Nature and Dynamics of an Active Block Stream, Kunlun Pass, Qinghai Province, People's Republic of China

Active block streams are common on the slopes of mountains on the northern, drier portion of the Qinghai-Xizang (Tibetan) Plateau. Between 1990 and 1995, the authors studied a block stream northeast of the crest of the Kunlun Pass at latitude 35°50’N, longitude 94°05’ E. It occurs on a 31° slope facing southwest at 4800 m altitude and consists of a 15 cm layer of blocks moving downslope over a sandy loam of lacustrine origin. The blocks are derived from both frost shattering of exposed bedrock and by ejection of blocks from the till capping the hill. No water flows in the block stream and its surface is level with the surrounding slope. Mean annual air temperature is –6°C and mean annual precipitation is about 320 mm. The few plants growing between the blocks exhibit elongated stems and/or roots, indicating movement of the upper layers of blocks relative to the underlying materials. Average mean annual downslope movement of the surface blocks ranges up to 95 cm but varies both across the block stream and also along its long axis. The blocks are gradually extending further downslope. Comparison of movement of lines painted on stones in summer and winter shows that most of the movement occurs in winter. The stones usually rotate randomly as they move, probably by sliding on ice. There is no obvious sorting or rounding of the blocks during movement downslope. The deposits produced differ from talus/scree sediments as they have a dip of less than the maximum angle of rest of dry sediment (c. 33°) and also show no sorting downslope. The movement of material takes place predominantly in winter, rather than in summer and the deposits occur in areas of negligible snow cover. Ground temperatures suggest exceptionally rapid temperature changes under the blocks, indicating air exchange in the voids. Mean ground temperatures in the loams beneath the blocks are about 7°C colder than in the adjacent soils. Winter snow covers are noticeably absent, and summer precipitation is often in the form of snow, which soon melts. Permafrost is present beneath the block stream but is absent in the sandy loam soils. The ground is also moister beneath the blocks. It appears that the surface blocks tend to slide downslope on the icy surface of the underlying blocks, perhaps aided by water from melting snow. This and the lack of sorting by clast size clearly differentiates them from talus slopes or avalanche deposits.     

Modelling Spatial Patterns of Overbank Sedimentation on Embanked Floodplains

This paper presents a GIS-based mathematical model for the simulation of floodplain sedimentation. The model comprises two components: (1) the existing hydrodynamic WAQUA model that calculates two-dimensional water flow patterns; and (2) the SEDIFLUX model that calculates deposition of sediment based on a simple mass balance concept with a limited number of model parameters. The models were applied to simulate floodplain sediment deposition over river reaches of several kilometres in length. The SEDIFLUX model has been calibrated and validated using interpolated raster maps of sediment deposition observed after the large magnitude December 1993 flood on the embanked floodplain of the lower river Rhine in the Netherlands. The model appeared to be an adequate tool to predict patterns of sediment deposition as the product of the complex interaction among river discharge and sediment concentration, floodplain topography, and the resulting water flow patterns during various discharge levels. In the investigated areas, the resulting annual average sedimentation rates varied between 0.5 mm/year and 4.0 mm/year. The role of the most important mechanisms governing the spatial patterns of overbank deposition, i.e. inundation frequency, sediment load, floodplain topography and its influence on the flow patterns over the floodplain, are discussed.     

