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- Prediction of Soil Erosion in Northern Thailand Using a Physical Model
Prediction of Soil Erosion in Northern Thailand Using a Physical Model
Dissertation Abstract:
Experiments were conducted to study the effects of rainfall intensity, slope steepness, and crop cover on runoff and soil loss. The physical model of estimating soil erosion as developed by Rose, Barry, and Sander (1983) was evaluated, and the simplified equation was used in predicting soil erosion of two watersheds (Haui Pong and Nam Poi) in Chiangmai, Thailand.
Treatments involved two soil types (Korat sandy load and Pak Chong clay loam, both belonging to Oxic Paleustults), three levels of rainfall intensity (60, 90, and 120 mm/hr), four levels of slope steepness (0, 5, 10, and 20%), and two kinds of cover crops (corn and soybean). Rainfall intensities were controlled using a rainfall simulator and slope steepness using a slope-adjustable soil trough.
Runoff, sediment concentration, and soil loss increased with increase in rainfall intensity and slope. Sediment concentration was high at the earlier stage of crop growth, but this exponentially decreased as the vegetative cover increased with time. The sediment concentration in Pak Chong clay loam was generally lesser than in Korat sandy loam, particularly under higher rainfall, steeper slope, and lesser vegetative cover, indicating that the latter soil was more erodible than the former.
The physical model yielded good prediction of soil erosion. In both soils, under bare or cropped soils surface conditions, the correlations of the predicted and the measured soil loss on different combinations of slope and rainfall intensity were highly significant. In the two watersheds, the predicted soil erosion values in the forest and the well-vegetated and level agricultural lands were less than 4 t/ha/yr. On the other hand, the hilly areas used for shifting cultivation gave the highest value (1,208 t/ha/yr).
