The watershed line of the symmetrical watershed is located in the center of the watershed, and the slopes on both sides have the same steps and lengths. The watershed line of the asymmetric watershed is biased to one side of the watershed, and the slopes on both sides are asymmetric. In nature, symmetric watershed is extremely rare, while asymmetric watershed is widely developed.
Extended data:
1. In the young folded mountainous area, denudation has not completely changed the original mountain shape, and asymmetric folded wings will inevitably lead to asymmetry of the watershed. In the long-term denudation area, the difference of lithology or the influence of faults often cause asymmetry on both sides of the watershed. In the monoclinic structure area, the watershed formed by a single mountain is often steep and gentle.
2. The height of the river datum in the adjacent basin and its distance from the basin. They directly determine the slope of the river, as well as the erosion capacity of the river and the erosion speed of the hillside. Generally speaking, when the distance between the basin and the river datum on both sides is equal, the river erosion and hillside erosion ability of the side with low river datum is stronger than that of the high side, so the slope of the low side is steep and the slope of the high side is gentle.
Similarly, when the height of the river base level on both sides of the watershed is equal, the slope of the river base level near the watershed is large and the slope on the other side is small. In addition, the uneven precipitation on both sides of the basin also has an impact. On the rainy side, the river flow is large, the surface runoff is rich, and the river erosion or hillside erosion is stronger than the other side, so the terrain is steep.
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