基于地形地貌参数确定地貌单位线中的平均流速

Determination of Average Flow Velocity in Geomorphologic Instantaneous Unit Hydrograph Based on Terrain andTopographic Parameters

无资料地区的汇流计算在山丘区洪水预报中至关重要。现有的地貌单位线虽然提出了解决方法,但对于其中的汇流速度仍缺乏有效的确定方法。选取了155个互不嵌套的源头型流域,利用率定优选的方式求出流域最优表征的平均流速,以此代表流域实际的平均汇流速度。从所有流域中随机挑选出117个流域,利用Spearman相关性分析和随机森林模型分析了地形地貌参数和流域最优表征平均流速之间的相关性。结果表明,最高级河长LΩ和最高级河流的海拔落差DΩ是对流域最优表征平均流速影响程度最高的因子。构建了LΩ和DΩ同流域最优表征平均流速之间的函数关系,并在率定及剩余的验证流域上对计算流速和最优表征流速之间的相关性进行验证,二者相关性良好,确定性系数分别为0.557和0.588。将此方法移用于海南定安河流域的洪水模拟中,模拟效果良好,表明所提方法具有一定的可靠性和通用性。

The calculation of runoff concentration for ungauged watersheds is especially crucial in the flood forecasting of hills.Although the present concepts about geomorphologic instantaneous unit hydrograph have proposed the solution,convergence velocity describing flow characteristic in a watershed is required to be estimated.Here 155 source watersheds have been selected,and in order to represent the real average confluence velocity of the basins,the optimal velocity can be obtained by determining the optimum utilization ratio of the watersheds.Spearman Correlation Analysis and Random Forest model are used to analyze the correlation between topography and geomorphology parameters and the optimal representative mean velocity in 117 watersheds randomly picked out from total subsequently.Results obtained indicate that the highest-level stream length and the highest-level stream elevation difference are more important topographical factors that affect flow velocity.The formula established between the optimal flow velocity of the watershed and the terrain and geomorphic factors is tested in calibrated and the remaining validated watershed,where performance shows the correlation coefficient are 0.557 and 0.588 respectively.Application of the formula shows better results when transferred to Dingan river in Hainan Province.The results indicate that the proposed technique has perfect fitting accuracy.