长江宜昌-武汉河段泥沙年冲淤量对水沙变化的响应

运用泥沙收支平衡 (Sediment budget) 的概念确定长江中游宜昌-武汉河段的泥沙冲淤量,并运用数理统计方法,研究了泥沙冲淤过程对水沙变化的响应。研究表明,所研究河段的输沙具有“多来多排”的特性,在平均的意义上,年输入沙量为年输出沙量的1.1345倍,由此求得总净来沙中有11.85%淤积在河道中。河段出口输出沙量随时间而增大,大致在1980年达到峰值,然后再减小。1980年以前河段出口输出沙量的增大,与3口分沙减少 (等价于河段净来沙增多) 和下荆江人工裁弯 (使河道输沙能力增大,因而可以将更多的泥沙输送到河段出口以下) 有关,1980年以后的减少,则与宜昌站来沙量的显著减少有关。建立了1980~1997年间宜昌-汉口#河段年冲淤量与宜昌站年来沙量之间的回归方程,通过该方程估算出使宜昌-汉口河段不淤的宜昌站临界来沙量为3亿t/a。为了定量评价宜昌站的来水量和来沙量以及3口分水比和分沙比、宜昌站洪峰流量的变化对于河段冲淤量的相对贡献,我们以1980~1997年和1955~1997年两个时间系列的数据分别建立了多元回归方程。1980~1997年间的方程表明,宜昌站的来水量和来沙量以及3口分水比和分沙比、宜昌站洪峰流量的变化对宜昌-汉口河段年冲淤量的贡献率分别为6.23%、31.56%、25.77%、32.71%和3.73%。     

长江中下游河床沉积物分布特征

对长江中下游武汉至河口段304处河床沉积物样品进行了粒度测量与分析,通过各参数间的模拟、统计及对比,探讨了沉积物粒度、水动力因素及河床地貌三者间的关系。研究结果表明：本区河床沉积物以中、细砂为主,床底搬运十分微弱,河道相对稳定;从上至下沿程有明显的“粗-细-粗-细”粒径变化,主要反映河流动力地貌、动力沉积特征;粒径在河床的沿程分布总体为北粗南细,说明北岸侵蚀,南岸淤积的特点。研究同时也表明,颗粒因河型不同而迥异;颗粒偏态度-峭度在不同河型中表现各异,对区分顺直微弯分汊和鹅头形分汊河道尤为显著。     

长江中游马口-田家镇河段40年来河道演变

Quantitative analysis was performed on the filling-scouring process for the river reach within Makou and Tianjiazhen, the middle Yangtze River with the help of GIS and DEM techniques. The research results indicate that the river reach between Makou and Tianjiazhen was dominated by the scouring process, and the magnitude of scouring is increasing over time. The intensity of scouring process is more in the deep and narrower river reach than shallower and wider ones. The river reach in the Makou and Tianjiazhen river knot is in fre-quent scouring and filling process, however the river reach upper to the Makou and lower to the Tianjiazhen river knot is in moderate scouring and filling process. The river reach just upstream or downstream to the river knot (e.g. Makou and Tianjiazhen river knot in this research) is dominated by filling process and the river reach in the river knot is dominated by the scouring process. Research results indicate no changes in the boundary of the river but the scouring and the filling magnitude in specific river channel is strong. The filling and the scouring process of the study river reach is greatly impacted by the sediments and water from the upstream of the study river reach. The construction of the Three Gorges Dam just upstream to Yichang will cause further decrease of the release of the sediment load to the middle and the lower Yangtze River basin, which will further intensify the scouring process of the river channel in the study river reach.     

西北江网河来水来沙及分水分沙变化特征

根据西、北江干流高要、石角和西北江网河区顶端马口、三水共4个代表水文站1960-2004年流量、输沙率的月均序列,分析西北江网河来水来沙及分水分沙变化特征,结果表明:西北江网河来水来沙季节变化明显,且西江比北江更为集中;西江的水沙变幅比北江小,西、北江输沙率年际变化大于流量年际变化;来水来沙均存在明显的3种尺度周期变化,即年内(0.3～0.7 a)、年际(1.2～6.6 a)和年代际(11.0～20.2 a)周期变化,以年代际变化最为显著;来水量长期变化趋势除马口站外均为递增,来沙量长期变化趋势除三水站外均为递减;1993年后西北江网河区顶端三水站分流分沙比显著增大,其与网河区大规模无序采沙活动密切相关.     

