In the introductionary blogpost about agroforestry, a few options have been mentioned as possibilities for mixing trees, crops and animals. One of those options was planting trees as a wind barrier. This blogpost is looking into that. How can trees and hedges provide good protection against wind? And what are the gains from a wind barrier?
The advantages of wind barriers
Wind barriers can have a lot of advantages. The FAO has compiled quite a few of the advantages of a wind barrier:
- They protect the (vulnerable) crops and trees behind the barrier
- They reduce evaporation of plants
- They reduce open water evaporation, so that more water is available for other uses
- They protect plants against very high or very cold temperatures of the wind
- They make it possible to stabilise dunes (just like dune grasses)
- They can protect the crops behind the barrier against salt spray from the sea
- They improve pollination by insects (less easily blown away). Also, the wind barrier protects the insects against very high or very low temperatures of the wind.
- They can reduce the spread of diseases, but because the wind barrier reduces drying out, the increased moisture levels, can also result in increase number of diseased plants
- They reduce the change that physiological changes in plants happen due to strong winds
But you have to realise that these benefits only occur when the windbreak is designed well!
Designing starts with understanding the system
As explained in the previous blog, the design of a regenerative system starts with a good understanding of the system. This system understanding is also necessary for the design of a wind barrier. From which direction comes the wind that you want to stop, and from which direction comes the wind that you want to use; this can be especially the case if the wind coming from a certain direction can be used to cool, and it has to be directed to a specific location (for example with a layered design of shrubs and trees, or with two parallel lines of trees that become a very narrow alleyway).
A wind barrier also gives shade and filters noise. When performing a system analysis, it is therefore also useful to immediately include the shadow (keep in mind that the shadow direction depends on whether you are in the northern or southern hemisphere) and any noise to be filtered out.
In order to choose the right vegetation it is important to know how strong the wind is that has to be stopped. This can be measured directly, but it is also possible to use vegetation in the area: the more asymmetrical these have grown, the stronger the wind. The Griggs Putnam Energy index has been developed for this, see the figure below.
Finally, it is important to know during which period of the year you want to block something (sound, wind or sun). If the plants and trees are without leaves, the barrier effect is a lot different than in full leaf. So if you want to block noise 12 months a year, maybe conifers are better compared to plants that loose their leaves in the autumn.
Effectiveness of wind barriers
1. Multiple layers or one layer
Some wind barriers are designed as a narrow dense high hedge, but it can also be done differently. How it is designed ultimately depends on the amount of space and the functions that are given to the wind barrier.
In addition, it may be the case that you want to use the wind from a certain direction, for example to cool a house, or to block the wind. The figure below shows how the positioning of trees and shrubs can be used to direct the wind where you want to use the wind (requires proper maintenance).
2. The density of the wind barrier
As is the case with all gases or liquids flowing around hard edges: there is turbulence when there is flow around a very hard edge. If the barrier is very closed, it is therefore a hard barrier to the wind and turbulence occurs behind the hedge (downwind). However, if the barrier is not too dense, and some of the wind can flow through the hedge, a large part of the turbulence (which affects the crops) is prevented.
The twitter feed below shows the impact a single tree can have.
3. The thickness and height of the wind barrier in relation to the influence distance
How far the zone of influence of the wind barrier extends differs somewhat per study. This source gives an influence zone of about 10 times the height. Another book gives a zone of influence (viewed from the ground) of a dense hedge of 5 to 10 times the height, roughly 5 (bandwidth 4 to 5.12) times the height of the hedge far, with the windward side of the hedge as 0-point has been taken (source appendix 8 from this book). A thin or a very thick hedge (thickness of the hedge up to 2 times the height of the hedge) was also considered. The zone of influence from the 0-point remains reasonably the same. A very thick hedge therefore gives less space for other crops and plants. From an efficiency point of view, a narrow hedge that is as high as possible is therefore very useful. However, if the hedge is also used for other purposes, the thickness of the hedge becomes less important. With a porous hedge, the zone of influence extends further as the porosity increases, up to 15 times the height; with increasing porosity, the wind speed behind the wind barrier remains higher compared to a closed hedge (see first figure below). However, different studies show different graphs, which is why the figures from 2 studies are shown.
