基于流量-面积比值的小流域设计洪水计算方法对比研究

Comparison of Calculation Methods for Design Flood of Small Catchments Based on Flow-Area Ratio

为确定分布式模型法、地区瞬时单位线法及推理公式法在估算山区小流域设计洪水过程中的适用性,基于洪峰流量-流域面积比值,以重庆市綦江区蒲河水系为研究对象,采用3种方法分别进行设计洪水计算,并与重庆市实测100 a一遇洪峰流量进行对比。结果表明:(1)当流域面积<10 km2时,采用推理公式法更合理可靠;此时河道坡度较大,流域的产、汇流条件符合推理公式法假定条件,计算结果符合实际。(2)当流域面积为10~100 km2时,分布式模型法与地区瞬时单位线法均可合理计算设计洪水,但前者计算结果比后者更接近实测值。此类流域河道长、坡度平缓,流域的水动力在空间中可视为均匀的扩散;计算格栅单元间连续性强,各栅格向流域出口演算能合理反映真实的设计洪水过程。(3)当流域面积>100 km2时,3种方法计算结果与实测值均有不同程度的偏离,但分布式模型法偏离程度最低,可作为设计洪水计算的首选方法。研究结果将有助于合理选择设计洪水计算方法,为类似山区小流域设计洪水计算提供参考。

The design flood in a mountainous small catchment was calculated by using distributed model,regional instantaneous unit hydrograph,and deducted formula respectively based on the ratio of peak discharge to catchment area,and the calculated results were further compared with the measured peak discharge of 100-year flood to determine the applicability of the above-mentioned three methods. Puhe river system in Qijiang,Chongqing was selected as a case study. Conclusions are drawn as follows: 1) deducted formula is more accurate and reliable for catchment with an area smaller than 10 km^2 as steep river slope makes the runoff yield and concentration condition consistent with the assumption of the deducted formula; 2) distributed model and regional instantaneous unit hydrograph are both applicable to catchment with an area between 10-100 km^2,with the result of the former closer to measured result; in such catchment of long channel and gentle slope,the hydrodynamic dispersion can be regarded as uniform diffusion in space,and the computation grid units are strongly continuous,well reflecting the real design flood process; 3) distributed model is recommended as the preferred method when catchment area is larger than 100 km^2,as it deviates to the smallest extent to the measured value among the three methods. The conclusions will be helpful to the selection of a reasonable calculation method.