Download Wind erosion intensity determination by airbone capture

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WIND EROSION INTENSITY DETERMINATION BY AIRBONE
CAPTURE
Lenka LACKÓOVÁ, Tomáš URBAN1
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Slovak University of Agriculture, Faculty of Horticulture and Landscape Engineering,
Department of Landscape Planning and Ground Design
ABSTRACT
The airborne capture method determines the intensity of wind erosion using soil particle
catchers which trap soil particles transported by the wind at different heights above the
soil surface in the specific conditions affecting the occurrence, process and intensity of
wind erosion. For soil particle capture in the field we designed the first prototype of soil
particle catcher. In the field measurements we tried to trap the moving soil particles, due
to wind, through the first prototype soil particle catcher.The duration of each measurement
was always 60 minutes. The calculation of the quantity of particles captured per unit area
is very simple because the width of the entrance is 5 cm. Multiplying the width and length
of erosive surface in the wind direction we can calculate the area of wind erosion
surface.The results of the wind erosion events analysis show that during the monitored
period effective erosive winds lasted a total of 58 hours. The most frequent average hourly
wind speed ranged from 5.0 to 5.9 ms-1 and the period of occurrence lasted a total of 28
hours. The maximum average minute wind speed reached 12.3 ms-1 and a maximum gust
of wind was 17.3 ms-1.
Key words: airboone capture, soil particle, wind erosion
INTRODUCTION
Soil degradation due to erosion is the irreversible loss of the surface, the most fertile layer of
soil; loss of humus, organic matter, nutrients, reduction in soil biological activity and the
overall deterioration of the natural processes in land use and crop production as well as
decrease in production capacity in the affected soil (Demo et al. 2000). .If a longperiodof
droughtoccurs at this time and is followed by a period ofeitherintenseprecipitation(water
erosion) orhigh intensitywinds(winderosion) erosion will occur (Halva, Dudek, 2003). The
process of wind erosion (aeolian) is via the loss of the soil surface by mechanical wind forces
(abrasion), moving and transporting the soil particles (aggregates) by wind (deflation) and
depositing them elsewhere (accumulation). Wind erosion is a physical phenomenon and it is
directly influenced by the physical properties of the soil, by kinetic energy, and by many
other factors (Stre8anský, 1993). The potential vulnerability of the agricultural soils of
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Slovakia was calculated by the Research Institute for Soil Science and Conservation,
Bratislava. About 3.2% of agricultural land is subject to high or extreme vulnerability to wind
erosion. Despite the small size, the effects are significant, so it is necessary to geographically
locate the most affected area and suggest erosion measures (Muchová, Vanek, 2009). The
process of wind erosion causes damage to agricultural land especially erosion of soil
particles, fertilizers, seeds and pesticides. It exposes plant roots and eroded soil particle
damage young plant shoots in particular. (Pokrývková, Kalúz, 2012).the resultantamount
ofsoilerosionisaccurately determinedgeographically (Kliment, Kliment, 2012).
MATERIAL AND METHODS
The airborne capture method determines the intensity of wind erosion using soil particle
catchers which trap soil particles transported by the wind at different heights above the soil
surface in the specific conditions affecting the occurrence, process and intensity of wind
erosion. For soil particle capture in the field we designed the first prototype of soil particle
catcher (fig. 1). The apparatus consists of a tapered entrance through which the circulating air
flows into the body of the soil particle catcher, which absorbs the kinetic energy of wind.
Inside the soil particle catcher are the three filters that trap the soil particles. The entrance
section consists of a hole, which is 5 cm wide and 20 cm high. The narrow input section
gradually expands and connects to the body of the contraption, which is 25 cm wide and 20
cm high. The soil particle catcher is 130 cm long.
Figure 1 First model of soil particle catcher (Urban, 2011)
RESULTS
In the field measurements we tried to trap the moving soil particles, due to wind, through the
first prototype soil particle catcher. During these measurements, we also tested the efficiency
and the efficacy of the soil particle catcher to capture moving particles. The catcher was
freely situated on the soil surface in the prevailing wind direction and it trapped the moving
soil particles up to a height of 20 cm above the soil surface. The duration of each
measurement was always 60 minutes. The calculation of the quantity of particles captured per
unit area is very simple because the width of the entrance is 5 cm. Multiplying the width and
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length of erosive surface in the wind direction we can calculate the area of wind erosion
surface.
Model field in the Mo2enok Region
The evaluated soil unit in modeled field is 37. It is mainly a medium grade with typical
chernozems and carbonate on loess, for unit 31 - black soils typical and black soils gleyed,
medium and heavy, the loess slope and clay, and for 17 - black chernozems, mainly
carbonate, medium. According to the analysis of the BPEJ maps no soil susceptible to wind
erosion occurs, there is a more vulnerable soil type; black chernozem (HPJ 16) (fig. 2).
On 08.04.2011, during the second wind erosion event between 16:00 and 17:00
(measurement duration - 60 minutes) at an average wind speed of 5.7 ms-1 1,722 grams of
eroded soil was trapped in the soil particle catcher, which equates to 1299.6 kg.ha-1.hour-1 of
soil loss (soil particle catcher 5 cm wide with a north-western wind erosion surface length of
265 m)
On 13.4.2011, the second measurement at the same location during the fifth wind erosion
event between 10:00 and 11:00 at an average wind speed of 5.6 ms-1 364.4 grams of eroded
soil was trapped equating to 275.0 kg.ha-1.hour-1 of soil loss.
A third measurement was performed between 11:00 to 12:00 the same day in the same place
at an average speed of 4.3 ms-1. In soil particle catcher 199 grams of soil was trapped which
represents soil erosion of 150, 2 kg. ha-1.hour-1. The measurement site is shown in fig 29.
Analysing data (average minute data on wind speed and direction), provided by SHMÚ (from
the nearest meteorological station Nitra - Janíkovce), we found that in the area in the period
from the 5th to 15th April 2011 there were a total of wind erosion events. As an effective
erosive wind in our case we chose a wind speed which is higher than the critical wind speed
for loam soil by Pasák (1964). The recalculated critical speed at the height at which the
meteorological station measures is > 4.5 ms-1. The following tables show the average hourly
rate of effective erosive winds and their duration according different wind erosion events.
Figure 2 Map of present condition of fields 8 and 9 and BPEJ
Figure 3 Map of soil deflation and accumulation
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CONCLUSION
We performed field measurements of soil erosion with soil particle catchers designed by us.
We tested the first prototype of such a device which proved to be fit for purpose with easy
conversion of captured soil particles to quantities lost across the erosion area. During the first
week of April in 2011, we measured the intensity of soil erosion on black chernozems with
soil particle catcher. At modeled soil unit we performed a couple of measurements in order
to determine soil erodibility during a 60 minute period, the increase of soil erosion with
increasing erosive surface length as well as researching the soil loss at different heights. The
results of the wind erosion events analysis show that during the monitored period effective
erosive winds lasted a total of 58 hours. The most frequent average hourly wind speed ranged
from 5.0 to 5.9 ms-1 and the period of occurrence lasted a total of 28 hours. The maximum
average minute wind speed reached 12.3 ms-1 and a maximum gust of wind was 17.3 ms-1.
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Acknowlegment:
This paper was published with the financial support VEGA 1/0050/12 “Wind erosion
determination with mathematic modelation”
Contact address:
Ing. Lenka Lackóová, PhD., Slovak University of Agriculture in Nitra, Faculty of
Horticulture and Landscape Engineering, Department of Landscape Planning and Ground
Design, e-mail: [email protected]
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