The two figures both show that there is a clear reduction in wind speed as a result of a wind barrier. The reduction, especially with more porous screens, seems to differ and the reach of the barrier, this is clearly visible at 15 H, where all lines in the top figure are around 80%, while those in the bottom figure are between 80 and 90%. Factors such as screen roughness, definition of openness and number of measuring points during the trial and how high above ground level is measured can all influence the results. In any case, it is clear that a reduction of the wind speed to 20 to 40% of the original wind speed is easily attainable, with very dense barriers this can increase to 60 to 80% of the original wind speed.
\At the same time, it appears that the speed (certainly with dense wind barriers) can increase in certain places well above the ground. The figure below shows that with a wind barrier that is 15% open, the wind speed just above the wind barrier at a short distance from the wind barrier can increase quite a bit, (the air is compressed to flow over the barrier and the flow speed of the air increases just above the barrier), but also directly behind the barrier nearly at the ground.
It should be noted that if the wind blows at an angle on the wind barrier, the "protected zone" is reduced, because in that case the 5 to 10 times the height is measured under an angle and therefore reaches less far into the field.
4. influence on evaporation and precipitation
In order to determine the influence of the wind on evaporation, the resistance in the stomata of plants is examined (the "stomatal resistance", rs). The resistance is lower with a better moisture supply; the drier it is, the higher the resistance becomes. If sufficient moisture is present (low resistance), evaporation increases at higher wind speeds; with little available moisture (high resistance), evaporation decreases at higher wind speeds.
The influence of a wind barrier is in the opposite direction, the wind speed decreases. In wet conditions evaporation will therefore decrease, while in dry conditions it can increase and thus cause a stronger local cooling of the air, while this local microclimate is not blown away.
An additional factor to this is the resistance of the landscape (aerodynamic resistance), which is "defined the other way around" and expressed in s/m. A smooth surface (bare soil) has a high value and a rough surface (forest) has a low value. In the graph below, the resistance of the landscape is plotted against the resistance of the stomata.
In this graph the line is plotted whereby evaporation remains the same with an increase in wind speed. Above this line (the white part) the evaporation decreases with decreasing wind, at the bottom right (the gray part) the evaporation increases with decreasing wind.
A wind barrier with crops will be somewhere between crop and forest; in slightly drier conditions the evaporation can then increase (slightly) compared to an unprotected monoculture.
One effect that can be "exploited" is the fact that the barrier formed by the trees compresses the air above the trees. This compression can result in reaching a water vapour concentration in the air such that condensation of water can occur. The wind barrier can therefore provide extra local precipitation behind the wind barrier. However, it may also be the case that the extra precipitation at wind barriers results in less precipitation further downwind (source), in case the total precipitation remains the same.
5. impact on the harvest
In general, a wind barrier seems to lead to an increase in yield of up to 40%. It should be noted here that the yield decreases locally, due to competition with the wind barrier plants in particular. The effect of the windbreak on the yield can reach up to 20 times the height of the barrier (source).
The increase is caused by several factors: the plant is no more/less damaged/torn, or shaken by the wind. Sandblasting with sediment and dust also occurs less frequently. In addition, fewer diseases will pass by. And finally, it is much better to maintain a microclimate around the plant. This can be more humid, but can also be warmer soil and air temperature (source).
In Russian studies it has been found that there is a difference in yield increase when applying wind barriers between dry and wet years. The increase in yield was up to 150 to 300% increase in dry years, while the increase in wet years was 10 to 30%. In addition to increases found in potatoes, grains (corn, wheat), beets, apples, strawberries, lettuce and sugar beets, conflicting (decrease and increase) or no results have also been found in barley, wheat, rye and oats (source).
