A Method of Analysing Stream Channel Response to Environmental Change: Gauge data for the Tully River

Gauging data are available from numerous streams throughout Australia, and these data provide a basis for historical analysis of geomorphic change in stream channels in response to both natural phenomena and human activities. We present a simple method for analysis of these data, and a brief case study of an application to channel change in the Tully River, in the humid tropics of north Queensland. The analysis suggests that this channel has narrowed and deepened, rather than aggraded: channel aggradation was expected, given the intensification of land use in the catchment, upstream of the gauging station. Limitations of the method relate to the time periods over which stream gauging occurred; the spatial patterns of stream gauging sites; the quality and consistency of data collection; and the availability of concurrent land-use histories on which to base the interpretation of the channel changes.     

河西地区水、土资源的合理开发利用

通过调查计算,评述了河西地区水、土资源状况及开发利用过程中引起的环境变化和存在的主要问题,提出合理开发利用水、土资源的建议和意见:1.以流域为单元进行水、土资源合理利用布局,2.以水定地、搞好水土平衡,3.提高单位面积产量,适当扩大灌溉面积,4.合理利用和改良草场,5.种草种树,保护植被,6.提高水资源利用率。     

中国南方山地的土地荒漠化初探

我国的土地沙漠化已不仅仅在北方干旱、半干旱、包括部分半湿润地区, 而且在我国不少湿润和半湿润地带的东部平原(如黄淮海平原等)、沿海地区以及南方山地区也有发生, 其环境退化过程所包括的内容已不局限于"风沙化", 还包括了"砂石化"的类似砾质荒漠景观和山地丘陵斜坡的流水侵蚀造成的劣地景观, 内容较为丰富, 因此对我国南方山区的环境趋向于类似荒漠条件的退化过程, 我们采用了较广义的土地荒漠化的含义。     

天山南北麓新生代地理环境演变

本文阐明了晚第三纪以来天山的大幅度隆起及南北麓沉积过程,着重从古植被变化论述了区内新生代的环境演变,并对天山南北麓的沉积环境异同作了对比。文章中首次提出天山地区第三纪以来可分为两个湿润期(古新世-始新世,渐新世晚期-中新世)和三个干旱期(渐新世早中期、上新世、第四纪)。     

DCCA在黄土高原流域径流环境解释中的应用

以黄土高原腹地泾河流域12个水文特征指标为“物种”,选取对流域径流有影响的9个环境因子,采用DCCA排序方法定量分析河流径流特征沿环境因子梯度的演变规律。结果表明:(1)DCCA排序的前3轴分别与退化草地比率、降水量、降水强度、植被指数、平均坡度显著相关;(2)河流径流特征沿环境梯度可明显分为输沙量极大的北部黄土丘陵区;平均含沙量极高的中北部黄土沟壑区;径流量大、输沙量小的山地-沟壑过渡区;侵蚀模数极高、径流年内变化极大的中部黄土残塬区;产流量大、年含沙量极低的南部山地区。     

基于遥感数据的叶尔羌河流域水文过程模拟与分析

在西北荒漠-绿洲生态系统中,山区水循环对下游水资源管理具有重要作用。为了准确地理解高寒山区水文过程,以降水、温度和潜在蒸散发的遥感数据为模型输入,建立叶尔羌河流域的MIKE SHE模型。根据模型输出,从径流、积雪和蒸散发三方面探讨了流域的水文过程。结果表明：经校正后的遥感产品在叶尔羌河流域的水文模拟中取得了良好的应用效果,出山口卡群站日径流的效率系数达0.71,相关系数达0.85。河道的年平均径流深为146.66 mm,其中稳定的基流补给占21.3%。流域的年平均降雪231 mm,占总降水的74%左右;73.9%的融雪发生在7-9月,积雪主要分布于5000 m以上区域。蒸散发以7-9月中低山区植被覆盖良好的针叶林和草地为主。选用合适的方法对遥感数据进行验证和率定,有助于提高对资料缺失的高寒山区流域水文过程的认识。对不同水文要素进行分析验证,可更准确地理解水资源的转化、储存方式及其时空分布,以便为下游水资源管理提供依据。     

中国西南地区河流水文特性

对西南地区的山区、冰川—森林混合带和喀斯特等３种地貌类型的河流,从径流形成机理的角度对洪水过程与水量及其变化等特性作分析。     

Environmental changes in the central Po Plain (northern Italy) due to fluvial modifications and anthropogenic activities

The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area.This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating.In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations.Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the mountain sector of the basins and in-channel gravel extraction (now illegal but very intense in the 1960s and 1970s) are causing erosion along the rivers and along large sectors of the Adriatic coast. These changes are comparable with those occurring in basins of other Mediterranean rivers.     

