made by 2050.

It may turn out that there’s a more pressing reason to spend. The EA says 50 is the maximum number of times the barrier should close each year, and beyond that, the barrier could start to fail.

How high is the likelihood of flooding in this part of London? A look back through history shows the geography of the Lea Valley has made the area prone to inundations for hundreds of years.

The Environment Agency's Flood Map for Planning shows the flood zone risk of the area. And endorses Howard's account that the river Lea was 'a mile wide' at its peak
The Environment Agency’s Flood Map for Planning shows the flood zone risk of the area. And endorses Howard’s account that the river Lea was ‘a mile wide’ at its peak

In January 1809 the lower River Lea burst its banks in several places following a deluge that dumped two inches of rain in the space of 24 hours. The rain abruptly ended a snowy cold spell that had begun over a month before in the middle of December. From Luke Howard’sreadings it is likely that up to half a metre of snow had fallen in the previous weeks in the upper parts of the surrounding countryside with only slight thawing. With the frozen ground unable to absorb any of the rapidly melting snow and rainfall the amount of water flowing downstream must have been immense. Howard takes up the story…

“The River Lea continued rising the whole of the 26th… The various channels by which it intersects this part of the country were united in one current above a mile in width which flowed with great impetuosity and did much damage.”

Howard, his chemical factory located on the banks of the river Lea close to what is now Bow flyover, wrote at length about the event, his account replacing the usual brief notes about daily weather in his book The Climate of London.

He talks of embanked pasture land being “filled to the depth of eight or nine feet” and people driven to their upper rooms relieved by boats plying under the windows.

“The Thames was so full during this time that no tide was perceptible.” It took until February 23rd for things to return to normal.

Wanstead Flats by Scott Whitehead
Wanstead Flats during the wet winter of 2013-14

Miraculously no lives were lost in the flood and cattle “by great exertions” were saved by being kept in their stalls. Howard, saying that the flood could have been far worse, believed a neap tide, strong westerly winds urging water down the Thames and mild weather helped avert a tragedy.

Howard’s statistics of the previous months show that the second half of 1808 were wetter than average – though not especially so. And nothing like the rainfall this area recorded during the winter of 2013/14. From December 1st until February 8th 1809 Howard recorded 130mm of rain, which is about 100mm less than what was recorded during 2013/14.

This fact alone shows just how much the nature of the river has changed in the last 200-odd years thanks to spending on flood defences.

Work to improve the defences was prompted 67 years ago when similar catastrophic flooding came with the thaw that ended the severe winter of 1947, one of the coldest winters in history and an episode remarkably similar to what Howard recorded in 1809.

The Lea Valley, along with many parts of the country, saw some of its worst flooding in a generation. The river burst its banks at several points bringing misery to surrounding communities. Valleys turned into lakes in 40 counties and East Anglia’s fens were a sandbagged inland sea. More than 100,000 properties were damaged and, then as now, heroic battles were fought by the military to keep water-pumping plants and power stations dry.

A marker of that flood, together with a history of flood defences, can be found here. There is also British Pathe footage of another flood between 1910 and 1919 here .

mill
Spillers Millennium Mill was repainted 25 years ago especially for the concert. It now provides the backdrop for the London Triathlon across from the ExCeL centre

The River Lea Flood Relief Channel, that flows between Ware, Herts, and Stratford, took almost three decades to complete. The channel incorporates existing watercourses, lakes and new channels. Since it was completed in 1976, there have been no major flood events in the Lea Valley, although there have been three occasions when the river system was full virtually to its capacity: in 1987, 1993 and 2000. Since its completion, the level of protection afforded by the structure has declined, so that in some areas it offers 2 per cent protection, and in some, only 5 per cent protection. The EA published a strategic environmental assessment in 2008, which looked at ways to maintain the flood defences in the Lea Valley.

In summing up its ambitions for a new development the Greater London Authority says it is trying to “overturn the historic perception of the east being seen as apart from London, rather than as a part of London”.

Jim Ward, a director of research at property consultancy Savills, said the challenge was “building something that makes people want to live and work there”, he said. “You need to build more than homes, you need to build a place.”

Boris’s record of late has not been good: an estuary airport to replace Heathrow has been dismissed as pie in the sky while his promise for a 24-hour Tube was made without first consulting unions that it was possible.

