Investigating Some Methodologies in Preparing Rill Erosion Map By Using RS and GIS
2006
Mohammadi Torkashvand, | Nikkami, Davud | Esfandyari, Mehrdad | Alavipanah, Kazem
Rill erosion map is one of the basic maps in erosion and sediment studies and watershed management programs. Some methodologies for preparing rill erosion map (1:250000) by using RS and GIS were compared in a research taken place Kan- Sologhan and Jajrood sub-basins in North-west and North-east Tehran, Iran. At the first phase, four working units' maps were prepared by integration a) plant cover, geology and slope b) land use, geology and slope c) land use, rocks sensitivity to erosion and slope and d) land use, rocks sensitivity to erosion and land unitsâ layers in Kan-Sologhan basin. For comparing the efficiency of four working unitsâ maps, 53 ground control points were investigated. Results showed that map "d" was better than "a", "b" and "c" in providing rill erosion regarding economic and executive considerations. At the second stage, map "d" was compared with three maps of e) land units f) rocks sensitivity to erosion and g) satellite image photomorphic units (ETM+ images) in a broader basin of Jajroud. Rill erosion intensities in 314 ground control points were controlled and ground truth rill erosion map was prepared. Rill erosion map has been crossed with different working unit maps. Results showed that the highest accuracy is related to the images interpretation (81.0% accuracy). Accuracy was 78.4, 66.8 and 59.9 percent for methods of "d", "e" and "f", respectively. Root Mean Squared Error was the highest for map "f" and the least for integrated layers method (map "d"). The greatest precision is related to image interpretation (with coefficient of variation of 20.5%). Totally, the images interpretation method is the better than other methods in preparation of rill erosion map.
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