The Urban Wind, Impact Assessment – Letter to Boris

sent in by a local resident

“I attach here, a copy of an email that was sent to the Mayor of London

Dear Sir,

I am a resident in Vauxhall and have recently been researching an issue that raises concern.

Having some knowledge and living experience, of the change in conditions that tall structures can bring to a vicinity, I have been wondering if there has been an assessment of the overall influence on wind conditions that may occur, downwind of the cluster of proposed tall buildings in and around the Vauxhall one way system, or gyratory, as it is also known.

When wind conditions are mild, there should no consequence. However, when we experience the seasonal gales that are known to bring down roof tiles, break thick branches of trees, or even bring down street signage, I am concerned that the overall effect of the cluster of tall buildings that is proposed for Vauxhall, may reach far enough to have an effect on the KiaOval Cricket ground, an internationally renowned sporting venue.

The KiaOval Cricket ground is located in a direction, directly downwind of the tall buildings cluster, when the strong westerly winds blow and is located at a distance of a mere 500-to-700 meters away, from the nearest proposed tall building, that of 30-60 South Lambeth Road.  Playing conditions at the venue, could be dramatcaly altered, by turbulence and gusts or swirling wind, or the grandstands may not have been designed to withstand the newly introduced wind conditions, for example.

Existing housing and buildings within the downwind zone, could potentially experience a change in wind conditions such that roof damage may become a frequent occurrence, or windows may be blown out of their frames. Also, personal injury could result from such falling materials.

The point being, that there appears to be no evidence that this issue of overall wind effect, has ever been considered since thus far, I have been unable to find any report or assessment, of the impact on wind conditions in the area located downwind of a cluster of tall buildings.  The science has been around for a decade, at least. It is known that the cumulative effect of a cluster of tall buildings, may be more than that of the individual buildings, during strong wind conditions, or that the interaction of structures determines the resulting conditions.

Here, I stand to be corrected, in my perception that, for the accuracy of simulation or modelling to be improved upon, or the margin of error, to be refined and reduced to a minimum, the regulations should require that actual wind speed measurements are obtained over a period of all four seasons, for a duration of one year at least. Using wind speed data that has been measured at remote sites, does not include any local effect on the wind, prior to it reaching any proposed site of a development.

Actual wind speed measurements should be taken from any proposed sites for talll buildings and from various locations within the areas that are downwind from the location of the proposed building. Accurate, real wind speed measurements should take place at multiple sites within the downwind area of any planning applications for the purposes of the simulation and trials in the wind tunnel. Furthermore, after completion of construction, a verification of the simulation results should occur. The changes in wind conditions should be measured again at the same locations, in order to correlate and correct for any margin of error that is inherent in simulation models.

The present planning application requirements require a Wind Assessment report and rightly so, however, the limitation thereof, is that the terms of these assessments are confined to the loadings upon the structure itself and the effect on pedestrian comfort, only within the immediate vicinity of the building location, nothing more.  The wind effect of tall buildings and more so, clusters of tall buildings, should be given a priority equal to that of the protection of the visual impact of a tall building or the protection of heritage views.

With regard to the quality of input data for the simulations, I am concerned, that by excluding durations less than one hour and by averaging wind speed data, the true, peak, wind speeds of gusts during gales, are not represented. A margin of error is therefore, inherent in the results and conclusions of a Wind Assessment.  The reports I have read in this regard, have not specified the margin of error, or degree of confidence in the results

A few queries follow:

1. I would appreciate receiving any information regarding which authority should be responsible for the assessment of the wind effect on an entire area that forms part of an urban strategic policy, for developments such as the cluster of tall buildings proposed in Vauxhall.

2. If any research into this particular area has been commissioned, I would be delighted to hear.

3. Does a Wind Assessment report exist, for the overalll scope of the cluster of tall buildings, as proposed for Vauxhall by the VNEB OAPF policy/plan?

I hope to receive information that will go some way towards allaying the concerns I have.

Sincerely,

Brian Vos”

Since Brian’s letter (to which the Mayor did not reply) the following articles (see links below) regarding unexpected wind speeds since the building of Bridgwater Place (110 m) in Leeds have come to our attention:

http://www.bbc.co.uk/news/uk-england-leeds-12717762

http://www.bbc.co.uk/news/uk-england-leeds-16968325 

Also see related article on the Vauxhall Society website:

 http://www.vauxhallcivicsociety.org.uk/2012/02/damage-can-skyscraper-air-turbulence/

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