浙江省山区综合开发的探讨

山区综合开发必须调整偏农型产业结构,实行合理利用自然资源和旨在使山区人口向山下流动的积极的社会经济政策,摆脱与分散性密切相关的自给自足观念。由于山区物质、信息流动阻力大,城镇发展宜取多核分散型,要注意交通等基础设施的超前建设,改善山区环境。     

Kadavu Island, Fiji: Fluvial Studies of a Volcanic Island in the Humid Tropical South Pacific

This paper examines features of drainage and stream channel form and process on the mountainous volcanic island of Kadavu in the humid tropical South Pacific, and interprets the findings in relation to island environmental characteristics such as geology, regolith soils, topography, vegetation and climate. At island and sub-island scales, drainage patterns are linked to the geographical arrangement and topography of the late Cenozoic volcanoes. Stream channel and bedload characteristics demonstrate the importance of both deep saprolite weathering profiles for supplying sediment into the fluvial system, and the high energy nature of the fluvial transport regimes. Landscape chemical denudation is estimated at 50-85 mm per 1,000 years from baseflow solute concentrations converted from water conductivity readings.
Relative tectonic and sea-level stability during the late Holocene and the largely undisturbed rainforest and savanna vegetation on the island suggest that climatic factors control rates of fluvial processes on Kadavu. Streamflow records show particularly that tropical storms can have a big impact. The effects of possible increasing numbers of cyclones in the South Pacific and human vegetation disturbance on Kadavu are considered.     

Downstream variation in bankfull width of wadeable streams across the conterminous United States

Bankfull channel width is a fundamental measure of stream size and a key parameter of interest for many applications in hydrology, fluvial geomorphology, and stream ecology. We developed downstream hydraulic geometry relationships for bankfull channel width w as a function of drainage area A, w = α A^β, (DHG_wA) for nine aggregate ecoregions comprising the conterminous United States using 1588 sites from the U.S. Environmental Protection Agency's National Wadeable Streams Assessment (WSA), including 1152 sites from a randomized probability survey sample. Sampled stream reaches ranged from 1 to 75 m in bankfull width and 1 to 10,000 km² in drainage area. The DHG_wA exponent β, which expresses the rate at which bankfull stream width scales with drainage area, fell into three distinct clusters ranging from 0.22 to 0.38. Width increases more rapidly with basin area in the humid Eastern Highlands (encompassing the Northern and Southern Appalachians and the Ozark Mountains) and the Upper Midwest (Great Lakes region) than for the West (both mountainous and xeric areas), the southeastern Coastal Plain, and the Northern Plains (the Dakotas and Montana). Stream width increases least rapidly with basin area in the Temperate Plains (cornbelt) and Southern Plains (Great Prairies) in the heartland. The coefficient of determination (r²) was least in the noncoastal plains (0.36–0.41) and greatest in the Appalachians and Upper Midwest (0.68–0.77). DHG_wA equations differed between streams with dominantly fine bed material (silt/sand) and those with dominantly coarse bed material (gravel/cobble/boulder) in six of the nine analysis regions. Where DHG_wA equations varied by sediment size, fine-bedded streams were consistently narrower than coarse-bedded streams. Within the Western Mountains ecoregion, where there were sufficient sites to develop DHG_wA relationships at a finer spatial scale, α and β ranged from 1.23 to 3.79 and 0.23 to 0.40, respectively, with r² > 0.50 for 10 of 13 subregions (range: 0.36 to 0.92). Enhanced DHG equations incorporating additional data for three landscape variables that can be derived from GIS—mean annual precipitation, elevation, and mean reach slope—significantly improved equation fit and predictive value in several regions, most notably the Western Mountains and the Temperate Plains. Channel width was also related to human disturbance. We examined the influence of human disturbance on channel width using several indices of local and basinwide disturbance. Contrary to our expectations, the data suggest that the dominant response of channel width to human disturbance in the United States is a reduction in bankfull width in streams with greater disturbance, particularly in the Western Mountains (where population density, road density, agricultural land use, and local riparian disturbance were all negatively related to channel width) and in the Appalachians and New England (where urban and agricultural land cover and riparian disturbance were all negatively associated with channel width).     

