Abstract: Field observations and measurements of historical floods at Yulin Cave in the year of 1911 were conducted.The flood area was measured using a Leica TS06 Total Station,and the integration method was used to calculate flood area.The stage-discharge and slope-area methods were applied to calculate the peak discharge,and the rank method was used to calculate the recurrence intervals.Peak discharge values calculated by the stage-discharge and slope-area methods were 879 m³·s^-1 and 738 m³·s^-1 respectively.These two results were similar,and their difference was only 9.6%.Therefore the mean value of 809 m³·s^-1 was taken as the estimated peak discharge. Furthermore,the calculations using the rank method suggested that a recurrence interval for the flood magnitude in the year of 1911 was 105 years. This work extended the flood record period for the Yulin River,and could provide a reliable basis for constructing flood control facilities at Yulin Cave in the context of global warming.

Key words: historical flood, stage-discharge method, slope-area method, peak discharge, recurrence interval, Yulin Cave, Gansu