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Satellite images can
be used to develop
an index which maps
the severity of
wind erosion |
Severe winds can cause erosion on susceptible areas of farming land,
particularly during the summer months when there is less vegetative ground cover. Wind
erosion causes the loss of valuable top soil; nitrogen-rich dust can be blown into the
ocean and lost forever.
Satellite data can be used to map wind erosion, to calculate the area affected by wind
erosion, and to record how quickly wind-eroded areas recover. Calibrated sequences of
images, taken over a number of years, can be analysed to develop an index which indicates
the degree of wind erosion.
The index can be applied to produce a map showing areas affected by wind erosion in
each year. The effect of changes in farm management practices can be easily monitored. By
combining wind erosion maps over different years, areas which are susceptible to wind
erosion can be identified.
This information can then be used to modify farming practices or design interventions
in these areas. In time, information about past wind erosion events can be used to
forecast areas at risk during the summer.
Case Study
The South Stirlings area has suffered several wind erosion events in the last decade.
It is believed that changes in farming practice have led to less susceptibility to
erosion. The impact of these changes can be assessed using sequences of carefully
calibrated satellite images.
In early 1988, large areas of the South Stirlings were affected by wind erosion. In the
enhanced Landsat TM image below right, the white areas have been wind-blown.
| Eroded areas which are irregular in shape, particularly those which align with the
erosive wind direction (in this case, NW to SE), are probably highly erodible soils such
as sand dunes. Those eroded areas which are regular in shape reflect management within
individual paddocks. Adjoining paddocks which received the same wind conditions may not
have blown because of better management of the soil surface (such as more vegetative cover
and / or less disturbed soil). |
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Using a sequence of calibrated images, an index was developed which indicates the
degree of wind erosion. This is illustrated in the image at left. The wind erosion index
can be applied to the images in the sequence, to produce maps showing wind-eroded areas
for each year. |
By overlaying the wind erosion maps for each year, a map showing areas of frequent
erosion can be produced (see opposite). This map indicates areas that appear most
susceptible to wind erosion, and for which different farming practices may need to be
applied.
Areas susceptible to wind erosion - green shows areas that have suffered one wind
erosion event in 1988-1993, yellow areas have suffered two wind erosion events and red
areas have suffered three or more wind erosion events. |
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