Monday, February 8, 2016

GIS Application for Soil Erosion Assessment

The study focused on assessing quantitatively the soil erosion using the Revised Universal Soil Loss Eq. 2 (RUSLE2)  model with the help of remote sensing and GIS in a subwatershed in the catchment of Krishnagiri reservoir in Tamil Nadu, India. “Land degradation from water-induced soil erosion is a serious problem in India and thus it forms an important social and economic problem.” (p.83)

Soil erosion affects soil fertility and crop yields by removing organic matter from the soil and breaking down the soil structure. It is a “three-stage process: detachment,transport and deposition. The factors that influence the rate of soil erosion include rainfall, runoff, slope, land cover and the presence or absence of conservation strategies.” (p.84) Thus, the study estimated erosion for each hill slope unit by considering “intensity of rainfall, type of soil, land use classification, and the existing soil conservation practices.” (p.84)

“A data base was created with all the subfactor values for the hill slope units. Incorporation of remote sensing technique and Geographic Information System (GIS) made the spatial analysis of the study more reliable and accurate. The annual average soil erosion rate is estimated as 25 t/ha/year, which is on a higher range.” (p. 83)
Four topographic maps of the region were scanned to cover the whole subwatershed  and then georeferenced. “The subwatershed boundary was delineated and digitized. The drainage patterns, contour lines, roads, towns etc. were identified and digitized to create different thematic layers. Based on the order of the streams and terrain characteristics the whole area is subdivided into small hill slope units. The number of hill slope units chosen is 48 and is shown in Fig. 2.” (p. 94)

After aggregating the different factors such as soil erodibility and slope length and steepness the researchers estimated and annual average erosity of 81.6 (MJ mm)/(ha h) for the Veppanapalli subwatershed during the year 2003. (p. 99) The map below shows different soil loss ranges in sub-watershed divided into the 48 hill slope units.

With the help of erosion models and GIS excessive soil loss can be predicted. Therefore better conservation strategies can be undertaken to prevent it benefiting  in this case Tamil Nadu and India as a whole socially and economically.

Source: Ismail, J., & Ravichandran, S. (2008). RUSLE2 model application for soil erosion assessment using remote sensing and GIS. Water resources management, 22(1), 83-102.

I have acted with honesty and integrity in producing this work and am unaware of anyone who has not. -Ilka Vega

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