Eolian Mapping
Many parameters influence the amount of wind erosion that occurs, however, several are critical and can be considered major factors in the eolian process. Two of these critical parameters are the percent of vegetation cover and the type of surface soils. Using satellite digital multi- spectral data a simple model has been developed that allows an image to be generated that emphasizes areas with low vegetation density and high reflectance soils. Generally, this automatically maps two of the important eolian erosion paramters (i.e., amount of vegetation cover/ density and general surface soil type). An image product is generated using this model that shows areas where these two conditions occur simultaneously. In this image product, various shades of yellow indicate different levels of low vegetation density and high reflectance soils, and serve as a guide to the relative level of erosion potential/ vulnerability to wind. These can be used to generate an Eolian Mapping Index (EMI) value at each pixel. In the Landsat MSS image products shown below the brighter yellows have a higher erosion potential than the more dull yellows, with the non-yellows having little or no wind erosion potential.
Click on each of these images to see larger versions (1000K, 786K, 1095K)
Northern Arizona MSS | 
Yuma, Arizona MSS | 
Wyoming MSS |
The image results shown above are for the Northern Arizona (left image), Yuma, Arizona (middle image), and Wyoming (right image) test sites. Again, the brighter yellows have a higher eolian erosion potential than do the more dull yellows, and the non-yellow areas have little, if any, eolian erosion potential.
Part of the current analysis and field work are related to evaluating the accuracy of the digital EMI image. Several sites in Northern Arizona that show transitions between eolian and non-eolian materials, or between eolian and vegetated eolian materials are being studied to:
- Determine the ability of the eolian algorithm to resolve sharp transitions.
- Determine in a quantitative way whether or not surface material is vulnerable to eolian erosion. This is done using a 500-micron sieve to measure the first 1 cm of the soil to compute the percentage of 500 micron or less material. Particles with less than 500 micron diameter are readily eroded by the wind, therefore, this gives an approximate measure of its eolian composition and related eolian vulnerability. These data will be correlated with the various eolian erosion image products being generated using the Landsat MSS and TM images.
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