我国南部红土区的水土流失问题

SOIL EROSION ON THE RED SOIL REGION IN SOUTH CHINA

本文提出华南红土区水土流失的重大问题。水土流失的方式有:(1)坡面散流侵蚀;(2)暴流冲沟侵蚀。按风化分层出露情况可将花岗岩丘陵区的水土流失分为德庆崩岗型和五华沟谷型两大类。当风化层底部砾石层出露时,则地表呈“石蛋地形”,可用这种地表形态结构作为水土流失划分的指标。

Soil erosion on the red soil region in South China is not less serious than that in theloess region in North China.However,as the red soil erosion regions scattered widely theproblems were not easily focused on.Soil erosion in these regions is deepening day by day.Types of soil erosion in South China are divided into two.One is the sheet erosion andthe other is the gully erosion.In the red soil regions,the gully erosion happens accordingto the gully landform including the catchment basin,the gullies,and the alluvial fan.In thecatchment basin,the red earth layers make a cliff around the catchment basin.This is calledthe “crumble mouth” or the “crumble hills”.During rain season,a large column of sand andsilt floods down from the gullies and makes an alluvial fan at the mouth of the gullies.Thisnew fan will destroy houses,rice fields,roads and rivers.In the granite hills regions,red earth layers are divided into four layers.They are thered earth layer,the sandy layer,the pebble layer and the bed rocks layer in weathering.Ac-cording to this,the soil erosion is divided into two types.They are:the Deqing type,ofwhich the erosion begins at the red earth layer;the Wuhua type,of which the soil erosion hap-pens in the sandy layer where the red earth layer was eroded out.The first type is called thecrumble mouth type and the second type,the gully type.If the two layers are eroded out,the gullies cannot develop on the land surface.Thesheet flow becomes the dominant force of the soil erosion.At this stage,the pebbles landformwould appear.