APPLICATION OF Z-INDEX METHOD TO FLOOD DISASTER EARLY WARNING IN THE LOWER YELLOW RIVER

In this study, we collected the the daily precipitation data of 10 stations, and analyzed the sediment delivery pattern of 150 floods in the lower Yellow River from 1968 to 2007. Z-index method was innovatively applied to flood disaster early warning in the Lower Yellow River. The sediment delivery characteristics, flood time distribution characteristics and basin floods in the river was investigated respectively. The results showed that the sediment delivery ratio (SDR) decreases rapidly with the increase of average sediment concentration and average sediment coefficient, and there is an optimal flood level to maximize the sediment delivery rate. The sediment delivery ratio of the flood is negatively correlated with the maximum sediment concentration of the flood. When the maximum sediment concentration C-max is greater than 300 kg/m(3), the SDR is less than 0.50, indicating that the sediment delivery volume of high sediment concentration flood is relatively low. In terms of time distribution, the flood in the lower Yellow River mainly occurs from late June to early July and late August, and may also occur in mid-April and early October. From the perspective of basin flood index, each flood process can be reflected in the flood index, and its intensity can also be well matched. In addition, the flood index is reflected in the day before the occurrence of floods at all grades, which shows that the Z-index method has a certain prospect in predicting flood disasters.