Volume estimation of small scale debris flows based on observations of topographic changes using airborne LiDAR DEMs

This paper describes a geographic information system(GIS)-based method for observing changes in topography caused by the initiation, transport, and deposition of debris flows using highresolution light detection and ranging(LiDAR) digital elevation models(DEMs) obtained before and after the debris flow events. The paper also describes a method for estimating the volume of debris flows using the differences between the LiDAR DEMs. The relative and absolute positioning accuracies of the LiDAR DEMs were evaluated using a real-time precise global navigation satellite system(GNSS) positioning method. In addition, longitudinal and cross-sectional profiles of the study area were constructed to determine the topographic changes caused by the debris flows. The volume of the debris flows was estimated based on the difference between the LiDAR DEMs. The accuracies of the relative and absolute positioning of the two LiDAR DEMs were determined to be ±10 cm and ±11 cm RMSE, respectively, which demonstrates the efficiency of the method for determining topographic changes at an scale equivalent to that of field investigations. Based on the topographic changes, the volume of the debris flows in the study area was estimated to be 3747 m3, which is comparable with the volume estimated based on the data from field investigations.     

Damming of large river by debris flow: Dynamic process and particle composition

The frequency and extent of debris flows have increased tremendously due to the extreme weather and the Wenchuan earthquake on May 12, 2008. Previous studies focused on the debris flow from gullies damming the mountain streams. In this paper, an equation for the run-out distance of debris flow in the main river is proposed based on the dynamic equation of debris flow at different slopes given by Takahashi. By undertaking field investigations and flume experiments, a new calculation method of the volume of debris flow damming large river is obtained. Using the percolation theory and the renormalization group theory it was deduced that the large particles should comprise more than 50% for forming a stable debris flow dam. Hence, the criteria of damming large river by debris flow is presented in terms of run-out distance and grain composition which was then validated through the event of damming river by debris flow at Gaojia gully, the upper reaches of the Minjiang River, Sichuan, China, on July 3, 2011.     

Fine root distribution pattern of different aged Leucaena leucocephala trees in debris flow source area in Jiangjia Gully,China

Fine root is critical to restrain soil erosion and its distribution pattern is of great influence on the restraining effects. This study studied the fine root biomass(Br) distribution of different aged Leucaena leucocephala(5, 10, 15 years) in debris flow source area in Jiangjia Gully by digging downward to the bottom at different distances to stem in three directions on slope. The results showed the Br increased dramatically by 143% from 5 years to 10 years and then rose slowly by 38% from 10 years to 15 years. The Br of 5 years was significantly asymmetric between uphill and alonghill directions, but there was little difference among directions for other ages, and a concentration trend appeared to exist in downhill and alonghill directions. Moreover, fine root(D≤1 mm) was significantly heavier than that of fine root(1mmD≤2 mm), playing a leading role in the vertical distribution of the whole fine root, with a logarithmic or an exponential function. The results presented may shed light on fine root distribution pattern and evaluation of its effect on slope stability in debris flow source area.     

莱芜市主要地质灾害特征易发区划分及防治措施

该文总结了莱芜市地质灾害的总体特征,同时具体分析了各种地质灾害的类型、地理分布和主要影响因素等个体特征。以截至2012底的数据为依据,采用地质灾害综合危险性指数法,对莱芜市地质灾害易发程度进行综合分区评价,划定了莱芜市地质灾害高易发区、中易发区、低易发区和不易发区,针对不同的地质灾害种类提出了相应的防治措施。     

群孔抽水试验在新疆哈密大南湖矿区烧变岩层中的应用研究

新疆哈密大南湖矿区北露天煤矿首采区东南部需要揭露Ⅲ火烧岩区一部分,这使得烧变岩水成为露天煤矿矿井充水的主要水源。资源勘探阶段的水文地质资料表明,烧变岩区赋水空间发育、透水能力强,储存量非常可观,但由于受资源勘探阶段水文地质勘探工程量制约,水文地质条件未能详细查明。因此为达到查明烧变岩地下水水力联系、水质变化情况,充分暴露Ⅲ火烧区烧变岩的水文地质条件的目的,设计了该次群孔抽水试验。该次试验查明了烧变岩含水层的水文地质条件,为烧变岩地质条件下防治水工作提供了依据。综合分析表明Ⅲ火烧区烧变岩为储存量型含水层,其补给条件差。     

江西省入境旅游流时空演变研究

采用旅游流年际变动指数、年际集中指数、地理集中指数、基尼系数及空间重心模型,对2000年至2012年江西入境旅游流时空动态演变进行分析。结果表明:1入境旅游流年际波动较大,港澳客源市场表现最为稳定,其次是台湾和外国客源市场,港澳台近程入境旅游客源市场仍具有重要的开发价值,外国入境客源市场潜力还要进一步激发。2年际集中指数较高的美日韩等国,应在稳定基数效应的基础上,加强针对性营销;年际集中指数较低的新加坡、法国、俄罗斯等国,应进行重点开发,培育新兴市场。3港澳游客地理集中度高,外国游客呈现分散-集中趋势,为分散风险应加大对亚洲邻国市场的开拓力度;而城市入境旅游流空间分布相对均衡,客源结构更加完善,但由于交通、区位、资源禀赋、知名度及其客源国消费结构和水平等因素的影响,旅游流重心移动轨迹存在空间错位。     

