黄河中游冻融侵蚀的表现方式及其产沙能力评估

Characteristics of Freeze and Thaw Weathering and Its Contribution to Sediment Yield in Middle Yellow River Basin

黄河中游,尤其是以黄土丘陵沟壑区为代表的那些多沙区的侵蚀产沙是引起黄河下游河道严重淤积的主要原因。在这些地区,水力侵蚀、风力侵蚀、冻融侵蚀是其主要的外侵蚀因素。其中水力侵蚀已经得到比较深入的研究,风力侵蚀也已引起人们的空前重视,而对该区的冻融侵蚀的关注却相对薄弱。实际上,冻融侵蚀对这些地区沟道的作用非常显著。从黄河中游丘陵沟壑区冻融侵蚀的环境背景、作用机理和表现方式等方面展开论述,并根据沟道的岩性特点、沟道侵蚀量大小及对一些实测资料对比,初步认为砒沙岩区的冻融侵蚀量可以达到沟道产沙量的一半左右,最大可达流域侵蚀量的1/3左右。

Sediment yield and delivery in the middle reaches of the Yellow River basin, especially at the loess hill and gully areas, is a primary cause of rapid bed accretion at the lower reaches of the Yellow River. Water flow, wind and freeze and thaw weathering are the important external erosion forces contributing to sediment yield and delivery. Of these three factors, freeze and thaw weathering has not received adequate attention from researchers, given the magnitude of its contributing effects. The environmental background, action mechanisms and representative modes of freeze and thaw weathering occurring in the loess hill and gully areas of the middle Yellow River basin are described and discussed. The sediment yield generated by freeze and thaw weathering in the sandstone area is about 1/2 the sediment yield generated by gully erosion in the area and 1/3 of the total sediment yield of stream catchments, with variations depending on gully lithology, gully sediment yield and other measured data.