side gradient

例句：

1. 1. The side gradient of the mountain is steep.
   这座山的侧面梯度陡峭。
2. 2.The side gradient of the road is changing as we go further down.
   随着我们继续往下走，道路的侧面梯度在变化。
3. 3.The side gradient of the river is important for navigation.
   河流的侧面梯度对于导航很重要。