The Evolutionary Model Of River Terraces In The Mid-tail Of WeiHe River

This theme selected WeiHe River round TianShui, JinHe River round BinXian, BaHe River round LanTian and LuoHe River round LuoChuan to study the evolutionary model of river terraces in the mid-tail of WeiHe River . We have built the cross-section of each river, and analyzed the evolution of each river terrace in the mid-tail of WeiHe River according to the velocity of downcuting and lateral erosion.We got the age of the river terraces by the sequence of the loess and paleosol on the river terrace. TS was formed in 1.2 Ma BP, T4 was formed in 0.82Ma BP, T3 was formed in 0.5-0.6 Ma BP, T2 was formed in 0.13 Ma BP, T1 was formed in 0.01 Ma BP. The formation of the river terraces in the mids-tail of WeiHe River is almost synchronous.The evolution of the river terraces in the mid-tail of WeiHe River has these characteristics. Their downcuting velocity accelerates except LuoHe River round LuoChuan. The erosion velocity of WeiHe River round TianShui and JingHe River round BinXian reduced, and the lateral erosion velocity of LuoHe River round LuoChuan reduced. This may be due to the reduced flow. The lateral erosion velocity of BaHe River round LanTian accelerates,this may be resulted from the accelerating uplift velocity of LiShan mountain.In the end, we forecasted the evolutionary trend of the river terraces in the mid-tail of WeiHe River according to their evolutionary characteristics.