黄土丘陵区沟谷发育及其稳定性评价

本研究选择黄土高原北部丘陵区无定河两个支流米脂河，金鸡河，在对其流域系统河道级数，冲沟和坳沟发育时期进行划分与判断的基础上，计算了各级沟谷及坳沟的“宽深比”，并对其进行了对比分析。研究表明黄土沟谷发育中冲沟发育阶段是沟谷稳定性最差的阶段，而坳沟阶段是沟谷发展的稳定阶段，稳定性的差异可由沟谷Ｗ／Ｄ值来定量化，据此可预测黄土丘陵区尚有数十万年的沟谷不稳定时期即强水土流失期。

DEVELOPMENT OF GULLIES AND EVALUATION ON THEIR STABILITY IN THE LOESS HILL REGION

The Loess Plateau is a region with the most serious soil erosion in the world. The process of soil erosion in the region appears on the rapid elongating, violent cutting and extensive widening of gullies. Therefore, it has a significance to analyze the process of soil erosion and its changing tendency based on the development law of gully land form, in other words, to understand the inherent law of soil erosion on the Leoss Plateau, researches should be started with on the stability of the loess gullies. The gullies develop extremely in the loess hill region in the northern part of the Leoss Plateau, and soil rosion is serious in Mizhi region. In this paper, the Mizhi River and Jinn River basins, the tributaries of Wuding River which is one of the first grade tributaries of Yellow River, are selected as the research area of development and stability of the loess gullies, and they have representativeness. Based on the judgement and determination of river rank number and development stage of the loess gullies, the width-depth ratios of the gullies are calculated and analyzed. It is considered that the stability of the loess gullies is poor in the revine developing stage but fine in the clough developing stage, and it can be quantized by the width-depth ratios of the loess gullies. It is forecasted that the unstable period of the loess gullies, i. e. the serious soil erosion period, will be lasted for several hundred thousand years in the loess hill region in the future.