Effect of coir geotextile and geocell on ephemeral gully erosion in the Mollisol region of Northeast China

The unique geomorphological features and farming methods in the Mollisol region of Northeast China increase water catchment flow and aggravate the erosion of ephemeral gully(EG).Vegetation suffers from rain erosion and damage during the growth stage,which brings serious problems to the restoration of grass in the early stage.Therefore,effects of coir geotextile and geocell on EG erosion under four confluence intensities were researched in this study.Results of the simulated water discharge erosion test showed that when the confluence strength was less than 30 L/min,geocell and coir geotextile had a good effect on controlling EG erosion,and sediment yield of geocell and coir geotextile was reduced by 25.95%–37.82%and 73.73%–88.96%,respectively.However,when confluence intensity increased to 40 L/min,protective effect of coir geotextile decreased,and sediment yield rate increased sharply by 189.03%.When confluence intensity increased to 50 L/min,the protective effect of coir geotextile was lost.On the other hand,geocell showed that the greater the flow rate,the better the protective effect.In addition,with the increase in confluence intensity,erosion pattern of coir geotextile developed from sheet erosion to intermittent fall and then to completion of main rill,and the protective effect was gradually weakened.In contrast,the protective effect of EG under geocell was gradually enhanced from the continuous rill to the intermittent rill and finally to the intermittent fall.This study shows that coir geotextile and geocell can prevent EG erosion,and the effect of geocell is better than that of coir geotextile on the surface of EG.

Spatiotemporal variations in ecosystem services and their trade-offs and synergies against the background of the gully control and land consolidation project on the Loess Plateau,China

Studying the spatiotemporal variations in ecosystem services and their interrelationships on the Loess Plateau against the background of the gully control and land consolidation(GCLC)project has significant implications for ecological protection and quality development of the Yellow River Basin.Therefore,in this study,we took Yan'an City,Shaanxi Province of China,as the study area,selected four typical ecosystem services,including soil conservation service,water yield service,carbon storage service,and habitat quality service,and quantitatively evaluated the spatiotemporal variation characteristics and trade-offs and synergies of ecosystem services from 2010 to 2018 using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.We also analysed the relationship between the GCLC project and regional ecosystem service changes in various regions(including 1 city,2 districts,and 10 counties)of Yan'an City and proposed a coordinated development strategy between the GCLC project and the ecological environment.The results showed that,from 2010 to 2018,soil conservation service decreased by 7.76%,while the other three ecosystem services changed relatively little,with water yield service increasing by 0.56% and carbon storage service and habitat quality service decreasing by 0.16% and 0.14%,respectively.The ecological environment of Yan'an City developed in a balanced way between 2010 and 2018,and the four ecosystem services showed synergistic relationships,among which the synergistic relationships between soil conservation service and water yield service and between carbon storage service and habitat quality service were significant.The GCLC project had a negative impact on the ecosystem services of Yan'an City,and the impact on carbon storage service was more significant.This study provides a theoretical basis for the scientific evaluation of the ecological benefits of the GCLC project and the realization of a win-win situation between food security and ecological security.

Analysis of debris flow control effect and hazard assessment in Xinqiao Gully,Wenchuan M_(s)8.0 earthquake area based on numerical simulation

Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.

