近50年来王茂沟流域侵蚀沟变化及其影响因素

Changes and Influencing Factors of Erosion Gully in Wangmaogou Watershed in the Last 50 Years

基于1968年、2004年和2018年3期高分遥感影像,以王茂沟流域为典型研究区,提取了3个时间点的沟沿线、土地利用、水土保持措施、植被覆盖度和LS因子,对近50年侵蚀沟时空变化特征及其影响因素进行了分析。结果表明:(1)用遥感方法采集的信息,可基本满足侵蚀沟中长期变化分析;(2)50年来王茂沟流域侵蚀沟一直处于变化中,时间上变化速度逐渐减缓,前期和后期沟头年均前进速率分别为0.30,0.27m/a,沟壁年均扩张速率分别为0.009,0.004 m/a;空间上2个时期年均侵蚀沟变化密度大于200 m/(km^2·a)的值分别占比26.89%,7.07%,且多分布在流域中下游;(3)1968—2004年侵蚀沟变化主要受到土地利用变化和水土保持措施增加的影响,2005—2018年,侵蚀沟变化主要受到植被覆盖度进一步提高和土地利用多样性的影响。研究有助于量化分析多年治理过程中侵蚀沟的变化及其影响因素,能对退耕还林还草工程实施前后侵蚀沟治理的生态效益评价提供重要参考。

The spatiotemporal variations and influencing factors of erosion gully in the last 50 years in Wangmaogou Watershed were studied by extracting some information like shoulder line,land use,soil and water conservation measures,vegetation coverage and LS from the three high-resolution remote sensing images of 1968,2004 and 2018.The results showed that:(1)The information collected by remote sensing could basically satisfy the analysis of medium and long-term change in the erosion gully.(2)Gully erosion in Wangmaogou Watershed was developing all the time,but this change tempered gradually in the past 50 years.Specifically,the average advance rate of gully head were 0.30 m/a and 0.27 m/a respectively in early stage and the late stage,and the average expansion rate of gully wall were 0.009 m/a and 0.004 m/a.Spatially,the proportion of the variation density of erosion gully above 200 m/(km^2·a)in the two periods were 26.89%and 7.07%respectively,which mainly distributed in the middle and lower reaches of the watershed.(3)In 1968—2004,the dominant factors affecting the development of erosion gully were land use changes and increased soil and water conservation measures,while erosion gully changes were mainly affected by the further improvement of vegetation coverage and land use diversity in 2005—2018.The study could help to quantify and analyze the development of erosion gully and its influencing factors for many years in the management process,and could also provide an important reference for ecological benefit evaluation of erosion gully before and after the implementation of"Grain-for-Green Program".