Geomorphic change of the Young `San River, during in 1979. 8. N12, were measured by field survey. Such fluctuations in channel depth and width with channel shape compared with during 1948, 1974map, 1979 river channel and Hydraulic yearbook ( 92 : 19 78). Dam Yang Dam at upstream are threatened by eventual filling in by silt carried from upstream. The stream below the Dam Yang Dam increased its velocity of flow. The dependence of erosion upon velocity and discharge ismost impressive durin?; floods. The flood discharge of most rivers is many times that at low water. The Young San River, notorious for its destructive floods has a ratio annual maximum to minimum flow of 110 to 10. The greater the stream velocity increases by manmade levees after the year 1970. Young San River, after the year 1970, cut rapidly a channel deep, wide and meander cutting. Through midstream, the greater the stream velocity, by mangy-made levees, forming meander cutoff, becomes relatively narrow, irregular channels, Because ofchauging shape the channel, Kung Am, San Dong. Duk Heung., Won Dang, Sa Wol Dle meander cutting was deepened, the bank of the stream are worn away. Therefore the added velocity and discharge greatly increased the streams power in that place. In the process, the Channel was greater deepered as artificial changes(catch-sand). Although the young San po at down stream deposit the resulting load downstream. Therefore Young San River changes by year to year of river channels by :meander cutting and by artificial stream(lever, dam, bridge).