Characteristics of gully bed scour and siltation between check dams

Check dams are the most commonly used engineering measure for debris flow control worldwide.The scour and siltation characteristics between dams are important factors affecting dam design.In this study,classical dimensional analysis of the variables that influence the development of gully bed scour and siltation was carried out.Flume experiments were conducted to examine the influence characteristics of opening width,flume slope,debris flow density,and opening rate on the characteristics of gully bed scour and siltation.The influential characteristics of variables on the dimensionless scour depth,scour length,siltation length,scour volume and siltation volume were obtained.The experiments showed that,with an increase in the relative opening from 1.5 to 2.5,scour depth increased by 7.4%,scour length decreased by 11.2%,siltation length increased by 22.0%,scour volume decreased by 4.7%and siltation volume increased by 22.0%.With an increase in flume gradient from 0.105 to 0.213,scour depth,siltation length and siltation volume increased by 40.0%,65.9%and 65.9%,respectively,and scour length decreased by 20.1%.With an increase in sediment concentration from 0.303 to 0.545,siltation length and siltation volume increased by 15.4%and 15.4%,respectively,and scour depth,scour length and scour volume decreased by 9.6%,9.1%and 17.8%,respectively.As opening rate increased from 0.08 to 0.32,siltation length and siltation volume increased by 33.3%and 33.3%,respectively,and scour depth,scour length and scour volume decreased by 5.4%,13.7%and 18.4%,respectively.The results showed that the flume gradient was the most influential factor on scour depth,scour length,siltation length and siltation volume,and the sediment concentration was the most influential factor on scour volume.Then,according to the experimental data,some empirical formulas predicting scour depth,scour length,siltation length,scour volume and siltation volume were obtained.The error between the computed values according to the formulas in this paper and the observed values was within±10%.These research results may provide a technological basis for window dam design in debris flow disaster prevention and mitigation.

A novel gully network extraction method combining hydrological confluence process and surface morphology

The automatic extraction of gullies from digital elevation models(DEMs)has great application value in GIS and hydrology.Many types of algorithms have been developed to address this problem,and the well-known D8(Deterministic eight-node)algorithm has been widely applied and implemented in some commercial GIS software such as ArcGIS.However,a key parameter called flow accumulation threshold(FAT)must be determined in this process.Numerous studies focus on how to determine an optimal value for this parameter but ignore that the optimal threshold varies for different gullies,so the universality of a different optimal threshold parameter determined by different methods is poor.To address this problem,this study designs a parameter called surface concavity index(SC-index)that can describe the shape of gullies from the perspective of surface morphology.Based on this index,the positions of different gullies'heads are identified,and then the flow accumulation matrix calculated by the D8 algorithm is used as auxiliary data to extract the gully network in the research area.In this study,six small watersheds in the Loess Plateau in northern Shaanxi,China,were used as test areas to verify the validity of the proposed method in areas with various landform types.Experimental results show that gully heads in different test areas can be effectively identified by setting different SCindex thresholds that are related to the types of terrain in the test areas.Then,the entire gully network can be extracted in watersheds with the help of a D8 algorithm.The accuracy of the gully network extracted by the new method is better than the contrast method in all test areas.In test areas with a large area of flat land(e.g.,Chunhua),the difference between the total length of gullies extracted by the new method and the reference value is-2.77 km,while the corresponding value of the contrast method is 14.50 km.In test areas with large numbers of short gullies(e.g.,Jiuyuangou),the difference between the total length of gullies extracted by the new method and the reference value is-2.61 km while the corresponding value of the contrast method is-27.9km.It is pointed out that the new method can not only avoid the extraction of pseudo gullies,but also extract short gullies effectively.Further experimental analysis shows that the dependence of the new method on DEM resolution is significantly weaker than that of the contrast method.Taking Jiuyuangou test area as an example,when the DEM cell size increases from 5 m to 30 m,the total length of gullies extracted by the new method changes only about 1km,while the corresponding value of the contrast method exceeds 20 km.

Regional differences in gully network connectivity based on graph theory:a case study on the Loess Plateau,China

Material exchange frequently occurs in gullies,and thus the relationship between a gullynetwork structure and sediment transport potential has attracted considerable interest.However,previous researches ignored the difficulty of material transport from sources to sinks,and did not quantify the connectivity of a network structure.In this study,we used a graph model structure to model gully networks of six typical sample areas in the Loess Plateau of China and quantified gully network connectivity using four indexes:average node strength,accessibility from sources to sinks,potential flow,and network structural connectivity index.Results show that:(1)Reflected by different quantitative indexes,the trends of gully network connectivity in different regions are similar.From north to south,the connectivity of a sample area first increases and then decreases.(2)The more mature gullies have stronger network connectivity.Small resistance is conducive to material transport in the gullies.(3)The node connectivity index of the gully network shows a significant aggregation distribution in space,and node connectivity on the main channel is often stronger than that on the branch trench.These results not only deepen the understanding of the process and mechanism of loess gully geomorphic development and evolution but also provide a reference for geomorphic studies.