London’s safety from flooding is an altogether different proposition, both for old and new developments. Boris really needs to get London’s flood defences right before any brick is laid on these desperately-needed new developments.

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Greenwich Peninsula awash with development

The race to build more riverside property on London’s floodplain has received another boost after a big development on the Greenwich Peninsula was given the green light.

The Environment Agency's Flood Plan map of the Thames illustrates Howard's comment that "the Thames was so full during this time that no tide was perceptible"
The Environment Agency’s Flood Plan map of the Thames

The Financial Times reported on Friday that Boris Johnson has given final approval to an £8.4bn, 12,700-home development that would transform this area of south-east London into a “high-rise urban village complete with film studio”.

Knight Dragon have already begun construction on the project, a 150-acre scheme approved 10 years ago in a more modest form but revived and expanded after the financial crisis.

The report mentions that local residents are concerned the scheme will place unbearable strain on the area’s transport links and that the size and density is out of keeping with Greenwich’s World Heritage Site of 17th to 19th-century buildings close by.

What is not mentioned is flood risk – a factor that, considering climate models, is deemed too minuscule to worry about. The proposed development satisfies this risk criteria – a report on the ‘Strategic Flood Risk Assessment’, drawn up in October 2011, mentions:

“Tidal flood risk is extensive, but at present Greenwich is fully defended against the 0.1% annual probability extreme tide level with climate change to 2107. A breach in the defences, although a low probability of occurrence, would have a high consequence, causing significant flooding of the Thamesmead, New Charlton and Greenwich Peninsula areas of the Borough.”

But is it wise to build on historic floodplain? Surely we should be looking elsewhere in London for safer sites for projects that will help ease the housing crisis.

The website floodlondon.com shares concern that developments such as these are at severe risk from a tidal surge when the Thames Flood Barrier nears the end of its working life in the middle of this century.

“Perched on the very tip of the Greenwich Peninsula, the O2 Arena finds itself ideally located on a nice sharp bend in the river where it is likely to take the full brunt of the surge as it careers into the bank, much like a racing car taking a corner too fast. The North Greenwich tube station just across the road will prove to be a great asset at this point as it funnels the water into the Jubilee Line.”

Before the Thames Barrier was built this part of the river has seen some catastrophic flooding.

thames flood november 18 1875
The 1875 flood as reported in the Morning Post
In November 1875, a year that was only slightly wetter than normal, a record high tide of 8.9m was recorded at Blackwall. The figure is 1.36m (4ft 6in) higher than the greatest high tide at North Woolwich (Silvertown) this year, according to tide tables drawn up by the Port of London Authority (7.54m on March 20th).
The flood brought chaos throughout London – with this part of the river particularly badly hit. Much of the Isle of Dogs was inundated, North Woolwich Gardens were under 3ft (1m) of water while the water caused explosions at the Royal Arsenal. Elsewhere in the capital Eton College was ‘completely surrounded by water’. A correspondent for the Press Association said the damage caused on the banks of the Thames was estimated to cost £1m sterling – just over £103m at today’s prices.
tues 16 nov
The Sunderland Daily Echo & Shipping Gazette on Tuesday, November 16, 1875 reported a depth of water at East India Docks of 29ft 2in. Damage was estimated to be £1m sterling – just over £103m at today’s prices.

Since the flood of 1953 measures, including the Thames Barrier, were put in place to stop this flooding. The Environment Agency has outlined a range of options for the future of the Thames Estuary flood defences. None are particularly cheap. As a minimum, the EA estimates that the cost of maintaining the defences until 2035 will be around £1.5 billion, with an additional £1.8 billion needed to repair and upgrade the defences until 2050. Particular bits of marshland could also be set aside to store tide waters.

The EA estimates a new barrier could cost as much as £7 billion, though that figure could go up if conditions change significantly as the climate changes.

Greenwich Peninsula and another project, City in the East, which was announced last month will need proper flood protection and planning. I wonder if planners are as willing to invest in these defences as they are at making a tidy buck developing these riverside schemes. And do our politicians have the appetite to drive the legislation through?

The problem is that if the climate change does bring greater rainfall and an unprecedented sea-level rise it is the people living in these properties that will be faced with the problem of ever-increasing costs to fight off the risk of inundation.