Following the basin wide heavy flood on Changjiang River in 1998, a significant flood occurred in 1999. Comparative analysis of both floods in terms of flows and flooding situations shows that both floods had one comm...Following the basin wide heavy flood on Changjiang River in 1998, a significant flood occurred in 1999. Comparative analysis of both floods in terms of flows and flooding situations shows that both floods had one common feature, that is, the flood stages were fairly high. But they differed greatly at the same time, that is, the 1998 flood was a basin wide heavy one while the 1999 flood was a significant local one. At Yichang station there occurred eight flood peaks in 1998, while in 1999 only three peaks took place. The maximum peak discharge at this station in 1999 was 57 600 cubic meters per second, which was smaller than that in 1998. The maximum flood-volume in 30 d of the 1998 flood at this station equaled that in 1954, when an extraordinary heavy flood happened on the River, while the maximum flood-volume in 30 d in 1999 was 25.8 billion cubic meters per second smaller than the 1998 one. It is seen that inflow floods from the upstream Changjiang River (above Yichang) in 1999 were not so big. Comparison of flood volumes in longer period shows that the 1999 flood was relatively concentrated while the 1998 one had lasted longer duration. Analysis shows that flooding situations in both years differed significantly in terms of the flood volumes diverted from river channels due to dyke breaches and collapses, the cases of polder embankment collapses, the areas of inundated cultivated land and the numbers of dangerous events for hydraulic structures. These differences had been resulted from the different properties of both floods and the dyke strengthening efforts made after the 1998 flood. It is seen that flood control engineering constructions initiated in the days following the 1998 flood have played an important role in fighting the 1999 flood.展开更多
文摘Following the basin wide heavy flood on Changjiang River in 1998, a significant flood occurred in 1999. Comparative analysis of both floods in terms of flows and flooding situations shows that both floods had one common feature, that is, the flood stages were fairly high. But they differed greatly at the same time, that is, the 1998 flood was a basin wide heavy one while the 1999 flood was a significant local one. At Yichang station there occurred eight flood peaks in 1998, while in 1999 only three peaks took place. The maximum peak discharge at this station in 1999 was 57 600 cubic meters per second, which was smaller than that in 1998. The maximum flood-volume in 30 d of the 1998 flood at this station equaled that in 1954, when an extraordinary heavy flood happened on the River, while the maximum flood-volume in 30 d in 1999 was 25.8 billion cubic meters per second smaller than the 1998 one. It is seen that inflow floods from the upstream Changjiang River (above Yichang) in 1999 were not so big. Comparison of flood volumes in longer period shows that the 1999 flood was relatively concentrated while the 1998 one had lasted longer duration. Analysis shows that flooding situations in both years differed significantly in terms of the flood volumes diverted from river channels due to dyke breaches and collapses, the cases of polder embankment collapses, the areas of inundated cultivated land and the numbers of dangerous events for hydraulic structures. These differences had been resulted from the different properties of both floods and the dyke strengthening efforts made after the 1998 flood. It is seen that flood control engineering constructions initiated in the days following the 1998 flood have played an important role in fighting the 1999 flood.
