The Erosion hazard in Nam Chun Sub watershed, Phetchabun Province was assessed by C. Saengthongpinit (2004), H. Solomon (2005) and M. suriyaprasit (2008)
and some other MSc. Student of ITC within the project.The following paper is extract from their researches.
Background
Soil erosion is one of the most serious land degradation problems all over the world. It is a hazard traditionally associated with agriculture in tropical and semi-arid areas and is important for its long-term effects on soil productivity and sustainable agriculture (Morgan, 1995). Soil erosion has the long-term impacts on soil quality, agriculture productivity, movement of pollutants, ecological diversity in streams and wetlands, river channel change and effects on flooding. Total land area affected by water erosion all over the world is 1,094 Mha and that by wind erosion is 549 Mha (Oldeman, 1994). Soil erosion has been problem ever since land was first cultivated. It reduces not only topsoil but also organic matter, nutrient, and available soil moisture. . Furthermore, it reduces the capacity of rivers and drainage ditches which leads to the risk of flooding and blocking irrigation canals. Morgan (1995) reported that increasing farm size is often accompanied by large-scale earth moving and land levelling operations, which make the soil more erodible. Poudel et al.(2000) reported that soil erosion is considered a major constraint to sustainable vegetable production in Southeast Asian steeplands. Factors responsible for erosion are climate, topography, soil, landcover, landuse and management practices. Preventing or controlling soil erosion relies on selecting appropriate strategies for soil conservation, which requires a thorough understanding of the process of erosion. Many strategies for erosion control have been applied such as crop and vegetation management and soil management. However the plant cover and the presence or absence of conservation measures influence very much the rate of erosion.
Land degradation is a process that lowers the capacity of land. According to FAO (1994), there are six types of land degradation: water erosion, wind erosion, soil fertility decline, salinitation, water logging, and lowering of the water Table. The unbalance between land resource regeneration rate and population growth rate leads to lack of suitable land for agriculture (Vargas Rojas, 2004). Unless soil conservation and management practices are implemented properly, soil erosion can cause loss of plant nutrient, weak soil aggregation and finally low agriculture production. Improper land use practices in sloping areas accelerate soil erosion.
Soil erosion not only reduces soil depth, but also reduces the capacities of soil such as water holding and decrease plant nutrient. In the long term, soil productivity will be decreased. Furthermore it can cause offsite effects including pollution in water, downstream sediment in river bank and reservoirs. It is necessary to understand erosion and sedimentation process for soil conservation planning.
Objectives
In this study, The Limburg Soil Erosion Model (LISEM) was used to quantify the amount of runoff in the upper catchment that take into account effect of land cover change and also how different factors affect surface runoff. The LISEM is constructed with the PCRater dynamic modelling language (Wesseling et al., 1996) which allows great flexibility. Moreover, on a GIS level LISEM uses a raster type representation of the catchment which allows detailed representation of the processes. In case of limited data availability, the user can also choose Green and Ampt or the Holtan equation for infiltration calculation (De Roo, 2000). The results show not only the total runoff at the outlet but also the amount of sediment.
1. To assess soil erosion in Nam Chun sub-watershed, Thailand using models while incorporating terrain parameters in soil loss assessment. Incorporation of hydrological terrain parameters is proposed in this study to increase information on soil erosion assessment. The idea is to use sediment transport index (STI) to replace the slope gradient in the revised MMF model.
2. To assess erosion prone areas in inaccessible mountain areas.
References
FAO, 1994. Land degradation in South Asia : it's severity, causes and effects upon the people. World Soil Resources Reports : FAO;78. FAO, Rome, 100 pp.
Morgan, R. P. C., D.D.V., Morgan., and H.J., Finney. (1984). A predictive model for the assessment of soil erosion risk. Reprinted from: Journal Agricult. Engineering Res. 30, 245-253.
Oldeman, L. R. (1994). The global extent of soil degradation. Reprinted from: Soil resilience and sustainable land use, pp.99-118.
Poudel, D. D., Midmore, D. J., and West, L. T. (2000). Farmer participatory research to minimize soil erosion on steepland vegetable systems in the Philippines. Agriculture, Ecosystems & Environment 79, 113-127.
Saengthongpinit, C., 2004. Soil erosion assessment using revised MMF equations With special reference to terrain parameter(s) : a case study in Nam Chun sub-watershed, Lomsak district, Thailand. MSc Thesis, International Institute for Geo-Information Science and Earth Observation, Enschede, 80 pp.
Suriyaprasit, M. 2008. Digital terrain analysis and image processing for assessing erosion prone areas: A Case Study of Nam Chun Watershed, Phetchabun, Thailand. MSc Thesis, International Institute for Geo-Information Science and Earth Observation, Enschede, 97 pp.
Vargas Rojas, R.J., 2004. participatory land suitability assessment using integrated Toposequence analysis : Nam Chun sub watershed, Petchabum province, Thailand, ITC, Enschede, 58 pp.
Development of Methodologies for
Land Degradation Assessment Applied to
Land Use Planning in Thailand
FAO, 1994. Land degradation in South Asia : it's severity, causes and effects upon the people. World Soil Resources Reports : FAO;78. FAO, Rome, 100 pp.