In addition to an increase in yield, a change in the microclimate can improve the quality of the product. The moment fruit development can also take place earlier.
As the Russian study showed, the impact of a wind barrier strongly depends on the meteorological conditions in the different years studied. The graphs below show yields behind a wind-shield for apples and pears. The apples were examined from 1952 to 1958, the pears only from 1956 to 1958. In 1956 and 1957 the impact of a wind barrier is very large, because the harvest far from the screen for the pears is 60 to 70%. lower. The yield of apples is 20 to 30% lower. In 1953 the influence of the wind barrier is actually not present, the fluctuation in yield is so limited that it can also be attributed to other factors. Pears therefore seem to be more sensitive to wind compared to apples. A mutual wind barrier distance of 6H to 10H is therefore recommended for apples, while 2H to 4H is recommended for pears.
Research on strawberries mainly showed earlier fruiting of sheltered plants, at 2H of the wind barrier strawberries could be picked, while at 8H this was only available a week later (see figure 15 of this report). The yield was also higher between 2H and 6H than with the rest.
With potatoes, the shelter from the wind resulted in a much earlier but also better development of the plant. More nodules are formed in the plants close to the wind barrier. Later in the season, however, the potatoes of the plants with fewer tubers are larger. The differences in the number of kilograms of potatoes per plant are therefore smaller during the harvest.
Similar results were also found for lettuce and carrots. Lettuce grows better under sheltered conditions and can therefore be harvested earlier. The number of plants is higher with the carrots, so germination seems to be going better, and ultimately both the foliage weight and the root weight are greater.
Design guidelines and tips and trics (source)
When designing regenerative systems, the permaculture adage applies: make sure that everything has at least 3 functions, so that you create a strongly intertwined ecosystem.
For the wind barrier, the question is what functions are given to it in addition to stopping the wind:
However, when choosing planting, the following should be taken into account:
The design based on the local conditions is crucial for the proper functioning of the wind barrier: which wind should be stopped, which might be used correctly, how strong is this wind, how is shade created, what are the soil conditions and how wet/dry is it, etc.
In order to create a wind barrier that becomes a closely interwoven ecosystem, it is important to consider what additional functions should be given to the barrier. Is it used for biodiversity, mulch material, nitrogen fixation, fruits, nuts? All these functions together determine how the wind barrier can be designed.
The wind barrier affects the wind speed on the ground up to about 15 to 20 times the height of the wind barrier. In this zone the influence on the local wind velocity can be observed.
The influence of the wind barrier on plants is first of all on plant development, in the shelter seed germinates better, plants develop earlier, are less damaged, all of which contribute to a higher yield.
In short, a very useful addition for regenerative agriculture!
- https://www.agroforestry.org/the-overstory/141-overstory-129-windbreak-design
- https://www.agroforestry.org/the-overstory/232-overstory-32-multipurpose-windbreaks
- http://www.fao.org/3/T0178E/T0178E03.htm/
- http://www.fao.org/3/x0490e/x0490e06.htm
- http://www.fao.org/docrep/T0178E/T0178E03.htm
- http://www.fao.org/docrep/T0178E/T0178E05.gif
- https://www.ccmaknowledgebase.vic.gov.au/resources/Bird_et_al_1992.pdf
- https://www.yourhome.gov.au/passive-design/passive-cooling
- https://www.harvestingrainwater.com/product/rainwater-harvesting-for-drylands-and-beyond-volume-1-3rd-edition-new-2019/
- https://www.harvestingrainwater.com/wind-snow-harvesting/
- https://www.researchgate.net/publication/225897050_Windbreak_Aerodynamics_Is_Computational_Fluid_Dynamics_Reliable
- https://www.researchgate.net/publication/226203416_Effects_of_windbreaks_on_airflow_microclimates_and_crop_yields
- https://www.researchgate.net/publication/332251720_Design_of_Tall_Cable-Supported_Windbreak_Panels
- http://article.sapub.org/10.5923.j.ije.20160601.02.html
- https://earthscience.stackexchange.com/questions/2454/why-is-aerodynamic-resistance-defined-inversely
- https://treeyopermacultureedu.com/chapter-6-trees/windbreaks/
- https://www.fs.usda.gov/nac/practices/windbreaks.php
- https://upower.weebly.com/griggs-putnam-energy-index.html
- https://edepot.wur.nl/182142
- https://library.wur.nl/WebQuery/wda/104550
The advantages of wind barriers
Wind barriers can have a lot of advantages. The FAO has compiled quite a few of the advantages of a wind barrier:- They protect the (vulnerable) crops and trees behind the barrier
- They reduce evaporation of plants
- They reduce open water evaporation, so that more water is available for other uses
- They protect plants against very high or very cold temperatures of the wind
- They make it possible to stabilise dunes (just like dune grasses)
- They can protect the crops behind the barrier against salt spray from the sea
- They improve pollination by insects (less easily blown away). Also, the wind barrier protects the insects against very high or very low temperatures of the wind.