城市元胞自动机扩展邻域效应的测量与校准研究

城市元胞模型由于在定量分析与预测城市动态的潜力而受到众多研究者的持续关注.邻域规则是主导城市元胞模型模拟过程的关键组件.研究表明,不同土地利用组合间存在显著的邻域效应,且邻域效应具有惯性、排斥和吸引等影响.然而,传统城市元胞模型主要考虑的是特定分辨率下较小窗口的邻域范围.本文尝试刻画更大窗口的邻域效应及其对元胞模型的影响.基于测量的扩展邻域因子,应用粒子群优化算法校准大窗口邻域规则,并创建了考虑扩展邻域效应的城市元胞模型.为验证模型有效性,将其应用于模拟厦门市1995-2010年期间的城市扩张动态.与3×3摩尔邻域的逻辑回归模型相比较,1995-2010年期间的建设用地模拟精度从80.7％提高到83.9％,总体精度从87.8％提高到89.6％,Kappa系数从70.0％提高到74.5％,表明考虑扩展邻域效应的城市模型取得了更好的模拟效果.     

重力模型参数空间差异研究——以中国城市间铁路客流为例

重力模型是重要的空间相互作用模型,已经在相关研究和实践中得到了广泛应用.在重力模型应用中,结果对参数的敏感性较高,不同的参数设置就可能导致结果体系的巨大差异,故精确的参数是重力模型应用的基础.许多研究关注了重力模型参数的提取,但限于数据等因素,参数在空间上的差异性尚未得到充分的重视.本文采用2010年城市间铁路客运量作为城市间相互作用强度的反映,以城市市辖区居民总可支配收入作为城市的“质量”,刻画城市本身的吸引力,进而通过回归分析考察重力模型的参数结果;并结合地理信息系统的空间插值工具,分析重力模型中各个参数的空间差异并得到可视化结果.相比于既有研究,本文在变量选取中增加了城市间列车交流频次这一变量,与平均运行时间结合共同反映城市之间的“距离”,使模型拟合结果得到较大改进.结果表明,重力模型参数取值在空间上存在显著差异,对不同区域使用统一的重力模型参数可能使结果出现较大偏差,因此将重力模型应用到具体实践中时,不能忽略参数的空间异质性.     

泥石流源区典型草本植物根系抗拉试验

植被对于泥石流源区的生态修复和物源稳定具有重要意义,其中植物根系的抗拉力学特性是影响植物护坡的主要因素之一。为了探究泥石流源区植物根系的抗拉特性,以都江堰市锅圈岩泥石流源区为研究区,在野外调查的基础上,通过重要值计算确定了源区典型草本植物并进行抗拉强度试验。研究表明,锅圈岩泥石流源区主要分布有寒芒、节节草等对恶劣环境适应性强的乡土植物,它们的根系平均分布深度在30 cm以内;根系抗拉力与根径呈幂函数正相关关系,抗拉力随根径的增大而增大。当根径0.50 mm时,抗拉强度与根径也表现出幂函数关系;当根径0.50 mm时,部分植物根系的抗拉强度值波动较大。不同植物根系的平均抗拉强度从大到小依次为铁杆蒿(106.24 MPa)、节节草(非节点处,30.79 MPa)、草地早熟禾(28.69 MPa)、小飞蓬(20.20 MPa)、多头苦荬(18.77 MPa)、寒芒(老根,14.87 MPa)、节节草(节点处,12.67 MPa)、寒芒(新根,8.29 MPa)。泥石流源区草本植物的根系抗拉力学特性良好,对稳固浅层土体和泥石流物源有积极作用。     

岷江上游“7·10”泥石流对公路的危害方式及成因

2013-07-10,岷江上游暴发大型群发性泥石流灾害,泥石流以淘刷、冲击、淤塞、压顶、磨蚀等方式对地震灾区公路直接造成严重破坏,其引发的溃决洪水、河床上升增大受灾范围,加重了灾害损失。分析了泥石流对道路工程的成灾方式:对桥梁工程破坏包括淤塞、淘蚀基础、冲毁等;对路面路基工程破坏包括淤埋、淘刷路基、冲毁等;对隧道工程破坏包括堵塞隧道洞口,破坏洞口墙体并引起衬砌支护结构破坏,损毁隧道内附属设施等;对明洞、棚洞工程破坏包括堵塞洞口、冲毁洞口结构,磨蚀洞顶,压顶并引起衬砌支护结构破坏,损毁排水、通风、电力附属设施等。分析了泥石流造成道路严重损失的原因,其中,公路工程选址不当、风险估计不足,桥涵过流净空不足,泥石流防灾措施不完善,泥石流的严重冲刷、冲击作用是主要原因。针对泥石流危害公路的特征和地震区泥石流防治中存在问题,提出了地震山区公路在灾后重建与道路规划中的减灾措施。