流域长度

虽然长度不如密西西比一密苏里河，它的流域长度却居世界首位，流经的纬度达三十五度之多……”

Although falling short of the length of the Mississippi-Missouri , the Nile is at the head of all rivers as regards the length of its basin , which extends through 35 degrees of latitude ... "

由流水网计算的流域平均汇流路径长度和坡度等地形特征值随DEM网格的大小而变，故只能作为描述地形的相对指标。

Some topographic indexes derived according to the drainage networks , such as the mean length of flow concentration routes and the mean gradient of hill slopes , vary with the grid-size of the DEM , so they can only be used as relative indexes .

淮河流域洪涝具有不同长度的阶段性或周期性，存在约460年、150年和60&80年的周期及一些更小尺度的波动；

They have the periods with different time spans which are about 460 year , 150 year and 60 80 years and some shorter time span oscillations .

本文应用随机河网的理论对流域河网结构中的一些经验的定量关系（如Horton经验律、流域面积与长度、河频率与河网密度等）作了解释。

Some experienced empirical relations of the landforms of drainage channel network , drainage area , length , channel frequency and channel network density are explained with the random channel network theory .