- They can reduce the spread of diseases, but because the wind barrier reduces drying out, the increased moisture levels, can also result in increase number of diseased plants
- They reduce the change that physiological changes in plants happen due to strong winds
But you have to realise that these benefits only occur when the windbreak is designed well!
Designing starts with understanding the system
As explained in the previous blog, the design of a regenerative system starts with a good understanding of the system. This system understanding is also necessary for the design of a wind barrier. From which direction comes the wind that you want to stop, and from which direction comes the wind that you want to use; this can be especially the case if the wind coming from a certain direction can be used to cool, and it has to be directed to a specific location (for example with a layered design of shrubs and trees, or with two parallel lines of trees that become a very narrow alleyway).
|
| Source: https://www.yourhome.gov.au/passive-design/passive-cooling |
A wind barrier also gives shade and filters noise. When performing a system analysis, it is therefore also useful to immediately include the shadow (keep in mind that the shadow direction depends on whether you are in the northern or southern hemisphere) and any noise to be filtered out.
|
| Source: https://treeyopermacultureedu.com/chapter-6-trees/windbreaks/ |
In order to choose the right vegetation it is important to know how strong the wind is that has to be stopped. This can be measured directly, but it is also possible to use vegetation in the area: the more asymmetrical these have grown, the stronger the wind. The Griggs Putnam Energy index has been developed for this, see the figure below.
|
| Source: https://upower.weebly.com/griggs-putnam-energy-index.html |
Finally, it is important to know during which period of the year you want to block something (sound, wind or sun). If the plants and trees are without leaves, the barrier effect is a lot different than in full leaf. So if you want to block noise 12 months a year, maybe conifers are better compared to plants that loose their leaves in the autumn.
Effectiveness of wind barriers
1. Multiple layers or one layerSome wind barriers are designed as a narrow dense high hedge, but it can also be done differently. How it is designed ultimately depends on the amount of space and the functions that are given to the wind barrier.
In addition, it may be the case that you want to use the wind from a certain direction, for example to cool a house, or to block the wind. The figure below shows how the positioning of trees and shrubs can be used to direct the wind where you want to use the wind (requires proper maintenance).
2. The density of the wind barrier
As is the case with all gases or liquids flowing around hard edges: there is turbulence when there is flow around a very hard edge. If the barrier is very closed, it is therefore a hard barrier to the wind and turbulence occurs behind the hedge (downwind). However, if the barrier is not too dense, and some of the wind can flow through the hedge, a large part of the turbulence (which affects the crops) is prevented.
|
| Source: http://www.worldagroforestry.org/Units/Library/Books/Book%2006/html/8.9_trees_as_wind.htm?n=90 |
The twitter feed below shows the impact a single tree can have.