The role of channel and floodplain storage in the suspended sediment budget of the River Ouse, Yorkshire, UK

This study attempts to quantify the amount of fine-grained (ca. < 150 μm) sediment stored on the floodplains and on the channel bed of the non-tidal sections of the main channels in the catchment of the River Ouse (3315 km²) and of one of its tributaries, the River Waarfe (818 km²), in Yorkshire, UK. Caesium-137 analyses of floodplain sediment cores were used to quantify the amount of Iloodplain deposition as a result of overbank flooding during the last ca. 40 years. A combination of bulk and sectioned cores were collected along transects perpendicular to the channel at 26 sites throughout the study basins. In general, rates of overbank sedimentation decrease with distance from the channel. The average values for individual transects range between 0.010 and 0.554 g cm⁻² year⁻¹. Floodplain storage along the main channels of the Ouse and Wharfe basins accounts for 60645 and 10325 t year⁻¹, respectively, and represents a net loss from the system. The amount of fine-grained sediment stored on the channel bed was estimated by a survey undertaken in August 1996, during which the fine material deposited on the bed was resuspended and its mass estimated at 16 locations. The average values for the individual locations range between 0.017 and 0.924 g cm⁻² and tend to increase downstream. The total channel bed storage at the time of sampling in 1996 was estimated to be 16076 and 1866 t for the Ouse and Wharfe basins, respectively. It is assumed that channel bed storage is seasonal and that no net loss to the system occurs at the annual timescale. Floodplain storage for the Ouse and Wharfe basins represents 39 and 49%, and channel bed storage equals 10 and 9%, respectively, of the annual suspended sediment load (1995–1996) delivered to the channel system. These results have important implications for the routing of fine-grained sediment and sediment-associated contaminants in drainage basins, and for the interpretation of downstream sediment yields in terms of upstream sediment mobilisation.     

三峡水库修建前长江宜昌-武汉段泥沙输移比及其影响因子

运用泥沙收支平衡(Sediment budget)的概念确定长江中游宜昌-武汉河段的泥沙输移比,并运用数理统计方法,研究了1955～1997年间河道泥沙输移比对水沙变化的响应.从总体上看,河道泥沙输移比有较显著的增大趋势.输移比的变化可分为4个阶段:1955～1962年为快速增大;1963～1975年亦为增大,但增速减慢;1976～1979年为迅速减小;1980～1997年为较快增大.在分析了若干水沙指标对河道泥沙输移比的影响的基础上,建立了宜昌-汉口河段泥沙输移比与宜昌站的来水量和来沙量以及3口分水比和分沙比、宜昌站洪峰流量之间的多元回归方程.1980～1997年间的方程表明,宜昌站来水量越多、3口分流比越小,宜昌一汉口河段泥沙输移比越大;宜昌站来沙量越少,3口分沙比越大,泥沙输移比越大;宜昌站洪水流量越大,泥沙输移比越小.     

黄河内蒙古头道拐断面形态变化及其对水沙的响应

根据黄河上游位于弯曲一顺直过渡段的头道拐断面的多年实测水文、泥沙数据和断面资料,分析了断面对上游一系列水利工程在时间尺度上的调整响应过程.结果发现,头道拐断面的形态变化强烈受到上游水库运行的影响,在一系列水库投入运行后,河床粗化现象一直持续到三湖河口断面以下.头道拐断面悬移质泥沙中值粒径在水库运行后表现为先增大,然后减小,最后再增大的三阶段性特征,并且自1986年龙羊峡与青铜峡、刘家峡等水库联合运用以后,该三阶段性特征的变化幅度明显较只有青铜峡、刘家峡水库单独运行时段(1969-1986年)小.另外,自1987年以来,头道拐断面河道的横向摆动速率大幅减小,断面形态及位置趋于稳定,有利于当地百姓正常的生活和生产.     

Relationships between rainfall and landsliding in the Middle Hills,Nepal

Many studies have documented major landslide events in mountain areas following heavy rainfall amounts. In the Himalaya, landslides occur during every monsoon period, but the role of rainfall in triggering these failures is not clear. This paper reports the results of a three-year study (1991-1993) into landsliding in the Likhu Khola drainage basin, Middle Hills, Nepal. Considerable annual variability in numbers, types and sizes of landslides was noted. Some of this variability can be explained by fluctuations in rainfall amounts and intensities, but many landslides were explained more easily by other controlling factors. In situations where slopes are extensively terraced for agriculture, with some terraces being intensely irrigated and others not, relationships between landsliding and rainfall amounts are complex and no simple explanations can be made.     