Evolution of gully erosion and susceptibility factors in the urban watershed of the Kimemi(Butembo/DR Congo)

Gully erosion is one of the most intense landscape degradation mechanisms in areas with varying environmental characteristics.Both natural and anthropogenic factors affect the gullying process.Reliable documentation of these processes in tropical African cities is scarce.This study assessed the gully erosion dynamic and the sus-ceptibility factors in the urban watershed of Kimemi in eastern Democratic Republic of Congo(DRC).Data were obtained through a combination of fieldwork and digitization of very high spatial resolution images from Google Earth(from 2011 to 2021).The length,width,and area of large gullies(width≥5 m)were measured for each year of the study.A logistic regression model(LRM)was also used to investigate the influence of both physical and anthropogenic factors on gully susceptibility.The results revealed that the number of gullies has increased from 36 to 61 during the last decade.The gully mean length of 63.9±61.1 m,129.3±104.9 m,and 174.7±153.8 m were obtained for the years 2011,2015,and 2021 respectively.The average density of gully network for the study period was 0.12 km/km^(2),while the degraded land was -1.3 and -1.1 ha/year for 2011-2015 and 2015-2021 for the entire watershed.The significant changes in morphometric parameters(length,width,area)were found only in the bare land and building land uses.A strong and positive relationship between the length(m)and the area(ha)was found.Furthermore,the susceptibility of gullying was significantly influenced by the slope,stream power index(SPI),distance to roads and rivers,land use and land cover(LULC),and normalized difference vegetation index(NDVI).This means the areas located in the bare land and building or close to roads and/or streams are more likely to be gullied.The findings emphasize the impact of urbanization on gully erosion in the Kimemi watershed,highlighting the importance of informed land management decisions with a close attention to anthropogenic factors.

2023年积石山Ms6.2级地震同震地质灾害初步分析

2023年12月18日,甘肃省临夏回族自治州积石山县发生Ms6.2级地震,触发了大量同震地质灾害,亟需查明同震地质灾害的基本特征、发育分布规律和成因机制,为震后恢复重建与地质灾害防治提供支撑。本文基于多源高分辨率遥感解译和已有研究成果对比分析,初步揭示了此次地震地质灾害的基本特征和发育分布规律,并探讨了草滩村液化滑坡—泥流的成因机制。结果表明:此次地震Ⅶ度及以上烈度区内共发育1 535处同震地质灾害,主要为中小规模黄土滑坡和浅表层岩质崩塌,集中分布于黄土梁和黄土塬内冲沟两侧、单薄黄土梁两侧以及大型历史滑坡后壁等局部地形较陡峭的部位。地震因素控制了同震地质灾害的区域分布规律,而地形因素控制了同震地质灾害的局部分布规律。同震地质灾害在0.1~0.3 g震峰值加速度区域、发震断层下盘区域、南东坡向、30~60 m坡高范围、斜坡中部以上20~40 m范围分布数量最多。受广泛关注的草滩村“砂涌”灾害本质是饱水黄土在地震作用下发生的液化滑坡。2016年完成的填沟造地工程改变了滑源区地表和地下水流通条件,地下水通道被堵塞,导致地下水位抬升和下部土体饱和可能是该处发生液化滑坡的重要原因。

