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The Effect of Land cover Change on Run off and Erosion in Nam Chun, Lomsak, Petchabun, Thailand

Walyaula Watsusi, Cosmas Nicholas (2009) The Effect of Land cover Change on Run off and Erosion in Nam Chun, Lomsak, Petchabun, Thailand.

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Abstract:Land cover change dynamics and its impact on the environment and the reactions towards these changes calls for stakeholder intervention. Increasing conversion of natural cover is rendering the land cover vulnerable to destruction by the ever active functional processes such as runoff and erosion. Soil physical properties are destabilized and breaking its stability to resist the force of detachment, surface flow and erosion. With high rates of land cover change and effects on soil characteristics requires concerted efforts to identify and quantify critical areas where there is urgent need for attention. This study’s main objective was to identify and quantify land cover change in Nam Chun sub catchment. It was conducted in Nam chun sub catchment to estimate the rate of runoff and erosion caused by water erosion due to land cover change. Land cover change analysis was done to compare two maps of 2002 and 2007 of the same area after 5 years. It was established that land cover has undergone change in the five years. The most affected were the natural forest cover whose area had reduced by 42% of its original area and 22% of the total area of the sub catchment. Orchards and agriculture have increased at the expense of natural cover. Among the soil physical properties the saturated hydraulic conductivity (Ksat) was found not significantly different in all land cover types in the area. While crusting, bulky densities, porosity, cohesion by shear strength were all significantly different at P values of < 0.01 and < 0.05. LISEM model was used to asses run off and erosion. Two factors instrumental in affecting infiltration and runoff were considered. Ksat as a factor of land cover and rainfall were varied in the model for sensitivity analysis. It was discovered that much as there is land cover change in the area there was less influence by Ksat, on runoff. Rainfall amount has a higher influence. There was much surface flow detached in the catchment but no significant deposition in the area. The stream channel also had more detachment without the deposition. Peak discharge simulation showed that the orchards have the highest discharge than any other type of land cover. Change from natural to agriculture was found to be more vulnerable to erosion and increase in discharge than to natural cover. The results showed that the soil loss rate using flow detachment was consistently higher than the. The rate of discharge was also simulated in a small sub-catchment with in the Namchun catchment area and compared with daily measured stream discharge. The discharge rate simulated on an event basis was used to derive the total discharge rate. Comparisons of the results of the simulated and measured discharge rates showed that the simulated discharge was by far higher than the measured ones. This was especially because the measured discharge rate was mainly based on base flows of the stream when there was no enough rainfall and runoff. In general, from the study it is concluded that the incorporation of base flow in a stream using LISEM as a means of measuring runoff from fields within the sub catchment can be useful in considering assessment of erosion ii Key words: Land cover, Runoff, Erosion, Surface flow detachment, LISEM,Nam Chun sub catchment.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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