Early Holocene High Magnitude Debris Flow Events and Environmental Change as Illustrated by the Moxi Platform, Hengduan Mountains, SW China

Thick debris flow deposits in the Hengduan Mountains of southwestern China record landscape instability at the close of the last glaciation and in the early Holocene. The deposits, ranging in thickness from 100 to 200 m, are common and in high magnitude in the valleys of this region. They are products of large debris flows induced by glacier and enabled by the presence of large amount of glacial debris on the landscape. The carbon 14 dating from Moxi Platform indicates that a period of catastrophic debris flows occurred at c. 7 kyr B.P., and was concurrent with other glacial-fluvial fans and terraces which tied to regional climatic oscillations elsewhere in the Himalaya. The comparable events suggest a strong climatic control on earth surface processes for the dynamics, magnitude, and frequency in this region.

Variations in tidal currents and suspended sediment concentration of the upper part of the North Channel of Changjiang Estuary over the past 10 years

The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the North Channel of Changjiang Estuary. They were assimilated with the measured data in 2003, 2004, 2006 and 2007, using the tidal range＇s proportion conversion. Variations in TCD and TCV, preferential flow and SSC have been calculated. Influences of typical engineering projects such as Qingcaosha fresh water reservoir, Yangtze River Bridge, and land reclamation on the ebb and flood TCD, TCV and SSC in the North Channel for the last 10 years are discussed. The results show that： （1） currently, in the upper part of North Channel, the ebb tide dominates; after the construction of the typical projects, ebb TCD and TCV tends to be larger and the vertical average ebb and flood SSC decrease during the flood season while SSC increases during the dry season; （2） changes in the vertical average TCV are mainly contributed by seasonal runoff variation during the flood season, which is larger in the flood season than that in the dry season; the controlling parameters of increasing ebb TCD and TCV are those large-scale engineering projects in the North Channel; variation in SSC may result mainly from the reduction of basin annual sediment loads, large-scale nearshore projects and so on.

Analysis on Suspended Sediment Deposition Rate for Muddy Coast of Reclaimed Land

A new expression for calculating suspended fine-sediment deposition rate is developed based on theoretic analysis and experiments. The resulting equation is applied to simulation of fine sediment deposition in the reclaimed land in the Hangzhou Bay, China. The hydrodynamic environment in this area is solved by use of a long wave model, which gives the 2D-velocity field and considers bathymetric changes due to fine sediment deposition. The expression is proved convenient to use in engineering practice, and the predicted deposition rate agrees with the annual data available from field measurements from the first year to the third year after the construction of the long groin as a reclaiming method.

Seabed deposition and erosion change and influence factors in the Yangshan Deepwater Port over the years

The seabed scouring and silting are very important to the construction of port and waterway engineering. Seabed deposition and erosion change is complicated due to the influence of sediment supply, human activities and other factors. The Yangshan Deepwater Port is the new deep water harbor, which is an important part of the Shanghai International Shipping Service Center. Its construction has received much attention. At present, the water depth from the 1 st to the 3 rd harbor district is currently suitable under regular dredging and tidal current action. The fourth harbor district will be built in the world’s largest fully-automated deep water wharf. In the study, bathymetry change of the entire sea area of the Yangshan Deepwater Port and the 4 th harbor district(i.e.,Phase IV project) waters were analyzed quantitatively using multiyear bathymetric, hydrological and sediment data. The results show that from 1998 to 2010, seabed changes are characterized by large volumes of erosion and sedimentation, which the southern part was deposited and the northern part was eroded in the inner harbor waters, but the seabed of the Kezhushan inlet was eroded. Seabed changes of Phase IV project waters generally show a scour tendency in recent few years with the annual scour rate about 0.7 m. Among the many factors, the existence of Kezhushan inlet and its influence of the western water flow play an important positive role in water depth changes under the ebb tide action.

