1. INTRODUCTION 
Soil erosion is a complex various natural 
process, which results decrease in fertility of 
the land and reduction of crop yields. Erosion is 
very high in Asia, Africa and South America 
averaging 30-40 t ha” year! (Borrow 1991). 
The world's natural resources and ecological 
problems are threatened by erosion. About 
25x10" t of soil are eroded into seas every year 
by surface run off and6x10°ha of productive 
agricultural land is deserted in world 
(Anonymous, 200). After the long process soil 
is formed. Physical, chemical and biological 
activities have been easily eroded and supply of 
sediment by the change of land use pattern such 
as deforestation and agricultural activities in 
the upper catchments, development of 
floodplains, urbanization in lower catchments. 
Sediment load effects on water quality 
degradation, loss of primary production and 
benthic habitats. It increase in flooding and an 
increased cost associated with removal of 
sediment in navigation channel and with 
shortening the economic life of hydraulic 
structures (woods, 1984;  Pringle1986; 
Kinsey1990; Robertson and Lee Long, 1990; 
Edwards, 1991; Arakel et al, 1993; Arakel 
1995; Erskine and Saynor 1996a, 1996b: 
Erskine, 2003). 
The soil erosion is the natural process of 
combination of historical and 
geomorphological analysis. The rate of spatial 
and temporal distribution of the soil erosion 
depends on the interaction of physical and 
human circumstances. The land degradation 
stems from a combination of changes in land 
use, agricultural intensification and intense 
rainstorms. Erosion may also be exacerbated in 
the future in many parts of the world because of 
climatic change towards a more vigorous 
hydrologic cycle (Amore et al., 2004). 
Phewa lake watershed territory consists of 
acidic, moderately fine textured and non-stony 
clay (LRMP, 1983). Colluvial deposits can 
exceed 15 m in the depth owing to the mass 
movement near Pame (Ramsay, 1985). Soils 
  
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
with loamy skeletal texture are found in hilly 
areas (Mulder, 1978). Sand, silt and clay are 
found in the area. Bright reddish, dark reddish, 
brawn and dark brawn soils are found in the 
different parts of the Phewa lake watershed 
area (Lamichhane, 2000). The results estimated 
annual sedimentation deposit in whole Phewa 
Lake varies from 175,000 to 225,000 m? . 
A growing world population and the 
abandonment of large areas of the formerly 
productive land as a result of erosion, 
salinization or alkalization which is the 
conventional wisdom favors explaining erosion 
as a response to increasing pressure on the land. 
The previous study shows that about 5 decades 
time period half of the area of the Phewa Lake 
converted into land. There is the severe 
problem of changing lake into land due to the 
rainfall, climate change, pollution, 
sedimentation and land encroachment and other 
human activities. 
Phewa Lake is in mesotrophic situation and 
going to on state of eutriphication due to the 
environmental hazards and sedimentation. The 
lake is sediment eroded from debris of the 
Harpan Khola, Andheri Khola and its 
tributaries. From the hilly region of its 
watershed has the problem of flood and 
landslide due to the deforestation. Therefore, 
the study of the lake in climate change, 
sedimentation and environmental perspective 
study is essential. The previous study deals 
with the one or two related issues in soil 
erosion, sedimentation with some observation 
and modeling but not integrating participatory 
GIS approach for the generation of rule and 
policy as well as the activities of the all 
stockholder's of the watershed area. This study 
includes this approach for the reduction of the 
soil erosion in the watershed area. The 
objectives of this study is locate the erosion hot 
spots and land slide effects on soil erosion and 
sedimentation, to find out the ratio of soil 
erosion and sedimentation that has been the 
process of lake converted into land, to find the 
effects of climate change in soil erosion and 
sedimentation 
   
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