黄土高原丘陵沟壑区小流域浅沟和切沟侵蚀区的界定

验证了国外发生浅沟侵蚀和切沟侵蚀判定式在黄土丘陵区的适用性。通过GPS实测数据并结合GIS空间分析与统计回归方法,建立了适用于黄土高原丘陵区的发生浅沟侵蚀和切沟侵蚀判定式。研究结果表明,在黄土高原丘陵沟壑区,随着坡度的增大,发生浅沟侵蚀和切沟侵蚀的临界值a增大,高强度降雨致使判定式中汇水面积（A）的指数b值减小,从而降低了汇水面积的影响作用。在假定其它因素相同时,浅沟形成只需较小的汇水面积,而切沟形成则需要相对较大的汇水面积;当单位汇水面积相同时,发生切沟侵蚀比浅沟侵蚀需要更大的坡度。利用国外研究结果预测提取的浅沟侵蚀和切沟侵蚀发生区,明显夸大了研究区的沟蚀发生区;而用作者所建立的判定式提取的浅沟和切沟侵蚀分布区与野外实际相当吻合。即浅沟侵蚀主要发生在15°～35°的沟间地上,其分布面积占整个沟间地面积的60％,切沟侵蚀主要发生在大于35°的沟坡地上,其分布面积占整个沟坡面积的93％。     

子午岭地区林地破坏加速侵蚀对土壤养分流失和微生物的影响研究

以浅沟集水区为研究对象,分析了子午岭地区林地被开垦破坏15年后裸露地在不同侵蚀强度和侵蚀方式下的土壤养分流失和土壤微生物数量的变化。结果表明,林地开垦破坏后,土壤侵蚀加剧发展,侵蚀强度达159.7t/(hm2a),是林地土壤侵蚀量的上千倍。开垦破坏15年后,裸露地浅沟集水区不同地形部位表层土壤全氮、有机碳、速效磷和土壤微生物总数显著减少,同林地相比,依次分别减少37.9%～82.6%、42.7%～86.4%、24.2%～80.3%和31.8%～92.0%。在裸露地浅沟集水区梁坡随坡长的增加,表层土壤有机碳、全氮和速效磷含量及微生物总数呈显著的下降趋势,且沟槽的土壤各养分含量及微生物总数明显低于沟间。裸露地浅沟集水区土壤养分流失强度及微生物数量减少幅度在浅沟集水区的空间分布与土壤侵蚀方式和侵蚀强度相对应。林地开垦破坏15年后,土壤养分以有机碳流失最严重,其次分别为速效磷、全氮;微生物中的真菌减少幅度最大,细菌次之,放线菌减少幅度最小。     

东北漫岗黑土区地形因子对浅沟侵蚀的影响分析

浅沟侵蚀是坡耕地上重要的产沙方式之一,地形是控制其发生及发展的关键因素。通过对东北漫岗黑土区两个小流域的地形因子和浅沟侵蚀进行相关分析发现,浅沟长度、侵蚀体积与坡面长度呈显著相关,与汇水面积也有较好的相关。根据地形临界理论,确定了研究区浅沟和切沟侵蚀发生的地形临界（S-A）关系：SEG=0.052AEG^- 0.148和SG=0.072 AG^- 0.141,可以用来预测小流域内可能发生浅沟侵蚀以及浅沟向切沟侵蚀转变的部位。在地形分析的基础上,建立了预测浅沟长度的回归模型,交叉验证表明模型对单条浅沟长度的预测误差较大,平均误差37%;而预测浅沟总长度效果较好,预测浅沟总侵蚀量与实测值的误差也只有6%。     

植被破坏与恢复对坡面浅沟侵蚀影响的研究

运用野外实测资料,分析研究了子午岭林区植被破坏与恢复对坡面浅沟侵蚀的影响。所得结论为:一旦植被恢复,坡面浅沟沟槽部位发生泥沙淤积,其淤积速度为0.5cm/a;浅沟沟槽部位淤积,坡面横向起伏减少,坡面向平直方向发展。人为破坏植被后的开垦地,坡面浅沟侵蚀急剧发展,浅沟侵蚀量为4400～7600t/（km²·a）,占坡面侵蚀量的47%以上;当年新冲刷的浅沟沟槽宽为20～80cm,深度为10～30cm;开垦3年裸露地与林地相比,浅沟沟槽深度增加40～60cm;浅沟沟头前进速度为3～5m/a,浅沟深、宽、长的逐年发展,坡面横向起伏加大,片蚀和细沟侵蚀随之加大,又促使了浅沟侵蚀的加剧。     