基于FLOW-3D的尾矿库逐渐溃坝三维数值模拟

为了分析尾矿库逐渐溃坝时溃口随时间的变化过程以及溃坝后尾砂的淹没范围,基于FLOW 3D软件建立了三维数值模型。模拟了水槽内的逐渐溃坝,将计算得出的溃口形态变化数据以及水位数据与实验数据进行对比,结果基本吻合,验证了数值模拟的精确性和可靠性。以某尾矿库为例,利用该数值模型模拟逐渐溃坝,结果表明:尾矿坝溃决时先冲刷溃口底部,而后逐渐向两侧侵蚀,坝体侵蚀断面呈U型分布,随着水量减少,泥沙慢慢沉积,最终稳定,泥沙下泄量约为总泥沙量的31.1%,随着距离的推移,泥沙淤积量沿程减少,下游房屋监测点最大水深15.44 m。

FLOW STRUCTURE AND SEDIMENT TRANSPORT WITH IMPACTS OF AQUATIC VEGETATION

Aquatic vegetation plays an important role in the flow structure of open channels and thus changes the fate and the transport of sediment. This article proposes a three-dimensional turbulence model by introducing vegetation density and drag force into the control equations of water flow in the presence of vegetation. The model was used to calculate the impacts of submerged vegetation on the vertical profiles of longitudinal flow velocities, the changes of the depth-averaged flow velocities in a compound channel with emergent vegetation in the floodplain, the removal of suspended sediment from the channels by emergent vegetation, and the bed changes around and in a vegetated island. Numerical investigations show that aquatic vegetation retards flow in the vegetation zone, reduces the sediment transport capacity, and contributes to erosion on both sides of the vegetated island. Calculated results agree well with experimental results.

On the Unusual Holocene Carbonate Sediment in Lake Nam Co,Central Tibet

In lacustrine sediments,aragonite is a widespread mineral,whereas monohydrocalcite is a rare carbonate mineral. In the cold and high-attitude Xizang (Tibetan) Plateau,where aragonite has been commonly found in lacustrine sediments,there is no aragonite,but low-Mg calcite,monohydrocalcite and trace dolomite. The lake receives solutes primarily from surface runoffs and remains fairly constant water chemistry for a long time. The total CaCO3 percentage in sediments could be controlled by evaporation and inflow of detrital materials. The absence of aragonite is unusual when compared to other lacustrine sediments from the Tibetan Plateau. This could be due to low Ca/Mg ratio,low salinity,low Mg and Ca concentration. Monohydrocalcite might precipitate from the lake water mediated by biological activities. Low-Mg calcite originated from minor ostracoda shell and the precipitation of lake water with biological activities.

Application of numerical model in evaluating the effects of a planned reservoir on reach-scale bankfull discharge of the lower Wei River

Predicting the responses of an alluvial channel to changes in flow and sediment supply is essential for engineering design. Many methods have been developed in the last few decades to describe sectional bankfull characteristics(elevation and discharge); however, studies on long-term reach-scale bankfull discharge are still limited. In this study, a hydraulic model is built to calculate the reach-scale bankfull discharge, and the effects of reservoir building on downstream bankfull discharges are discussed. The studied river reach is located at the lower Wei River(WR), where the planned Dongzhuang Reservoir would be built on its largest tributary, the Jing River. A quasi-two-dimensional numerical model coupled with a bankfull discharge estimating method is put forward to calculate the reach-scale bankfull discharge. The soundness of the model is verified. Results show that the temporal variation of reach-scale bankfull discharge of the lower reach of the WR would be highly influenced by the planned reservoir, especially during the first 20 years of operation. The effect of the planned reservoir on bankfull discharge may reach its maximum when the total trapped sediment load reaches approximately 75% of the reservoir capacity. Our results show that after the first 17 years of operation,the effect of the planned reservoir on bankfull discharge of the river reach may decrease gradually.The soundness and predictive capability of the coupled model have also been calibrated by comparing with existing reservoirs. All analyses indicate that the numerical model can be used to predict the changed reach-scale bankfull discharge of the lower WR.