富水沟谷区浅埋煤层导水裂隙演化特征

富水沟谷区域下浅埋煤层赋存条件特殊,采场上覆岩层导水裂隙发育演化特征复杂。为了揭示沟谷区浅埋煤层在回采扰动作用下覆岩裂隙演化规律,以朱家峁煤矿1305-2工作面过沟谷区回采阶段为工程背景,采用理论分析、物理相似模拟、数值模拟与现场效果验证的方法,建立了覆岩裂隙−渗流场概念模型,开展了覆岩结构发育与微震能量演化研究,分析了覆岩变形与塑性破坏分布特征,提出了针对沟谷区下浅埋煤层导水裂隙防治措施,并应用于现场工程实践。结果表明:开采扰动下裂隙−渗流场模型呈“梯台”结构,并依次划分为初渗区域、稳渗区域、紊渗区域3个区域;将所研究矿井的工况数据代入模型结构,计算出各个渗透区域范围,并根据计算结果对矿井的稳渗区域采取注浆措施。工作面回采至沟谷区段,覆岩裂隙域形态呈现“拱形-梯形-复合梯形”的扩展演化特征,裂隙纵向发育高度达到163 m,并与沟谷区地表贯通。随工作面推进,地表裂隙依次经历“滑移-挤压-撕裂”过程;沟谷区域位移云图呈现出滞后开采“高位梯形”破断形态,在沟底处下沉位移最大,达3.47 m。针对开采导致的裂隙大范围扩展贯通,提出在地面进行采动裂缝注浆处理,在工作面上覆岩层进行注浆封堵,实现过沟谷区开采“井上−井下”联合防治,保证安全开采。该研究结果可为浅埋煤层的过沟谷区开采、采动裂隙防治及富水区“保水采煤”提供新的科学依据。

罗玉沟流域水沙变化趋势及影响因素

[目的]探讨小流域水沙变化趋势及影响因素,为黄土高原丘陵沟壑区水土流失治理和水土保持措施布设提供参考依据。[方法]采取Spearman秩次相关检验方法、累积距平法和双累积曲线法等对黄土丘陵沟壑区罗玉沟流域1986—2016年降水量、径流量和输沙量变化趋势和演变过程进行分析。[结果](1) 1986—2016年罗玉沟流域年降水量趋势性变化不显著;流域年径流量和年输沙量变化具有明显的阶段性,以1993年为界,年径流量和年输沙量呈显著降低趋势。(2)降水和水土保持措施影响罗玉沟流域年径流量和输沙量,不同降水水平年,降水和水土保持措施对流域水沙变化的影响不同,水土保持措施使流域枯水年份径流量和输沙量减少最为显著。(3)水土保持措施对年径流量和年输沙量的减少贡献率分别为83.50%和80.97%。[结论]降水量变化不显著的情况下,水土保持措施对罗玉沟流域年径流量和年输沙量的减少起主导作用,水土保持综合治理对枯水年径流量和输沙量的影响幅度最大。

黄土高原河谷城镇“川—沟”融合单元发展路径研究

通过分析黄土高原河谷城镇独特的城乡关系与发展困境,认为川道与次沟空间结构一体化、功能结构差异化发展是振兴黄土高原丘陵沟壑区的重要突破口,由此提出“川—沟”融合单元的概念内涵与划定方法。以榆林市绥德县为例,打破镇域行政边界和小流域镇村体系,基于川道城镇和次沟乡镇的空间关联关系划定10个融合单元,并从用地形态结构、产业经济地理、服务设施配置等方面对融合单元的空间构型、功能类型和服务水平进行剖析,探讨川道与次沟协同视角下以融合单元为抓手推动黄土高原河谷城镇高效发展和管控治理的新路径。

基于HEC-HMS的黄土高塬沟壑区流域城市化对洪水情势的影响

黄土高塬沟壑区城市化过程中下垫面硬化会影响暴雨水文情势,增大洪水模拟预报难度。为实现对流域城市洪水灾害的预警,基于HEC-HMS水文模型,分别率定砚瓦川流域城市化前后不同时期土地利用条件下的产汇流参数,开展极端暴雨洪水情景设计,揭示流域城市化对不同重现期洪水的水文效应。结果表明:建立的HEC-HMS降雨-径流模型适用于黄土高塬沟壑区洪水预报,其模拟综合合格率为81.25%,平均Nash效率系数为0.82;流域城市化对重现期短的洪水要素变化影响较大,且洪量变化幅度大于洪峰变化幅度,100 a一遇洪水的洪峰和洪量的增幅分别为4.54%和6.40%,5 a一遇洪水的洪峰和洪量的增幅分别为7.06%和9.49%;各子流域设计洪水对流域城市化的响应分布具有空间差异性,以西北部地区响应为最强,其次为南部地区,东北部地区最弱。