黄土丘陵区小流域分布式水文和侵蚀模型建立和模拟

基于黄土丘陵区复杂地理环境和土壤侵蚀物理过程,建立了水文过程和侵蚀过程数学模型,水文过程包括降雨入渗和产汇流计算模型;侵蚀过程包括溅蚀-片蚀带侵蚀子模型、梁坡中上部细沟侵蚀带侵蚀子模型、梁坡中下部细沟-浅沟侵蚀带侵蚀子模型、切沟侵蚀带侵蚀子模型、沟道侵蚀带侵蚀子模型;选择黄土丘陵区黑矾沟小流域10场侵蚀性降雨事件作为参数率定,其径流量和侵蚀量模拟精度分别达到了81.8%和70.8%;纸坊沟小流域2场侵蚀性降雨事件用来对模型进行检验,其径流量和侵蚀量模拟精度分别达到了75%和69.3%,与实测结果基本符合,较好地反映了小流域的地表径流过程和侵蚀产沙过程。     

基于RS和GIS的黄土丘陵沟壑区浅沟侵蚀地形特征研究

为了解黄土高原浅沟侵蚀地形特征,基于Qucickbird高分辨率遥感影像和数字高程模型,提取了坡面浅沟及其地形参数,并对浅沟侵蚀的地形特征参数和分布规律进行了统计分析,结果表明：黄土丘陵沟壑区,坡面坡度、长度、坡向以及上坡长度是影响坡面浅沟数量的主要地形要素,而浅沟侵蚀地形特征主要由坡面坡度、坡面长度、上坡长度和汇流面积共同决定;坡面长度与浅沟平均长度呈显著线性关系,坡面坡度与浅沟频度、浅沟坡度与其上坡长度间则均满足二次曲线;发生浅沟侵蚀的上限与下限临界坡度分别介于26～27°和15～20°,临界坡长介于50～80 m;由浅沟坡度的正弦值与汇流面积确定出浅沟分布的临界曲线;阳向坡面的平均浅沟长度小于阴向坡面。基于RS和GIS技术能有效确定浅沟侵蚀地形特征,为黄土区坡面水土流失治理提供了技术支撑。     

定西于家山黄土洞穴的分布特征与侵蚀临界研究

黄土洞穴与滑坡、沟蚀等侵蚀过程联系紧密并加剧了黄土高原的水土流失程度,但目前黄土洞穴发育的分布特征与侵蚀临界暂未明晰。利用无人机获得了研究区高分辨率影像与数字表面模型,基于影像标识了黄土洞穴并统计了其土地利用类型与洞穴直径,利用标识点在数字表面模型上提取了黄土洞穴的坡度、坡向、曲率和汇水面积等地形数据并分析了黄土洞穴的分布特征。结果表明,黄土洞穴直径大多4 m。黄土洞穴在耕地上发育较少,多发育于牧草地区域流水汇聚的凹形坡,且在阴坡更为发育。同时,黄土洞穴坡度正切值范围集中于0.4～1.0,汇水面积一般不超过3 000 m~2。依托统计的坡度正切值与汇水面积数据绘制了黄土洞穴的侵蚀临界图并对比了黄土洞穴与浅沟、切沟的侵蚀临界。黄土洞穴的侵蚀临界边界分别为SA~(0.150)=0.368与SA~(0.135)=7.580,分布较广且覆盖了浅沟与切沟的侵蚀临界。浅沟、切沟的演化与黄土洞穴的发育有关,黄土洞穴通过连通与坍塌促进了浅沟、切沟的发育、转换与扩展,并因此加剧了黄土高原的水土流失。研究量化了黄土洞穴发育的分布特征,建立了黄土洞穴与浅沟、切沟的联系并深化了对黄土洞穴侵蚀过程的认识。     

