Chao Phraya watershed is the most significant watershed of Thaialand covers the total area of  20, 523 km2. The watershed has experienced the devasting flooding in 2011 which has affected 1.28 M of farmers and 2.01 M ha of agricultural areas in which 1.5 M ha was rice fields, 0.3 m ha was upland crops and 0.12 M ha was fruit trees and others. Runoff events from upland agricultural catchment to low land flood plains result from not only extreme rainfall events , topography and soil types but also by land uses and farming practices that affect soil water holding capacity and aggregate stability before and during rainfall events. Reliable informations of soil erosion and redistribution  rates in watersheds is an essesntial prerequisite for the design of target erosion and sediment control strategies and finally reduces the inpacts from flooding. Thirty-three bulk core soil samples were taken to a depth of 35 cm in areas represented three different land uses in three  sub-watersheds at different scales; site 1( Huai Yarai) covered an area of 4 km2, site 2( Huai Pongtalai) covered an area of 25 km2 and site3 ( Phu Kirio) covered an area of 10 km2. A mean soil erosion rate of 22.34  t ha-1 year-1 were determined for maize/ sunflower at site 1, 12.33 t ha-1 year-1 foe cassava and deposition rate of 5.25 t ha-1 year-1 for maize at site 2. Whereas at site 3, mean erosion rates of 19.38 t ha-1 year-1 were determined for maize and 36.74 t ha-1 year-1 for sugarcane. In conclusion , for the whole watershed, a net erosion rates of 22.34 t ha-1 year-1 were determined for maize/ sunflower , 12.33 t ha-1 year-1 for cassava, 14.13 t ha-1 year-1 for maize, and 36.74 t ha-1 year-1 for sugarcane. These findings provide good guidelines for future conservation practices and sustainable land uses program.

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