浅埋煤层过沟开采覆岩破坏特征及水害防治技术研究

黄土沟壑区溃水水害是浅埋煤层开采的主要灾害之一。安山煤矿煤层埋藏浅、局部沟道所在区域5-2煤层顶板距离地表不足30 m,为了解决黄土沟壑区工作面过沟开采可能遇到的水害问题,通过数值模拟的手段研究了工作面过沟开采时的覆岩破坏特征,提出了研究区过沟开采时冒裂安全性分区标准,并基于分区结果提出了预防工作面过沟开采发生溃水水害事故的防治技术,过沟开采防治技术包括采前筑坝截流引流,采后工作面地表裂缝修复等,并在工作面过沟开采区域成功地进行了防治应用,应用结果表明,防治技术能够有效预防工作面过沟开采溃水水害。研究成果对榆神矿区工作面安全、绿色高效过沟开采具有一定的借鉴意义。

东北黑土区沟蚀研究进展与热点——基于CiteSpace计量分析

[目的]直观把握东北黑土区沟蚀研究进展与热点,推进东北黑土区沟蚀研究领域的发展。[方法]以CNKI与Web of Siencec数据库中245篇相关文献为对象,利用文献计量的方法,使用CiteSacep软件绘制东北黑土区沟蚀研究知识图谱。[结果]结果表明:(1)黑土区沟蚀研究起步较晚,近十年发文量显著增加,但国际期刊发表成果较少,仅占26%。(2)该领域研究力量主要分布在我国东北,其中水利部松辽流域委员会、北京师范大学、中国科学院东北地理与农业生态研究所、东北农业大学、沈阳农业大学等机构贡献突出、影响较大;张树文是该领域中文发文量最多的学者,刘宝元和伍永秋是英文发文量最多的学者。(3)关键词共现表明,目前对东北黑土区沟蚀的关注重点主要集中在侵蚀沟发育特征、影响因素和沟蚀防治措施等方面。[结论]东北黑土区沟蚀尚未形成完整的研究框架和全面的认识,在未来的研究中,需进一步注重东北黑土区沟蚀形成和发育过程及机理研究,并深入分析地质、地形、水文、人类活动等因素的影响。

基于统计学模型的沟道侵蚀敏感性评估的研究进展与展望

侵蚀沟的发生通常会造成区域严重的环境破坏和经济损失。开展沟道侵蚀敏感性评估有助于相关部门采取合理有效的措施抑制并降低沟蚀的发生,对改善区域环境、维持粮食生产能力,保障经济健康发展具有重要意义。该文从沟道侵蚀敏感性评估流程、数据基础以及统计学模型的应用3个方面,系统地介绍了该方向的研究进程,列举了各分类下统计学模型的优缺点,分析了该方向的相关研究进展,对比了不同研究之间的应用条件,并指出,未来研究还需实现迁移学习和时间序列模型在沟道侵蚀敏感性评估中的应用,以及深度学习模型与侵蚀沟发育物理机制相互融合,从而为改进和加强统计学模型与沟道侵蚀敏感性评估之间交叉应用,推动土壤侵蚀学科发展,为区域发展规划奠定理论与技术基础。