Another field about 2.5kms away. North is at the top of the image pic.twitter.com/8NkSkO37Xl
— Evan MacDonald (@emacdonaldag) September 1, 2021
3. The thickness and height of the wind barrier in relation to the influence distance
How far the zone of influence of the wind barrier extends differs somewhat per study. This source gives an influence zone of about 10 times the height. Another book gives a zone of influence (viewed from the ground) of a dense hedge of 5 to 10 times the height, roughly 5 (bandwidth 4 to 5.12) times the height of the hedge far, with the windward side of the hedge as 0-point has been taken (source appendix 8 from this book). A thin or a very thick hedge (thickness of the hedge up to 2 times the height of the hedge) was also considered. The zone of influence from the 0-point remains reasonably the same. A very thick hedge therefore gives less space for other crops and plants. From an efficiency point of view, a narrow hedge that is as high as possible is therefore very useful. However, if the hedge is also used for other purposes, the thickness of the hedge becomes less important. With a porous hedge, the zone of influence extends further as the porosity increases, up to 15 times the height; with increasing porosity, the wind speed behind the wind barrier remains higher compared to a closed hedge (see first figure below). However, different studies show different graphs, which is why the figures from 2 studies are shown.
|
| Source: https://www.researchgate.net/publication/226203416_Effects_of_windbreaks_on_airflow_microclimates_and_crop_yields |
|
| Source: https://edepot.wur.nl/182142 |
The two figures both show that there is a clear reduction in wind speed as a result of a wind barrier. The reduction, especially with more porous screens, seems to differ and the reach of the barrier, this is clearly visible at 15 H, where all lines in the top figure are around 80%, while those in the bottom figure are between 80 and 90%. Factors such as screen roughness, definition of openness and number of measuring points during the trial and how high above ground level is measured can all influence the results. In any case, it is clear that a reduction of the wind speed to 20 to 40% of the original wind speed is easily attainable, with very dense barriers this can increase to 60 to 80% of the original wind speed.
\At the same time, it appears that the speed (certainly with dense wind barriers) can increase in certain places well above the ground. The figure below shows that with a wind barrier that is 15% open, the wind speed just above the wind barrier at a short distance from the wind barrier can increase quite a bit, (the air is compressed to flow over the barrier and the flow speed of the air increases just above the barrier), but also directly behind the barrier nearly at the ground.
|
| Source: https://www.researchgate.net/publication/226203416_Effects_of_windbreaks_on_airflow_microclimates_and_crop_yields |
It should be noted that if the wind blows at an angle on the wind barrier, the "protected zone" is reduced, because in that case the 5 to 10 times the height is measured under an angle and therefore reaches less far into the field.
4. influence on evaporation and precipitation
In order to determine the influence of the wind on evaporation, the resistance in the stomata of plants is examined (the "stomatal resistance", rs). The resistance is lower with a better moisture supply; the drier it is, the higher the resistance becomes. If sufficient moisture is present (low resistance), evaporation increases at higher wind speeds; with little available moisture (high resistance), evaporation decreases at higher wind speeds.
The influence of a wind barrier is in the opposite direction, the wind speed decreases. In wet conditions evaporation will therefore decrease, while in dry conditions it can increase and thus cause a stronger local cooling of the air, while this local microclimate is not blown away.
|
| Source: https://www.researchgate.net/publication/226203416_Effects_of_windbreaks_on_airflow_microclimates_and_crop_yields |
An additional factor to this is the resistance of the landscape (aerodynamic resistance), which is "defined the other way around" and expressed in s/m. A smooth surface (bare soil) has a high value and a rough surface (forest) has a low value. In the graph below, the resistance of the landscape is plotted against the resistance of the stomata.
In this graph the line is plotted whereby evaporation remains the same with an increase in wind speed. Above this line (the white part) the evaporation decreases with decreasing wind, at the bottom right (the gray part) the evaporation increases with decreasing wind.
