People's perception and socioeconomic determinants of soil erosion: A case study of Samanalawewa watershed, Sri Lanka

Though soil erosion is an important concern in Sri Lanka, there is a dearth of baseline information on soil erosion in many of its watersheds, which obstructs monitoring of soil erosion and mitigating its effects. In order to assess soil erosion in a critical watershed and to identify its determinants, the Samanalawewa watershed, which contains one of the main hydropower generating reservoirs in Sri Lanka, was selected for this study. Remote-sensing (RS) and geographic information system (GIS) based modeling as well as field experiments were employed to assess and map soil erosion rates. Results indicated that the current rate of soil erosion ranges from 0 to 289 t/ha/yr, and that the average rate of soil erosion has been declining from 20 to 4 t/ha/yr over a period from 1986 to 2008. The current rate of soil erosion is, however, still about 14 to 33 times greater than the natural soil generation rate. Socioeconomic factors and peoples' perception of soil erosion and soil conservation measures were examined using data collected through a household survey. Multiple regression analysis with eighteen covariates of socioeconomic characteristics yielded eleven socioeconomic variables, viz. household size, farm labor, education, land tenure, conservation cost, training, committee membership, professional competencies, income, distance, and financial capital as the predictor variables of soil erosion. Farmers identified improper soil and crop management practices as the major causes of erosion. The adoption of conservation measures, their effectiveness, and their impact on ecosystem services were also examined.