东北漫岗黑土区防护林带分布对浅沟侵蚀的影响

东北漫岗黑土区坡耕地浅沟侵蚀非常严重,防护林带体系作为坡耕地的重要组成部分,势必会对浅沟侵蚀过程产生影响。本文以漫岗黑土区黑龙江鹤山农场典型小流域为研究对象,基于Quickbird高精度遥感影像和数字高程模型,结合实地调查结果,对小流域内防护林带的分布规律和浅沟侵蚀规律进行了分析,并探讨了防护林带布局对坡面浅沟侵蚀的影响。结果表明:在横坡耕作的坡面上,临界汇水区范围内林带的个数与临界坡长、临界汇水面积呈显著正相关,即增加林带个数、减小林带间距可以增大临界坡长和临界汇水面积,而研究区防护林带间距过大,大于该区浅沟发生的临界坡长,并且防护林带间断有利于浅沟的发育;同时,坡耕地垄向由于受到防护林带影响而与其走向一致,使垄沟笔直穿过低洼水线,形成局部顺坡垄,间接诱发浅沟侵蚀。因此,通过增加横坡耕作坡面上防护林带个数、缩小林带间距、加强林带的管护和更新,同时对不合理的防护林带进行必要的调整,才能有效防治坡面浅沟侵蚀。     

林地开垦后坡沟侵蚀产沙关系的研究

利用在子午岭林区布设的林地开垦后全梁坡、全沟坡（不接收上万来水）和全坡面径流小区，研究了子午岭林区林地开垦后坡沟侵蚀产沙关系。结果表明，子午岭林区林地开垦后，沟坟接收上方来水来沙的侵蚀产沙量是沟坡不接收上方米水来沙侵蚀产沙量的１．９５～３．９倍；全坡面侵蚀产沙在梁坡来水来沙的影响下，侵蚀产沙量增加１０％～３５％；沟坡侵蚀产沙量占总侵蚀产沙量的５３％左右，但其中有２０％的侵蚀产沙量是由于粱坡坡面径流下沟造成的，故受人类活动强烈影响的梁坡，实质上造成了６８％左右的侵蚀产沙量。     

浅沟侵蚀过程及预报模型研究进展

浅沟是黄土丘陵沟壑区的重要产沙方式之一，是在径流冲刷和人类耕作共同作用下形成的。介绍了浅沟侵蚀发生发展过程、浅沟水流水力学特性、浅沟侵蚀影响因素、浅沟侵蚀预报模型等进展，提出了今后亟待加强的研究领域，包括浅沟发生的临界动力条件、浅沟发育过程的定量描述、浅沟水流的剥离方程及泥沙搬运能力、动态监测浅沟侵蚀过程的新方法、包括浅沟侵蚀的坡面土壤流失预报模型等。     

Characteristics and factors controlling the development of ephemeral gullies in cultivated catchments of black soil region, Northeast China

Ephemeral gully erosion is an important process in the black soil region, Northeast China and can be responsible for severe damage to agricultural lands. However, little research on gully formation in this area has been published. The study described in this paper attempted to quantify soil losses, the spatial distribution and morphology of the gullies, and the factors that control their development. Ephemeral gullies were measured in spring and summer of 2005 in two small catchments. The critical periods for ephemeral gully formation were late spring and summer in the study area. Mean soil losses due to ephemeral gully erosion were 0.40 and 0.43 kg m⁻² year⁻¹ for only croplands despite low slope gradients, and this loss is above the tolerable erosion rates of 0.20 kg m⁻² year⁻¹. The erosion rates were greater in spring because the topsoil thawed before deeper layers, reducing infiltration into the soil, and the bare vegetation cover provided no barriers to surface flow. In contrast, summer erosion occurred primarily in response to intense rain events. Development of the gullies was promoted by freeze-thaw cycles in spring and was affected by the type of agricultural operations and crops in summer. A linear regression model for the prediction of ephemeral gully length at the catchment level was established using field data, and although it did not successfully predict the length of individual gullies, it explained 55% of the variation in ephemeral gully length.     

黄土丘陵沟壑区浅沟水流水动力学参数实验研究

浅沟侵蚀是黄土丘陵沟壑区重要的侵蚀类型,浅沟水流的水动力学参数研究是建立浅沟侵蚀物理模型或概念模型的基础。以黄土丘陵沟壑区延安市燕儿沟小流域的坡地为对象,通过野外放水冲刷实验,对浅沟水流的水动力学参数变化特征进行研究。结果表明：浅沟水流属于紊流范围,大多数情况下是急流;在坡度18°左右时,携沙水流的流速最小,阻力最大,此时水流的能量分配在侵蚀与携沙之间达到平衡;浅沟水流在坡度26°左右时流速达到最大,水流功率达到最大,最利于浅沟侵蚀的发生和发展。研究结果可为黄土区浅沟侵蚀物理模型的建立提供理论支撑。     

Study of ephemeral gully erosion in a small upland catchment on the Inner-Mongolian Plateau

