The effects of tall buildings on their surroundings go far beyond their visual impact, a remarkable symbol of modern architecture and engineering.
Altering wind patterns is one of the most significant ways high-rise buildings impact the natural world.
Discover what happens to winds and tornadoes when tall buildings are present:
1. Create Wind Tunnels
If you live or work near tall buildings, you might have noticed that the wind can be much stronger in certain areas.
That’s because the buildings can create a tunnel that makes the wind speed up and become concentrated. This can make some areas much windier and more dangerous, especially for people walking or cycling.
Several things contribute to creating these wind tunnels, such as:
- The Height
- The Shape
- The Direction and Speed of the Wind
- The Surrounding Area’s Features
Wind tunnels can make localized wind speeds much higher than normal. Additionally, wind tunnels are a big concern in cities with tall buildings.
Architects can design buildings with shapes that reduce wind resistance and turbulence to improve things. They can also widen the spaces between buildings to allow wind to flow more easily and add canopies and windbreaks to slow down the wind.
By doing this, they can create a safer and more comfortable environment in urban areas with tall buildings.
2. Cause Wind Shear
Knowing about wind shear is crucial if you live or work in a high-rise building.
Wind shear happens when the wind changes speed or direction rapidly over a small distance. Tall buildings can cause wind shear by interrupting wind flow and creating different wind patterns at different heights.
The lower part of the building can slow down the wind, while the upper part can speed it up. This can cause significant turbulence, making it difficult for planes to take off or land safely.
Wind shear can also be dangerous for people on the ground, as it can cause objects to be blown around or knocked over.
The effect can be particularly hazardous in urban areas with tall buildings.
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3. Increase Wind Speed at Higher Levels
Tall buildings can impact wind patterns and increase wind speeds at higher levels.
This occurs because the building obstructs the airflow, creating high pressure on the windward side and low pressure on the leeward side. As a result, wind speeds can increase over the top of the building.
Furthermore, if the building is not designed to withstand strong winds, the facade could be damaged, or the structure could be compromised.
High winds also increase the risk to people on the ground from debris blown around. For instance, signs, trash cans, and construction materials can become dangerous projectiles and cause extensive harm to nearby people and property.
The risks associated with higher wind speeds due to high-rise buildings must be mitigated. Engineers and architects can use wind-absorbing or wind-resistant materials to fortify buildings against the elements.
Materials like reinforced concrete and wind-resistant glass can make buildings more resistant to strong winds.
4. Deflect Wind
Tall buildings can cause the wind to deflect around them, creating swirling air currents that can affect nearby buildings.
This can be a significant issue in densely populated urban areas, where buildings are often close together. The turbulence generated by tall buildings can make it challenging to accurately predict wind speed and direction.
When wind deflects around tall buildings, it can create areas of low pressure on the leeward side of the building. This can cause the wind to swirl around the building, creating a turbulent and unpredictable airflow.
5. Alter the Course of Tornadoes
High-rise buildings can significantly impact tornadoes.
Tornadoes are extremely destructive, violently spinning columns of air that can cause widespread destruction. The impact of tall buildings on tornadoes can be complex and depends on several factors, including the building’s height, shape, and location.
The presence of tall buildings can significantly alter the path of a tornado or even cause it to lose strength. When a tornado encounters a tall building, it can be deflected, changing its path and potentially reducing its strength.
However, this can also lead to multiple tornadoes as the deflected air creates new vortexes.
Furthermore, the location of tall buildings in urban areas can affect the formation and strength of tornadoes. Urban areas with tall buildings can experience more significant disruptions to the surrounding wind patterns, which can either enhance or weaken tornadoes.
This can create a more unpredictable and potentially dangerous situation, particularly in densely populated areas.
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6. Impact Tornado Formation
Tall buildings in cities worsen the urban heat island effect, which causes cities to be warmer than their surroundings.
As tall buildings tend to have more surface area, they absorb and retain more heat. The heat generated by tall buildings can also impact local weather patterns, leading to changes in wind patterns and atmospheric conditions.
These changes in weather patterns can potentially impact tornado formation. Tornadoes require specific atmospheric conditions to form, including warm and humid air near the ground and cooler air at higher elevations.
The urban heat island effect can create warmer air temperatures, potentially disrupting the atmospheric conditions required for tornado formation.
7. Act as Windbreaks
Tall buildings can act as windbreaks by creating a barrier that slows down and redirects the wind flow.
When the wind meets a tall building, it generates eddies and turbulence that slow down the wind and cause low-pressure areas on the building’s leeward side.
The combination of decreased wind velocity and a low-pressure area can make the area behind the building relatively wind-free.
This protected space can provide shelter from strong winds, making it ideal for pedestrians, outdoor activities, and building occupants, especially during extreme weather events such as storms and hurricanes.
Moreover, tall buildings can also help to mitigate wind damage to nearby buildings, trees, and other infrastructure. When high winds occur, tall buildings act as a barrier that slows down and redirects the wind flow, breaking up and diffusing the wind.
This reduces its intensity and can lessen the damage it causes.
Reducing the Effects of Tall Buildings on Wind and Tornadoes:
To reduce the impact of wind and tornadoes on tall buildings, architects and engineers have developed various strategies.
One approach is to use tapered building shapes, which can minimize the effects of wind by reducing the formation of vortices and eddies.
Another option is to install windbreaks and screens that deflect wind away from the building, reducing the impact of wind on the structure.
However, the most effective way to mitigate the effects of tornadoes on tall buildings is to design them to be tornado-resistant. This involves using strong and flexible materials and designing the building to withstand the strong winds and debris that tornadoes can bring.
Including safe rooms or shelters within the building can also help protect occupants during a tornado.
Urban planning considerations are also crucial in mitigating the effects of tall buildings on wind and tornadoes. Placing tall buildings in areas that are less prone to tornadoes can help reduce the risk of damage.
Additionally, ensuring that buildings are not placed too close together can help prevent wind tunnel effects and the formation of vortices.
WHYY – The Science of Wind Tunnels – Where and Why Those Harsh Winds Strike
Structville – Vortex Shedding and Wind Load Analysis of Tall Buildings
JLC Online – Wind-Resilient Buildings