Middle-late Holocene environment change induced by climate and human based on multi-proxy records from the middle and lower reaches of Yangtze River,eastern China

Our knowledge about the interaction between human activities and the environment in the middle-late Holocene remains incomplete.Core C1 in Lake Chaohu from the middle and lower reaches of Yangtze River (MLYR),eastern China,provides an opportunity to investigate vegetation and climate changes,human activities,and East Asian summer monsoon(EASM) evolution since 5100 cal.yr BP.These variables are assessed based on radiocarbon dating,pollen and charcoal records,and magnetic susceptibility (χ_(lf)),median grain size and TP.Results reveal a hiatus in sedimentation between 2080 and 730 cal.yr BP in the western part of Lake Chaohu,which is common in most lakes in the MLYR.Evergreen and deciduous broadleaved mixed forest retreated gradually after 3650 cal.yr BP,and was replaced by secondary Pinus forest after at least 730 cal.yr BP.Intense agricultural activities and vegetation clearance are first detected at 2520 cal.yr BP.Human settlements expanded from the lake front wetlands (during the period 2520–2080 cal.yr BP) to remote high-altitude areas(2080–400 cal.yr BP),and then returned to the lake front to reclaim the wetlands and lake (after 400 cal.yr BP).A gradual trend of recessional EASM strength from 4300 cal.yr BP and centennial-scale variations of EASM during the period5100–3650 cal.yr BP are revealed.The reduction of summer insolation,southward shift of the ITCZ,and El Ni?o Southern Oscillation may control the intensity of EASM and climate on a large regional scale.

Environmental and biogeo- chemical process of accumula- tion of iron-phosphorus in marine sediments

This paper discusses the environmental and biogeochemical process of accumulation of iron-phosphorus in marine sediments for the north aktian of the South China Sea and analyzes the relationships between the contents of iron, phosphorus and calcium carbonate as well as their ex-istent characteristics. The results show that the variances of phosphorus and calcium carbonate contents with depths are opposite and those of iron and calcium carbonate contents are almost accordant. It is not only related to the biogeo-chemical process of accumulation of biogenous calcium car-bonate in sediments, which resulted from the fact that the marine primary productivity was stimulated by part of ter-rigenous phosphorus dissolved into seawater due to decline of superficial water temperature and increase of carbon di-oxide content in the glacial period, but also related to iron impelled oxidation and accelerated deposit by the dissolved oxygen from the atmosphere and the photosynthesis of hy-drophytes in seawater. The variance of soluble iron-phos- phorus species (Fe-P) in sediment columns can sensitively reflect the changes of climate and environment, which sug-gests that the accumulative characteristics and existent states of iron-phosphorus species (Fe-P) in marine sediments have the significance as an indicator of the changes of paleocli-mate and paleoenvironment.

陆相坳陷湖盆深水重力流沉积类型、模式及控制因素分析——以鄂尔多斯盆地延长组长7段为例

鄂尔多斯盆地长7深水沉积是大型坳陷湖盆深水重力流的典型代表。基于多口取心井厘米级岩心描述和测录井、薄片资料,对长7深水重力流沉积的类型、特征、流体性质和沉积演化过程进行探索。明确深水沉积包括4种类型:深湖泥页岩沉积、滑塌沉积、砂质碎屑流沉积、浊流沉积。剖面上三角洲前缘砂体在外力触发条件下发生滑塌,转变为砂质碎屑流,最终演化为浊流。平面上三角洲前缘坡折带末端发育大面积砂质碎屑流舌状体,其前端的浊流沉积呈扇状分布。鄂尔多斯盆地晚三叠世独特的构造背景、气候条件以及强烈的造山活动,造就了鄂尔多斯盆地特有的重力流沉积模式。砂质碎屑流和浊流砂体分别对应长7页岩油的一类、二类砂体,具有近源成藏的优势,油气资源量可观,目前已产生规模效益。

鄂尔多斯盆地东南部三叠系长7油层组深水沉积特征及演化规律

以沉积学理论为指导,利用野外露头、钻井岩心、测井等资料,对鄂尔多斯盆地东南部三叠系长7油层组深水沉积特征包括相标志、沉积微相类型等进行了研究,并揭示了其沉积演化规律。研究结果表明:(1)鄂尔多斯盆地东南部三叠系长7油层组深水沉积的相标志包括:岩石中常见水平层理、鲍马序列、槽模沟模、滑动与滑塌构造、撕裂屑、泥包砾等沉积构造,含有深水双壳类和鱼类动物化石,粒度概率曲线中悬浮总体含量大且分选差,测井曲线上可见锯齿状、齿化箱形-钟形-指形、泥岩基线等特征。(2)研究区长7物源主要来自东北和南部2个方向,发育深湖—半深湖、湖底扇、浅湖沉积,湖底扇包括浊流和砂质碎屑流2种重力流类型,可进一步划分为重力流主水道、溢流沉积、重力流分支水道、分支水道间、朵叶体等微相。湖底扇主水道主要为砂质碎屑流沉积,分支水道和朵叶体主要为浊流沉积。(3)研究区长7沉积期,中南部主体发育深湖—半深湖、湖底扇沉积,东北部发育浅湖沉积;其中,东北方向发育4个湖底扇体,南部发育2个湖底扇体,半深湖/浅湖界线呈北西向延伸于延安—甘泉一带。长7^(3)亚段沉积期,深湖—半深湖范围最大,仅局部发育湖底扇;长7^(2)、长7^(1)亚段沉积期,湖底扇逐步增多,深湖—半深湖范围有所缩小,整体呈深湖—半深湖与湖底扇交互沉积态势。