降雨、汇流和坡度对黑土浅沟坡面侵蚀影响的试验研究

[目的]为研究降雨、汇流和坡度对浅沟侵蚀的影响,实施精确的水土保持措施。[方法]通过室内模拟降雨和汇流试验,设计2个降雨强度(50,100 mm/h)和2个坡度(3°,7°),并在4种降雨强度和坡度组合下设置5个依次增加的汇流强度(15,30,45,60,75 L/min),分析降雨、汇流和坡度及其交互作用对浅沟坡面侵蚀的影响,明确浅沟侵蚀对坡面侵蚀的贡献。[结果](1)坡度和汇流强度对浅沟坡面侵蚀的影响均大于降雨强度。当降雨强度由50 mm/h增加到100 mm/h时,3°和7°对应的坡面侵蚀量分别增加52.3%~81.8%和29.4%~88.4%;而当坡度从3°增大到7°,50,100 mm/h降雨强度对应的坡面侵蚀量分别增加114.3%~395.5%和130.0%~320.9%;当汇流强度由15 L/min增加至75 L/min,坡面侵蚀量增加4.6~13.5倍。同时,汇流强度的增加加剧坡度对坡面侵蚀的作用,而减弱降雨强度对坡面侵蚀的影响。(2)降雨、汇流、坡度双因子和三因子交互作用对浅沟坡面侵蚀的影响以汇流强度-坡度交互作用和降雨强度-汇流强度-坡度三者的交互作用的影响最大,其次为降雨强度-汇流强度交互作用,而以降雨强度-坡度的交互作用的影响最小。(3)不同试验条件下,浅沟侵蚀量占坡面侵蚀量的比例平均在85%以上,且其比例随汇流强度和坡度的增加呈增大趋势。(4)坡面侵蚀速率与水流流速、径流剪切力和水流功率之间均表现为极显著正相关,与阻力系数之间呈显著负相关;且坡面侵蚀速率与水流功率相关关系最优。[结论]研究结果为基于侵蚀动力因子和地形因子及其交互作用的浅沟侵蚀预测模型开发、浅沟侵蚀贡献分离和浅沟侵蚀机理研究提供了科学依据。

黄土高原典型流域水蚀因子多重分形特征

[目的]探索高程、坡度、土地利用、植被覆盖度等水蚀因子的空间内部多重分形特征,进而深刻认识黄土高原水蚀机理。[方法]分别以黄土高原沟壑区和黄土丘陵沟壑区的两个典型流域(长武县王东沟流域与淳化县泥河沟流域,米脂县泉家沟流域与安塞县纸坊沟流域)为例,利用多重分形方法计算分析了水蚀因子的多重分形谱及其主要参数,探讨了水蚀因子多重分形特征。[结果]地貌相对起伏最大和土地利用空间不均匀程度最高的是王东沟流域,其坡度与土地利用的奇异指数Δα值分别是0.817,0.310,而植被覆盖区域差异最大的是泉家沟流域,其植被覆盖的Δα=1.309;黄土丘陵沟壑区高程的Δf(α)<0,黄土高原沟壑区坡度的Δα与Δf(α)皆大于丘陵沟壑区,即丘陵沟壑区的相对起伏更大,地貌表面更尖锐,土地利用破碎化更严重,植被覆盖区域间复杂程度高。[结论]王东沟流域的地貌相对起伏程度和土地利用破碎化更大,泉家沟流域的植被覆盖复杂程度最高,与实际情况相符,即在区域开展水蚀因子量化进行多重分形特征分析是可行的。