A wind barrier with crops will be somewhere between crop and forest; in slightly drier conditions the evaporation can then increase (slightly) compared to an unprotected monoculture.
|
| Source: https://www.researchgate.net/publication/226203416_Effects_of_windbreaks_on_airflow_microclimates_and_crop_yields |
One effect that can be "exploited" is the fact that the barrier formed by the trees compresses the air above the trees. This compression can result in reaching a water vapour concentration in the air such that condensation of water can occur. The wind barrier can therefore provide extra local precipitation behind the wind barrier. However, it may also be the case that the extra precipitation at wind barriers results in less precipitation further downwind (source), in case the total precipitation remains the same.
5. impact on the harvest
In general, a wind barrier seems to lead to an increase in yield of up to 40%. It should be noted here that the yield decreases locally, due to competition with the wind barrier plants in particular. The effect of the windbreak on the yield can reach up to 20 times the height of the barrier (source).
|
| Source: http://www.fao.org/3/T0178E/T0178E03.htm/ http://www.fao.org/docrep/T0178E/T0178E05.gif |
The increase is caused by several factors: the plant is no more/less damaged/torn, or shaken by the wind. Sandblasting with sediment and dust also occurs less frequently. In addition, fewer diseases will pass by. And finally, it is much better to maintain a microclimate around the plant. This can be more humid, but can also be warmer soil and air temperature (source).
In Russian studies it has been found that there is a difference in yield increase when applying wind barriers between dry and wet years. The increase in yield was up to 150 to 300% increase in dry years, while the increase in wet years was 10 to 30%. In addition to increases found in potatoes, grains (corn, wheat), beets, apples, strawberries, lettuce and sugar beets, conflicting (decrease and increase) or no results have also been found in barley, wheat, rye and oats (source).
In addition to an increase in yield, a change in the microclimate can improve the quality of the product. The moment fruit development can also take place earlier.
As the Russian study showed, the impact of a wind barrier strongly depends on the meteorological conditions in the different years studied. The graphs below show yields behind a wind-shield for apples and pears. The apples were examined from 1952 to 1958, the pears only from 1956 to 1958. In 1956 and 1957 the impact of a wind barrier is very large, because the harvest far from the screen for the pears is 60 to 70%. lower. The yield of apples is 20 to 30% lower. In 1953 the influence of the wind barrier is actually not present, the fluctuation in yield is so limited that it can also be attributed to other factors. Pears therefore seem to be more sensitive to wind compared to apples. A mutual wind barrier distance of 6H to 10H is therefore recommended for apples, while 2H to 4H is recommended for pears.
|
| Source: https://edepot.wur.nl/182142 |
|
| Source: https://edepot.wur.nl/182142 |
Research on strawberries mainly showed earlier fruiting of sheltered plants, at 2H of the wind barrier strawberries could be picked, while at 8H this was only available a week later (see figure 15 of this report). The yield was also higher between 2H and 6H than with the rest.
With potatoes, the shelter from the wind resulted in a much earlier but also better development of the plant. More nodules are formed in the plants close to the wind barrier. Later in the season, however, the potatoes of the plants with fewer tubers are larger. The differences in the number of kilograms of potatoes per plant are therefore smaller during the harvest.
Similar results were also found for lettuce and carrots. Lettuce grows better under sheltered conditions and can therefore be harvested earlier. The number of plants is higher with the carrots, so germination seems to be going better, and ultimately both the foliage weight and the root weight are greater.
Design guidelines and tips and trics (source)
When designing regenerative systems, the permaculture adage applies: make sure that everything has at least 3 functions, so that you create a strongly intertwined ecosystem.For the wind barrier, the question is what functions are given to it in addition to stopping the wind:
- Will it be a habitat for all kinds of wildlife (affects breadth and maintenance)?
- Are nitrogen fixers used?
- Is this used to grow fruits and nuts?
- etc.
However, when choosing planting, the following should be taken into account:
- Factor number 1 is: can the vegetation - used for the wind barrier - withstand the wind and does it grow well on the soil present there. Because if the vegetation is not healthy, does not function well, then there is no good wind barrier.