风景园林美感探究——景的人境感应机制与景境回路设计原理

围绕风景园林美感的研究对象、个体与群体、文化与科学、误区与症结、研究战略、如何创新突破等问题,以“景”为主线,揭示风景园林美感成因与机制的流变性,构建景境回路设计原理。分别从哲学、人居环境学、风景园林学三方面展开,构建景的“人-境互动”模型,剖析景作为风景园林美感的源头、成因、机制作用,揭示景的“人-境互动”流变机制。为此,分析论述了景与园、与意境的关系,提出“经”的概念。进一步阐明了建筑学非生命美学与风景园林生命美学的根本差别及因偏离了基于生命美学的风景园林美学分析评价的基本方向性误导,主张以风景园林的过程动态感受主导风景园林美感评价,指出流变性这一风景园林美感美学的内在属性,提出以“景流”作为评价风景园林美感的准则和标准,并为风景园林美感流变理论奠定基础。具体成果如下:1)提出了“风景园林美感流变理论”雏形;2)发展中国传统八景理论,提出了主观、客观、主客观结合的“3类八景”24位元素及其8条风景园林美感规划设计的流变线索;3)基于美感流变理论,构建了由回路、景境、景阻、景势、景流组成的“景境回路设计原理”。

合水地区长6_(3)深水重力流沉积特征研究

合水地区是鄂尔多斯盆地近年来原油勘探的重点区块,在系统分析沉积构造、岩石学特征、结构粒度特征等沉积相识别标志的基础上,结合区域沉积背景,开展了合水地区长6_(3)重力流沉积类型及展布特征研究。结果表明,合水地区长6_(3)油层亚组为湖泊-重力流沉积体系,发育半深湖-深湖沉积亚相,可进一步划分为浊流沉积、砂质碎屑流、滑塌沉积三种重力流沉积类型;其中砂质碎屑流及浊流为主要控砂微相,主要分布在研究区的中部、南部区域,为区内有利储集相带。

Paleosol evolution and environmental change in the Huang-Huai-Hai Plain, China

Paleosols in the Huang-Huai-Hai Plain occur mainly in the Huaibei, Xuhuai, Yischuheand Jiaolai areas. They result from 3 sedimentation-soil formation cycles since the LatePleistocene. Each cycle left calcareous concretions, a dark soil horizon, and a topsoil horizonand/or a stratified soil horizon all derived from loess. This paper examines the composition of theconcretions, compares this with that of the enclosing soil horizons, and draws some environmentalconclusions. Three types occur: embryonic calcareous concretions, mature calcareous concretions,and calcareous hardpans （petrocalcic horizons）. The embryonic concretions formed during themid-Holocene （6780±130 yr. B.P.）, mature calcareous concretions during the late-Pleistocene（weighted average of 31 samples = 15670±370 yr. B.P.）, and calcareous hardpans （petrocalcichorizons） from 16 to 40 ka B.P. The calcium carbonate content increases from 412 g/kg in theembryonic concretions, to 551 g/kg in the mature concretions, and to 691 g/kg in the hardpan,whereas contents of SiO2, Al2O3 and TiO2 decrease accordingly. Spore pollen analysis shows thatthe late-Pleistocene there was dry and cool, whereas the mid-Holocene was warm and humid andlakes were more extensive than today.