黄河下游河床纵剖面形态及其地文学意义

本文通过河床比降和凹度两个指标,研究黄河下游河床纵剖面形态的自动调整作用,结果发现比降和下凹度多年平均值分别为1.28和1.35,偏离均值为1～2%,变化很小,说明黄河下游河床纵剖面以近于平行抬升的形态调整,标志着河道已进入了老年期发育阶段。对于研究河道发育史和老年期河道的特点,以及在治河上均有重要的理论和现实意义     

黄河中游降雨特性对泥沙粒径的影响

以黄河中游36个有泥沙粒径资料的水文测站流域为样本，在不同自然地理类型流域划分的基础上，建立了流域泥沙粒径特片与降雨特性的关系。结果表明，在不同类型流域，流域泥沙的粗细与降雨季节性变率和年际变率之间存在着相当好的线性正相关关系；而与年降雨量和降雨不均匀系数之间呈明显的非线性关系。流域地面物质、植被和地貌发育程序等下垫面环境因素对泥沙粒径特性与降雨特性之间关系起着十分重要的控制作用。不同类型流域曲线的斜率各不相同，在图中所处的位置也不相同。     

疏勒河流域泥沙分布规律及水沙关系研究

泥沙是影响河流健康和水环境的重要因素之一,受气候变化和人类活动的影响,流域水文要素和下垫面条件发生了较大变化,尤其是实施大规模的水土保持措施后,部分河流的泥沙含量大幅减少,但在河西内陆河流域发源于祁连山西端的疏勒河流域,受降水条件和人类活动的影响,河流泥沙呈增加趋势。本文应用疏勒河流域实测长系列水文资料,采用水文统计法、差积曲线法、趋势检验法、突变检验法、非线性复相关模型法等方法,分析了流域泥沙时空分布规律及水沙关系,结果表明：疏勒河干流昌马堡站年输沙量为333.5×104 t,至下游潘家庄站减少到223.5×104 t;党河党城湾站年输沙量为76.56×104 t,至下游沙枣园站增加到121.3×104 t;疏勒河干流输沙量主要集中在汛期7～8月,占全年的81.9 %～84.0 %,党河流域输沙量主要集中在4-8月,占全年的92.3 %;流域泥沙变化总体呈增加趋势,突变点1998年以后,年输沙量增加了86.3 %～148.2 %。建立了潘家庄站降水～泥沙、径流～泥沙以及年输沙量～年径流量～年最大洪峰流量关系模型,相关关系较好,相关系数达到0.717～0.858。流域出山口以上对泥沙的影响因素主要是降水,出山口以下主要是修建水库、水电站、引水工程、河道采砂等人类活动影响。随着国家对内陆河流域祁连山和河西走廊的日益关注,以及全国河长制的推行,河流生态健康已经提上日程,研究疏勒河流域泥沙分布规律及水沙关系,对国家实施西部生态安全战略、区域生态环境修复治理、水资源可持续利用等具有重要意义。     

洞庭湖的冲淤变化和空间分布

在实测的1974，1988，1998年1：2.5万地形图的基础上，利用地理信息系统的数据处理和空间分析方法，分析洞庭湖24年来的冲淤规律，得到了2个时期（1974-1988，1988-1998）洞庭湖冲淤量和冲淤区域的空间分布位置，研究表明，洞庭湖近24个来总的趋势冲淤厚度没有明显的变化，为0.017m/a。以两期冲淤变化的趋势预测了2010年三峡工程全部完工时洞庭湖的冲淤变化状况，结果表明，1998-2010年间洞庭湖将平均淤高0.33m。最后以3年数字地形模型为基础，分析了洞庭湖24年来的不同水位下湖盆容积的变化。     

基于遥感与GIS的江河源区土地利用动态变化研究

基于TM／ETM卫星遥感数据,运用GIS方法,对江河源区1986～2000年土地利用类型的时空变化特征进行了研究。结果表明：近15年来源区林地、湿地、草地和冰川面积减少,建设用地、耕地和未利用土地面积显著增加,土地综合利用程度下降。土地利用动态转化过程以草地转化为未利用土地、湿地转化为草地和未利用地逆转为草地为主要特征,全区土地利用的空间位置转换而积大于其数量变化。气候变化和人类经济活动是导致研究区土地利用变化的丰要因素。     