Ephemeral gully erosion is an important soil erosion process on the Inner-Mongolia Plateau in North China, and although its damage is very intense, little research on the area has been published. In this paper, a global positioning system (GPS) is used to measure the morphology of ephemeral gullies in a small catchment, the Inner-Mongolia Autonomous Region. First, this paper presents the characteristics of ephemeral gullies and soil loss due to ephemeral gully erosion. The network of ephemeral gullies takes on the shapes of tree branches, and there are 16 hole-ephemeral gullies in the middle of the ephemeral gullies. An average gully length of about 19.6 m ha⁻¹ and an average soil loss of 8.8 m³ ha⁻¹ due to ephemeral gully erosion were measured. Second, soil erosion influences crop production in cropland and combinations of vegetation in fallow. The difference between vegetation in the middle of ephemeral gullies and in other places is very obvious. Third, this paper discusses hole-ephemeral gullies that are holes locating in the middle of ephemeral gullies whose widths and depths are more than 0.5 m (Fig. 6) for the first time. The relationship between local hill slope gradient S (m m⁻¹) and upslope contributing area A (ha) can be expressed as S = 0.064A^−0.375 and may be a key indicator for determining the position of existing hole-ephemeral gully heads and for predicting where hole-ephemeral gullies could form in the small watershed on the Inner-Mongolian Plateau.     

Application of the EGEM model to predict ephemeral gully erosion in Sicily,Italy

Recent research has shown the importance of ephemeral gully (EG) erosion in the context of global erosion and, at the same time, the lack of adequate models to estimate it. At present, the ephemeral gully erosion model (EGEM) is the only conceptual model specifically developed for ephemeral gully erosion estimation. The main aim of the paper is to evaluate the performance of EGEM model adapted to local conditions compared with that of simple empirical equations. A data set of 92 ephemeral gullies formed between 1995 and 2000 in a wheat-cultivated study area in Sicily, Italy, was used for the purpose. In order to improve EGEM performance, two important adaptations were made. Both the rain distribution type and the causative rainfall of the hydrological component of EGEM were modified to reproduce local conditions. The EGEM assumption of a constant depth for the entire length of the ephemeral gully was also modified. EGEM performance was tested with two different rain distribution types, three different causative rainfalls and two different EG depths. The adaptation of the EGEM hydrological component improves the volume prediction with respect to the standard version of EGEM; the improvement is mainly due to the rain distribution type, whereas causative rainfall seems to be less important. The use of adjusted EG depths is, however, essential to minimise the errors between measured and predicted volumes. The capability of EGEM to predict the ephemeral gully cross-section is weak and non-significant relationships were found between measured and estimated width. A regression analysis between ephemeral gully-eroded volume and different morphological, topographical and hydrological parameters confirms the great importance of EG length to explain eroded volume (R²=0.64 for the simple correlation between volume and length). Considering that the adaptation of the hydrological component and the measurement of EG depths are necessary for the EG volumes estimated by EGEM to be reliable, it seems more simple, as suggested by other authors, to use empirical relations between eroded volume and length performed in different environments, until more precise physically based models are developed.     

Ephemeral gully recognition and accuracy evaluation using deep learning in the hilly and gully region of the Loess Plateau in China

Ephemeral gullies are widely distributed in the hilly and gully region of the Loess Plateau and play a unique role in the slope gully erosion system. Rapid and accurate identification of ephemeral gullies impacts the distribution law and development trend of soil erosion on the Loess Plateau. Deep learning algorithms can quickly and accurately process large data samples that recognize ephemeral gullies from remote sensing images. Here, we investigated ephemeral gullies in the Zhoutungou watershed in the hilly and gully region of the Loess Plateau in China using satellite and unmanned aerial vehicle images and combined a deep learning image semantic segmentation model to realize automatic recognition and feature extraction. Using Accuracy, Precision, Recall, F1value, and AUC, we compared the ephemeral gully recognition results and accuracy evaluation of U-Net, R2U-Net, and SegNet image semantic segmentation models. The SegNet model was ranked first, followed by the R2U-Net and U-Net models, for ephemeral gully recognition in the hilly and gully region of the Loess Plateau. The ephemeral gully length and width between predicted and measured values had RMSE values of 6.78 m and 0.50 m, respectively, indicating that the model has an excellent recognition effect. This study identified a fast and accurate method for ephemeral gully recognition in the hilly and gully region of the Loess Plateau based on remote sensing images to provide an academic reference and practical guidance for soil erosion monitoring and slope and gully management in the Loess Plateau region.