Modifying Wind for Cool Season Landscape Design Purposes

As wind moves through your landscape, it is modified by buildings, tree canopies and other solid and porous objects.  In cool season wind areas, the greater the difference in temperature between the air and the object, the greater the cooling effect and in winter when the temperature difference between a person and the air is at a maximum, modifying wind can reduce “windchill”.  This means that landscape designs for areas to be used in cool seasons, such as an outdoor living area, should focus on reducing wind speed by creating a wind block.

Of all the elements in a landscape to characterize and control through design, both biologically and physically, wind is probably the most difficult to control through design, however there are a few standard approaches that can help modify winds in your landscape design.  Once you have determined your cool season prevailing winds, orient your outdoor space away from these prevailing cool season winds and provide upwind barriers perpendicular to prevailing cool season winds.  A good example is to install a coniferous windbreak that deflects your cool season or winter winds.  By selecting the porosity of the object to utilize in your wind modification, you can control the amount of wind reduction and size of area, commonly referred to wind reflection zone.  Trees with 50 percent porosity that are low branched to the ground will reduce wind speed greater and create a wider wind reflection zone than open branched deciduous trees and conifers whose branches don’t reach to the ground.  As water will continue to flow after it encounters an obstruction, so will wind and will flow over and around.  Through design of properly placed vegetation, this wind can be reduced further or channeled to flow through areas that would benefit from increased winds. 

When modifying wind through proper design principles, we can also modify solar radiation to provide beneficial microclimates, a landscape that has been designed to modify both the wind and solar radiation to provide a thermally comfortable place for people.  In the upcoming blog we will discuss strategic modification of solar radiation and the benefits of active and solar heating, survival of plants and habitat for animals.  It will contain information on landscape design utilizing proper landscape vegetation that can modify and increase poor air quality in urban settings.  

Resources:  Brown, Robert D., and Terry J. Gillespie

Microclimatic Landscape Design:  Creating Thermal Comfort and Energy Efficiency

John Wiley and Sons, Inc.

Ponds to Water features- Design through Implementation (2nd of a 2 Part Series)

Once location and size of your water feature has been determined, water movement and flow rate calculations are necessary.  As mentioned in the first part of this series, creating “live” water is essential for the proper maintenance of your feature and to create oxygen in the water to support aquatic and plant life.  The simplest design is to create a ledge or rill through which water flows (supported by a pump) back into a lower basin.  The higher the vertical lift (bottom of pond to top of rill or ledge), the larger the flow rated pump should be.  A good reference is a that a 4,800 gph flow rated submersible pump utilizing a 1.5” diameter return line creates great flow rates and sound for a vertical lift of 48” – 54”.  Always remember submersible pumps are all about water flow, not pressure, so it is important to maximize return line size in accordance with your pump’s flow rate.

Under natural conditions, ponds are part of an eco-system that contains a marsh area filled with reeds and sedges.  This is a good strategy to incorporate in your pond construction and should be part of your overflow system.  Designing an overflow that infiltrates this marsh area will be perfect in the wetter months, supporting these types of plants, and then allowing the marsh area to dry out in the less precipitation months.  This natural condition is vital for the proper growing cycle for plants that like “wet feet”.  Some of the plants that are capable of growing in wetland conditions include astilbe, gunnera, iris sibirica, and trollus to name a few.  Many plants flourish in these conditions with the elimination of competition from vigorous plants such as equisetum and algae.  Amphibians such as frogs and toads will enjoy these seasonally dry marshes as their fish predators will not be able to prey on their tadpoles.

Properly managing your plants in and around your water feature is easily accomplished by understanding and matching the conditions in which they grow naturally.  These matrices are supported by the proper soils and wet meadows occur in heavy loams consisting of clay and silt, and occasionally peat.  It is important to study these natural environments and recreate them forming a dense and permanent plant cover to reduce weed growth that can be tenacious in these environments.

If you are considering or dealing with a bank, the point where static water meets land, rapid stabilization of the bank to resist erosion is important.  Some very good soil-binding plants include acorus, athyrium, dryopteris, rodgersia and spartina.

Shallow waters are home to numerous plants which can help stabilize the waters edge as they spread slightly into the moist soils where water meets land.  These plants have exploratory root systems and this readiness to produce new roots enables them to spread easily throughout a water system, creating a fast growing upperstory essential for the aquatic life below while creating a balanced and healthy pond.  Many of these marginal plants are intolerant of frost and will need to be protected during the winter months and can be accomplished by covering them or simply removing them and storing until the following season.  Calla, juncus, peltandra, and hydrocharis are some good choices for smaller sized ponds. 

There is an unlimited way to create ponds or water features in regards to shape and style, but the dynamics are consistently the same.  Creating live water supported by proper flow rates, water movement and depth along with proper vegetation selections will support a successful, easily maintained and sustainable water feature.