北洛河上游流域植被覆盖度时空变化及其地形分异特征

[目的]揭示退耕还林还草工程实施前后黄土丘陵沟壑区流域植被恢复过程,阐明流域植被恢复的地形分异效应,进而为黄土丘陵沟壑区制定适宜的流域生态建设和保护对策提供科技支撑。[方法]基于北洛河上游流域1990—2019年4期Landsat影像及数字高程模型数据,利用像元二分模型结合GIS技术,开展了退耕还林还草工程实施前后该流域植被覆盖度变化地形分异特征研究。[结果](1)流域植被覆盖度在空间上呈现东南高、西北低的分异特征。1990—2019年流域年均植被覆盖度呈持续上升趋势,在退耕还林还草工程实施以后高等级植被覆盖度面积占比大幅提升,1990年、2000年、2010年、2019年高等级植被覆盖度面积占比分别为0.97%,6.96%,42.17%,64.18%。(2)在工程实施的各个时期,流域植被覆盖总体持续改善,但西北局部地区植被退化。研究期间,流域植被覆盖度结构改善明显,中高及高植被覆盖度面积以转入为主,中低及低植被覆盖度面积以转出为主。(3)流域植被覆盖度在地形上存在明显分异特征,植被覆盖度随高程的增加呈减小趋势,植被覆盖度与坡度呈正相关,坡度越陡,植被覆盖度越大,植被覆盖度随坡向遵循阴坡>半阴坡>平地>半阳坡>阳坡的分布规律。[结论]实施退耕还林还草工程对增加北洛河上游流域植被覆盖度起到了关键作用,但部分区域植被退化严重,未来该流域应重点关注城市空间扩展以及气候变化对植被建设的影响,以应对环境演变下植被生态系统可持续发展面临的挑战。

大规模沟谷型泥石流成因与减灾启示——以黑水县谷汝沟“7·14”泥石流为例

沟谷型泥石流具有谷坡陡峻、相对高差大、沟道坡度大等特点,往往形成大规模的泥石流灾害。2021年7月14日20时许,黑水县谷汝沟发生大规模泥石流灾害,造成直接经济损失3300万元。为提高和完善泥石流灾害的预测预警手段与减灾水平,以沟谷型泥石流谷汝沟“7·14”泥石流为典型研究对象,通过现场勘察、模型计算、流域地貌信息熵和气象分析等方法,揭示谷汝沟“7·14”泥石流特征,分析其成因,预测其未来发展趋势。结果表明:谷汝沟“7·14”泥石流容重为1.83g/cm3,属于黏性石流,平均流速为11.2m/s,泥石流峰值流量达到991.2 m3/s;流域处于壮年偏幼期的地貌发育阶段,为谷汝沟“7·14”泥石流暴发提供了充足的动力势能条件,49.7mm的日降雨量是泥石流的激发因素;根据灰色灾变预测模型,谷汝沟将在2027年、2034年、2042年暴发泥石流灾害。研究成果有助于完善沟谷型泥石流的预测预警,可为其他地区泥石流防灾减灾提供参考。

泥石流承灾体群体效应特征反演——以7·12四川平武县黑水沟泥石流为例

群体建筑结构的分布格局、结构形式等因素影响泥石流冲击过程和致灾表现。泥石流冲击存在绕流现象、放大作用和遮蔽效应,泥石流与建筑群之间存在复杂的流固耦合模态,但针对这类泥石流承灾体群体效应的过程与机制仍不清晰。本研究通过野外调查、物理实验和数值模拟等方法,调查泥石流承灾体群体效应特征,反演泥石流冲击流场分布和建筑损伤过程,提出了一套建筑群对泥石流的承灾动力响应特征分析方法。研究结果表明:(1)泥石流流场存在放大作用。面对泥石流冲击,建筑群的破坏导致沟道区域流速增加20%,建筑群区域流速增加46%。(2)泥石流流场存在绕流现象。建筑群阻碍泥石流直进输运,导致建筑拐角之间存在局部压力高度集中现象。(3)在建筑群中存在明显的遮蔽效应。失去建筑的上游遮蔽保护可使下游建筑受到的泥石流冲击强度增加120%。(4)泥石流致灾过程中,建筑群周边与内部的泥石流冲击特征差异明显。在建筑群外围,受前排建筑破坏的影响,泥石流流线后排建筑受泥石流冲击时刻提前10 s,泥石流冲击强度增加速率达2.1倍;(5)泥石流对建筑群内建筑冲击强度分为冲击力急剧增加—缓慢增加—逐渐稳定三个阶段,对应泥石流流深增高、缓慢淤积过程。研究结果可以为泥石流易发区村落城镇的建筑规划布局和防灾减灾措施提供科学参考。