汛期洪水水沙组合对潼关河床冲淤的影响

Effect of River Flow and Sediment in Flood Periods upon Elevation at Tongguan

汛期潼关河床冲刷主要发生在洪水期 ,平水期微淤或处于冲淤相对均衡状态。洪水水沙组合情况是决定潼关河床是否发生冲刷的基本条件 ,河床边界条件对洪水冲刷产生影响。 1974年以来 ,使河床发生冲刷的洪峰占 6 9% ,潼关高程升降值一般小于 0 .30m ;使潼关高程下降 0 .5m以上的主要是流量大于 5 0 0 0m3 /s的各级含沙量洪峰 ;使潼关高程上升 0 .5m以上的 ,以流量小于 5 0 0 0m3 /s、含沙量大于 2 0 0kg/m3 的洪峰居多。近期潼关洪峰少、流量小、含沙量高 ,导致洪水期潼关高程下降值比前期偏小 5 0 %左右 ,是河床逐年淤积升高的主要原因。

In flood periods river bed erosion near Tongguan mainly takes place in the big flood periods while the river bed in a condition of being little accretion or being in equilibrium when in small flood periods. Incoming flow and sediment are the basic elements deciding whether or not the river bed at Tongguan is under erosion while the channel boundary also has some influence on it. Since 1974, of all big floods, there are 69% that caused the erosion with the elevation decreased by less than 0.30 m. What caused the elevation to be decreased by more than 0.50 m are mainly the big floods with discharges more than 5 000 m 3/s. What caused the elevation to rise by more than 0.50 m are mainly the floods with discharges less than 5 000 m 3/s and the corresponding sediment concentration more than 200 kg/m 3. In the near past years, hydrological regime at Tongguan featured the small floods and high concentration, which caused the decrease in the elevation in flood periods to became 50% less. This is the main reason for annual rising in the elevation.