西安北郊渭河河漫滩沉积与洪水事件

根据西安北郊相家巷河漫滩沉积剖面中180个样品的颗粒分析和历史文献资料记载,研究了西安北郊相家巷漫滩沉积代表的洪水事件。研究表明:西安北郊相家巷剖面洪水沉积分层明显,对洪水的发生和短期降水量变化反映清楚。相家巷剖面洪水沉积厚度约为5.40m,可划分为28个层,指示发生了28次大小不同的洪水事件。剖面中的洪水沉积以中、粗砂和细砂为主,指示当时的洪水规模比近120年来关中渭河洪水明显大。这28次洪水事件发生时高漫滩上的洪水深度均大于2.2m,剖面中的第12、14、19~28层代表特大洪水事件。西安北郊相家巷洪水沉积代表的大规模洪水主要是由当年降水量的明显增加引起的。     

Channel braiding and stability of the Brahmaputra River, Bangladesh, since 1967: GIS and remote sensing analyses

Spatial and temporal changes in channel distribution in the large, sandy, braided system of the Brahmaputra River, Bangladesh, were analyzed using satellite images and GIS. Supervised classification of the images within the braided belt, i.e., channels and bars between the bank-lines, provided raster land cover data for 14 different years between 1967 and 2002. The width of the braided-belt, the number and width of channels, the distribution of land cover attributes and land stability change were examined from the data. The results indicate that the recent history of the dynamics of the Brahmaputra can be divided into four phases: 1) the late 1960s to early 1970s, 2) the mid-1970s to early 1980s, 3) the mid-1980s to early 1990s, and 4) the mid-1990s to early 2000s. Spatial distributions of the land cover and channels in Phase 4 were the least complex suggesting a state of dynamic equilibrium. Land cover and channel distributions during Phase 2 were partly less complex indicating quasi-dynamic equilibrium. Phases 1 and 3 can be regarded as transitional phases with more complex conditions. Frequent large floods may have triggered significant changes in the river system during Phases 1 and 3.     

黄河下游游荡段河道平面形态与河热变化趋势预测

黄河下游可道平面形态与河势演变,从２０世纪６０年代起,地貌界就用地图法和航片资料作过不同程度的研究。随着资料的不断积累,该项研究得到逐步的深化。“八五”期间,水利界又对主流线作了深入分析,结果表明：各家所得结论不同,需要作进一步的分析讨论。我们认为：从长远的角度来看,小浪底水库清水下泄期间,黄河下游游荡性可段不对称的河谷形态不会改变;在继承性新构造运动造成的地壳向南掀沉、科氏力和人类活动的综合影响     

20世纪30年代珠江三角洲平原河网结构重建及最大槽蓄容量

基于1954年美国陆军制图局编制的中国地形图、1930―1934年日军参谋本部所绘中国地形图、广东省水文志和研究区各县县志等历史文图资料,重建研究区20世纪30年代的河网模型,对传统农业末期平原河网水系进行高精度复原,计算其最大槽蓄容量并分析其区域特点。结果表明：1）20世纪30年代珠三角河网（除干流河道）的最大槽蓄容量为6.78亿~20.75亿m³,其极值为20.75亿m³,平均值为13.38万m³/km²。其中1级河道最大槽蓄容量占总量的33.5%~49.1%,对于整个河网的容蓄洪水能力及水资源调度能力影响更大。与现阶段不同,传统农业时代末期（20世纪30年代）珠三角河网的槽蓄容量与河网密度呈正相关,槽蓄容量的大小受河网密度的影响较为明显。2）20世纪30年代珠三角河网的形成与传统时期的农业开发有着密切的关系,当时的河网水系是自然发育与该时期围田业对其开发、围垦的共同结果,围田开发的兴修堤围、挑挖河道等活动对于河网的扩展及其最大槽蓄容量的增加具有客观上的促进作用。     

塔里木河下游生态输水河道两侧区域地下水运动规律研究

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