Wind Patterns at Landfills

At a landfill, you have to deal with winds of different speeds and strength, steady winds, gusting winds, and winds that come from different directions.   The topography of your site affects the wind patterns at your site.  Know and understanding these winds and wind patterns is key to understanding how to properly apply your litter controls. 



Wind Over The Ground

Wind that blows over the ground creates a micro-pattern along the ground surface.  As the wind passes over the ground, the wind speed is slowed due to friction with the ground surface.  The type of vegetation and surface roughness will influence the degree of this effect.  For the most part, you would not notice this effect.

What is important to understand, is that smaller particles and easily airborne particles will stay suspended in the air.  Heavier particles will tend to flow across the ground until they are trapped by and object.

This can be seen by observing the materials that makes up the litter at different distances from the landfill operation.    

Wind Over Hills

Hills cause a variety of effects on wind as it passes over.  As the wind blows into the hill, it will tend to decrease in speed at the toe of the hill.  This is because a high pressure zone occurs on the windward side of the hill.  As the air mass moves up the hill slope, it will accelerate and will reach a maximum speed at the apex of the hill.   A low pressure zone will occur on the downwind side of the hill and a reduced wind speed may be observed.  

Turbulent winds may also show on the upwind and downwind sides of the hill depending on wind speed and the shape of the hill.  

In a landfill setting, these wind patters can be observed around stockpiles and fill areas.   Dust can be observed drifting off the crest of a soil stockpile and litter can often be observed circulating in the turbulent winds on the downwind side of stockpiles and fill slopes.   

Wind Funneling

In a geographic valley setting,  such as a mountain pass, wind that blows through the valley can accelerate.   The valley acts like a venturi tube.  As wind enters the valley it is compressed and increases in speed.  When the wind exits the valley, the air pressure decreases, but the exiting wind is at a much higher speed than when it entered the valley.   (look up Santa Anna Wind)

This same funneling effect can occur in a landfill setting where the wind is blowing parallel to an narrow open trench, or where it blows between two fill areas.  The effect of this funneling may not be easily observed as it's effect may be minimal in most cases. 

Topographic Exposure

The diagram at left shows an example topographic setting with perpendicular winds and parallel winds.  A active fill area with the greatest exposure to strong winds are shown red, while low exposure is shown in green.   A landfill operator should know where the highest topographical exposure area is at the landfill.  It will not be the same for all landfills and all wind situations. 

Observe the Wind

To develop an effective landfill litter management plan, the landfill manager should observe wind patterns on and around the landfill.  Observe winds around all topographical features, both mounds and open excavations.   Observe wind patters at different wind directions and speeds.   Measure the winds.  You can purchase hand held wind meters that you can use as you walk through the site.  Record the different wind speeds. 

Observe turbulent air patterns.  You can often see plastic film circulating in turbulent air.  You may also notice the wind speed recorded on your hand held wind meter is very erratic in highly turbulent air. 

Observe how the wind effects your active working face and tip area.  How is the litter wind blown, and where it goes to.   Take photographs and record what you observe. 

Understanding Global Winds

For a landfill operator to become insightful towards effective litter control, he needs to pay attention to and understand wind patterns around the landfill.  But, we'll start with explaining a few basics about global wind patterns.

The wind patterns around the earth has something to do with the coriolis effect, which has to do with the rotation of the earth. In most of North America, global winds are generally blowing from west to east, and most of our weather systems move west to east.  Think of which direction most of our summer storms come from.

In tropical climates, the trade winds are generally blowing towards the east.   Weather systems in the tropics tend to move from east to west.  Think of the direction that hurricanes and cyclones move around the globe.  



Regional wind patterns are influenced by high and low pressure zones.  The air moves in circular patterns around these pressure areas.   Winds will blow clockwise around high pressure zones, and counter clockwise around low pressure zones.   The direction of the wind where you are depends on where you sit within these high and low pressure areas. 

Understanding these basic wind patterns can be useful in planning the layout of a landfill development with consideration of prevailing winds, and by paying attention to local and regional weather systems, the operator can adjust daily operations and litter controls according to weather forecasts. 

Much of this information can be obtained from local weather stations.  In Canada, you can go online and log on to Environment Canada and get up to date weather information. 

In forthcoming posts, I will discuss regional wind patterns that are influenced by geography.