基于数字高程模型的等流时线推求与应用

Derivation of DEM-based isochrones of watersheds

根据流域等流时线的原理 ,详细探讨了基于数字高程模型 (DEM )的等流时线的推导方法 .根据汇流流速与地表坡度的水力学关系 ,提出了一个经验公式来计算水流流经DEM上每一栅格的时间 .当水流流向采用多向分配法而不是单向流法时 ,提出了两种计算汇流时间的方案 .在爱尔兰的一个中型流域上进行了应用研究 .与传统的在地图上人工经验勾绘出来的等流时线相比 ,基于DEM的等流时线具有两个优点 .一是能够充分反映流速空间变化的非均匀性 ,二是自动生成 ,当流域地形发生变化时 。

The method of deriving isochrones from the digital e levation model (DEM) of watersheds is discussed in detail, according to the prin ciples of the isochrones. Based on the hydraulic relationship between the flow v elocity and the slope, an empirical formula is proposed to calculate the time fo r traveling through each grid of DEM. When the multiple flow direction method ra ther than the single flow direction method is employed to determine the flow dir ection, two schemes are suggested to calculate the concentration time from each grid to the watershed outlet. An application example on an Irish watershed is pr esented. Compared to the isochrones obtained by empirically drawing lines on th e topography map, the DEM-based isochrones have two advantages. The first one i s that they are able to reflect the unevenness of the distribution of flow veloc ity over the watershed, and the other is that they are automatically abstracted and can be easily modified if the topography of watershed is altered.