面向输沙过程模拟的改进流向算法

流域中的输沙过程是地貌学和地表动力学的重要研究内容。前人通过流向算法和实测地形变化来推测输沙率的空间分布,但是简单地应用流向算法会造成模拟过程中出现质量不守恒的情况。因此,设计了面向输沙过程模拟的改进流向算法,判断模拟过程中质量守恒情况,即输沙率是否为负值,若存在,则将负值输沙率重设,阻止负值输沙率向下游传播。对经典的D8、MFD-se、MFD-md 3种流向算法进行了改进实验。结果表明:(1)改进后的D8单流向算法相较于改进前的性能平均提升了1.26%。(2)改进后的MFD-se单流向算法相较于改进前的性能平均提升了4.17%。(3)改进后的MFD-md单流向算法相较于改进前的性能平均提升了4.54%。

三峡水库蓄水后长江中游嘉鱼河段河床演变特性分析

嘉鱼河段是长江中游典型的碍航河段之一,需重点关注河床演变特性。根据1970~2021年实测水下地形资料,全面分析了该河段的冲淤、岸线、河床形态、洲滩深槽等变化,研究该河段自2003年三峡水库蓄水运用及2006年实施航道整治工程以来河床演变特性。结果表明:自三峡水库蓄水运用以来,该河段岸线基本稳定,河床冲刷部位主要在枯水河槽;近些年断面形态逐渐趋于稳定,岸线变化不大;河段内洲滩平面位置保持相对稳定的状态,仅在复兴洲尾部左缘、燕窝镇对面江中形成了一个新的江心洲;深槽平面位置较为稳定。研究成果可为该河段防洪调度、河道治理等提供参考。

黄土丘陵区生态恢复重建过程中流域降雨及其水沙变化特征研究

以燕沟流域为研究对象,着重研究生态恢复重建过程中流域系统的降雨和水沙变化特征,并对高度治理流域的总体减沙水平做了分析。结果表明:治理流域增强了土壤接受降雨的入渗能力,提高了流域自身林草涵养水分以及流域地表对径流的调蓄能力,因而增加了流域生态建设可用的径流资源量。燕沟流域1997年以来的年降雨量具有一定的代表性,说明燕沟流域的输沙模数逐年锐减,对近年来流域所实施生态环境建设和流域植被重建工程起到了显著的水土保持效果,与治理前相比,减沙效益约为83.7%。

近2600年来内蒙古居延海湖泊沉积物的色素含量及环境意义

通过分析东居延海S1探坑剖面色素含量 ,结合碳酸盐、介形类化石、腐殖酸、磁化率及化学元素等多环境指标分析结果 ,探讨该区近 2 6 0 0年来环境气候波动特点。研究区气候变化大致经历几个阶段 :温暖湿润(2 6 5 0～ 2 5 6 0aB .P .)→湖泊菱缩 ,气候偏干暖 (2 5 6 0～ 2 36 0aB .P .)→暖湿气候背景下湖泊的扩张 (2 36 0～2 1 2 0aB .P .)→冷湿向冷干转换 ,湖泊由大湖开始菱缩 (2 1 2 0～ 1 6 0 0aB .P .)→气候暖湿 ,湖泊再次扩张 ,(1 6 0 0～ 6 5 0aB .P .)→湖泊由扩张到菱缩 ,气候由冷湿向暖干变化 (6 5 0aB .P .—至今 )。同时尝试把色素与其它指标的结合作为指示湖泊古初始生产力的有效性 。

青藏高原东北边缘泥石流发生与沉积史初探

文章对青藏高原东北边缘的古泥石流发生历史进行了分析 .研究表明 :古泥石流主要发生于 3 0～ 3 5Ma,2 4～ 2 5Ma ,1 9～ 1 6Ma ,1 0～ 1 1Ma ,0 7～ 0 9Ma ,0 6Ma,0 33Ma ,0 1～ 0 14Ma以及全新世 .泥石流是气候变化和构造运动的共同产物 ,随着晚上新世以来青藏高原及周围山地在一系列构造运动影响下逐步隆升 ,导致地形反差加大 ,气候冷暖变化频繁 ,泥石流爆发的频率加大 .人类活动只能加剧泥石流的爆发 ,却不能从根本上阻止它的发生 .随着全球变暖 ,有可能出现一些灾害性的气候变化 ,这必然会导致中国西部泥石流的发生频率和规模有所加大 .