- In case of multiple functions performed by the wind break: it may also be the case that the wind barrier becomes wider, in order to allow the production in the wind barrier to function optimally. It is then important that it consists of different types. The different species protect each other (for example at different heights), but this also means that a (tree) species must be pruned, the other species still function well as a wind barrier. Finally, a diverse system is more resistant to diseases and pests.
- If a habitat is chosen for all kinds of wild animals:
- the longer the wind barrier the better, and make sure it is connected at the beginning and end to something else (e.g. a bush) so that it can become a corridor for wildlife
- provide various flowers and other fruits to attract insects
- make it as diverse and layered as possible to make the ecosystem as diverse but above all as strong as possible
- cover the soil with wood, branches and leaves for habitat
- If you choose to produce fruit or nuts in the windbreak:
- make sure that flowering takes place in the months with less wind (if the winds are seasonal)
- plant these in the more sheltered parts of the wind barrier
- see if you can choose varieties that bear fruit on the main branches instead of the outer branches
- as these are most upwind, evaporation may be higher, which may require additional irrigation here.
Conclusion
Wind barriers have largely disappeared in the Dutch landscape where large-scale industrial agriculture takes place. These come into play again when switching to a more regenerative polyculture.The design based on the local conditions is crucial for the proper functioning of the wind barrier: which wind should be stopped, which might be used correctly, how strong is this wind, how is shade created, what are the soil conditions and how wet/dry is it, etc.
In order to create a wind barrier that becomes a closely interwoven ecosystem, it is important to consider what additional functions should be given to the barrier. Is it used for biodiversity, mulch material, nitrogen fixation, fruits, nuts? All these functions together determine how the wind barrier can be designed.
The wind barrier affects the wind speed on the ground up to about 15 to 20 times the height of the wind barrier. In this zone the influence on the local wind velocity can be observed.
The influence of the wind barrier on plants is first of all on plant development, in the shelter seed germinates better, plants develop earlier, are less damaged, all of which contribute to a higher yield.
|
In short, a very useful addition for regenerative agriculture!
Sources:
- http://agrilife.org/etg/2014/12/22/solving-wind-sound-visual-problems-with-plants/- https://www.agroforestry.org/the-overstory/141-overstory-129-windbreak-design
- https://www.agroforestry.org/the-overstory/232-overstory-32-multipurpose-windbreaks
- http://www.fao.org/3/T0178E/T0178E03.htm/
- http://www.fao.org/3/x0490e/x0490e06.htm
- http://www.fao.org/docrep/T0178E/T0178E03.htm
- http://www.fao.org/docrep/T0178E/T0178E05.gif
- https://www.ccmaknowledgebase.vic.gov.au/resources/Bird_et_al_1992.pdf
- https://www.yourhome.gov.au/passive-design/passive-cooling
- https://www.harvestingrainwater.com/product/rainwater-harvesting-for-drylands-and-beyond-volume-1-3rd-edition-new-2019/
- https://www.harvestingrainwater.com/wind-snow-harvesting/
- https://www.researchgate.net/publication/225897050_Windbreak_Aerodynamics_Is_Computational_Fluid_Dynamics_Reliable
- https://www.researchgate.net/publication/226203416_Effects_of_windbreaks_on_airflow_microclimates_and_crop_yields
- https://www.researchgate.net/publication/332251720_Design_of_Tall_Cable-Supported_Windbreak_Panels
- http://article.sapub.org/10.5923.j.ije.20160601.02.html
- https://earthscience.stackexchange.com/questions/2454/why-is-aerodynamic-resistance-defined-inversely
- https://treeyopermacultureedu.com/chapter-6-trees/windbreaks/
- https://www.fs.usda.gov/nac/practices/windbreaks.php
- https://upower.weebly.com/griggs-putnam-energy-index.html
- https://edepot.wur.nl/182142
- https://library.wur.nl/WebQuery/wda/104550
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