中文摘要：

洪水流量计算中河道糙率是一个重要的灵敏度参数。以汉江上游郧县尚家河台地前沿记录的四期古洪水流量计算为例,研究河道糙率系数在比降-面积法和HEC-RAS模型中对古洪水流量计算结果的影响。结果表明：其他水文参数一定时,河道糙率系数以±15%变幅,比降-面积法重建的古洪水流量变幅在-13.04%~17.65%,HEC-RAS模型计算的流量变幅在-4.32%~4.57%;若河道糙率系数以±25%变幅,比降-面积法和HEC-RAS模型计算的流量变幅分别为-20%~33.33%和-7.79%~9.18%,说明采用HEC-RAS模型重建古洪水流量,可减少河道糙率系数对计算结果的影响,使古洪水流量计算结果更为可靠。此外,假定其他参数不变,主河槽和左、右岸糙率系数依次变幅±25%,主河槽糙率系数变化对流量计算结果影响最大,说明洪水流量计算时应准确选取主河槽的糙率系数。该结果对水利工程建设具有重要的现实意义。

英文摘要：

Palaeoflood hydrology is a newly developed frontal subject in global change science. There several models could be used to calculate palaeoflood discharge in the bedrock channel according to the palaeoflood slackwater deposits （SWD）, but the channel roughness is a complex sensitivity parameter in flood discharge cal- culation. Taking 4 period palaeofloods recorded in the Shangjiahe platform frontier in the Yun County bedrock reach of the upper reaches of the Hanjiang River as an example, the influences of the channel roughness coeffi- cient were studied by using the slope-area method and HEC-RAS model to calculate the palaeoflood discharges, respectively. The results showed that when other hydrologic parameters didn＇t change, and if the channel compre- hensive roughness coefficient only changed about ：t： 15%, the errors of palaeoflood discharges were-13.04% ~ 17.65% with the slope-area method, and -4.32% - 4.57% with HEC-RAS model, respectively. And if the channel comprehensive roughness coefficient only changed about ：t：25%, the errors of palaeoflood discharges were-20% ~ 33.33% using the slope-area method and -7.79% ~ 9.18% using HEC-RAS model to reconstruct palaeoflood dis- charges, respectively. This indicated that HEC-RAS model could effectively reduce the influence of roughness coefficient to reconstructe palaeoflood discharges, and the palaeoflood discharges calculation was more reliable. Moreover, if the roughness coefficient of the main channel, left bank and right bank changed ±25% respectively, the discharge change of the main channel roughness coefficient has the greatest influence on the results of dis- charge calculation. This also indicated that it was very important to select accurately the main channel roughness coefficient to calculate flood discharge. The results provided a theoretical basis for the hydrological engineering calculation and flood control and disaster mitigation.