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March 2020

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Aremi MacDonald

Remembering Bridgewater: How one U.K. city taught us a lesson in wind safety

Today, March 10th marks a day of reflection for the city of Leeds - and for architects, urban designers and real estate developers all over the world (we hope).

Bridgewater Place remains the tallest building in the city, and one with tragic history. How did Leeds’ first skyscraper, intended as a symbol of modern and forward architecture earn the title the “Killer Tower” of Yorkshire?

The 110-metre-high tower was responsible for creating terrible microclimate conditions at street-level due to an adverse wind effect known as Downwash. Bridgewater Place received overwhelming criticism. Pedestrians were constantly being blown away, and windy conditions in the city kept getting worse and worse.

It was evident that inaccurate wind analysis had been undertaken when designing the tower. This mistake was costly in more ways than one, but the biggest consequence of it all resulted in a fatality. On March 10, 2011, a 35-year-old-man was killed when a lorry was blown over in the city centre around the base of the tower and injured nearby pedestrians in its wake.

Two years later, Leeds City Council enforced strict road closures around Bridgewater Place whenever the forecast predicted high winds. During these road closures, pedestrians to this day are still diverted to walk behind windscreens along alternate routes around the building to ensure their safety. 

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Bridgewater’s owners agreed to pay £903,000 to cover the public money spent towards the cost of building wind deflection structures, constructing screens, canopies and baffle boards (shown above) to mitigate the wind at street-level.

 

 

A lesson learned is a lesson earned in wind mitigation

The urbanisation of our skylines is here to stay, which is why proactively planning for the wind is essential to the safety of pedestrians and bicyclists in the city. As we’ve learned with Bridgewater Place, trying to mitigate wind effects in the late construction stage – or after the structure is completed for that matter – is expensive and not always efficient.

To shine a light into possible design optimisations, here are some techniques architects and urban planners use to avoid uncomfortable winds at street-level:

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CANOPY: The overhead roof goes beyond giving shelter against rain or sun, it also migrates the adverse effect of wind on pedestrians.

 

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SETBACK: Changes of sectional shapes modify the flow pattern around the construction, therefore airflow is improved at street-level and around the building. 

 

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GRADUAL HEIGHT TRANSITION: Limiting drastic height transitions from one building to the other helps increase pedestrian comfort.

Wind microclimate: best considered when considered early

The Bridgewater case is an extreme example of how things can turn from bad to worse when naturally strong winds encounter poorly designed urban areas. And with that extreme example, we learn that assessing wind behaviour in the early stages of designing a building benefits everyone across the board.

1. It helps architects and urban designers maintain control of the design process, eliminating the risk of re-working project proposals.

2. Saves taxpayers and municipalities money spent trying to retroactively find solutions to the consequences chalked up to poor urban planning. Once a building is constructed, it really is too late.

3. And most importantly ensures the safety and comfort of pedestrians and bicyclists in the city. If anything, Bridgewater has taught us that quality urban wind analysis could save a life!