Why shouldn't houses be built under the cliff at the end of the mountain?

Why shouldn't houses be built under the cliff at the end of the mountain?

Facing the house in front of the mountain tail or Taniguchi, it is difficult to live fortune, and it is easy to get all kinds of diseases. The so-called front of the mountain tail refers to the area below the slope where the foot of the mountain ends and the steep slope is connected to the flat ground. The valley exit, that is, the narrow valley between the two mountains enters the gentle part of the flat land. If it is in a wide plain, there will be rivers flowing through it. People living in these two types of terrain are always at risk of being attacked by floods and landslides.

The above-mentioned topography is called fan-shaped topography in geography. Once the rapidly descending narrow valley stream enters flat ground, its velocity suddenly slows down, so the sand brought by the stream is deposited at the mouth of the valley. Especially in the flood season, a large amount of sand and soil caused by landslides fell with the flood and piled up at the exit of the valley, forming new land.

But if you look at the backside, the floods and landslides that created this fan-shaped land do not know when it will come again. Therefore, the danger will never be eliminated. Those who live in such areas will be worried whenever heavy rain comes, and it will be difficult to guarantee that they will not get sick for a long time.