Bank Erosion in Fifteen Tributaries in the Glaciated Upper Susquehanna Basin of New York and Pennsylvania

The proportional contributions of cultivated lands and stream banks as sources of fine sediment loads were quantified in 15 rural watersheds in the Glaciated Appalachian Plateau region of the Susquehanna River basin of New York and Pennsylvania. We utilized a relatively simple method of fingerprinting sediment sources by comparing the concentrations of the nuclear bomb-derived radionuclide ¹³⁷ Cs in fluvial sediment samples collected from channel margins with sediment from cultivated fields and stream banks. The proportion of fine sediment from bank erosion ranged from none to 100% in the study tributaries, with a median contribution of 53% across the 15 study streams. In one stream with no evidence of bank sediment, anomalously high ¹³⁷ Cs levels in the samples indicated that the sources were pasture or forest, probably scoured from marshy floodplains upstream of the sampling sites. In the 14 other streams, cultivated lands accounted for an average of 42% of the fine sediment. We discuss sources of eroded bank material and the processes driving stream bank erosion in this glaciated region, and examine the impact of historic mill-dam deposits on bank erosion.     

A catchment-scale model of mountain stream channel morphologies in southeast Australia

The position of mountain streams high in the channel network and their proportional dominance mean that channel modifications and adjustments within these systems will have important implications for downstream processes and linkages. This study develops an analysis framework for examining the catchment-scale distribution of reach morphologies, and the relationship among reach type, catchment lithology and flow competence in southeast Australian mountain streams. The analysis framework is applied to three catchments which have contrasting proportions of the two dominant lithologies of the region, Devonian granites and Ordovician metasediments.The model successfully delineated 68% of reach types, and the resultant spatial maps allowed the effects of stream network position and catchment specific controls on channel morphology to be evaluated. Maximum lengths of the majority of reach morphology types were in second-order streams and the maximum number of morphology types (six) was present in third-order streams, with dramatic reductions in reach type variability as the network expands. The position of catchment lithology within the channel network structure was recognized as more important than the aerial extent of a particular lithology on the distribution and abundance of reach morphologies. The model provides an important tool in the management of channel networks for the protection or restoration of ecological diversity, by identifying river segments and tributaries with high morphological diversity.     

论山地气候带和气候型

本文论述了山地高度气候带与纬度气候带在形式上的联系和物理成因上的区别;在达种认识的基础上提出了划分山地高度气候带的基本原则,并提出山地最基本的气候型有四个,即高山气候,谷地气候,坡地气侯和高原气候。     

流域水系自动提取在西苕溪流域的应用

论述了如何基于栅格DEM自动提取流域自然水系的原理、方法和流程.以西苕溪中上游流域为例,根据DEM精度、上游集水区面积阈值和下垫面地形的不同,对所提取水系进行了比较.针对在平均地形坡度小于3°的平坦区域所提取水系与实际河网偏差较大的问题,提出了利用主干河道和平原水系数字化作为约束条件生成河网的新方法.     

Relationships between land-use and forced-pool characteristics in the Colorado Front Range

Land use practices in Colorado during the last two centuries altered the supply of sediment and water to many channels in the upper South Platte Basin. As a result of increased supply of sediment and mobility and reduced peak flows, the characteristics of pools associated with channel constrictions, referred to as forced pools, may have been altered. Increased supply of sediment and reduced transport capacity of high flows could lead to aggradation in forced pools. Channel confined by road corridors could lead to high velocities at normal flows, increased energy dissipation from riprap, or even increased pool frequency resulting from failed riprap. To assess potential alterations, four hypotheses were tested: (1) impacted streams will show significantly different mean volume of pools than a control stream; (2) mean volume of pools on streams where land-use activities increased the supply of sediment will be significantly different from streams solely affected by flow regulation; (3) the strongest change in characteristics of pools of impacted streams will be a reduced volume of pools; (4) streams affected by road corridors will show statistically lower spacing of pools than streams unaffected by roads. The downstream spacing and residual volume of twenty consecutive forced pools were surveyed on five streams in the Colorado Front Range that varied from no contemporary impact to multiple historical and contemporary impacts. ANCOVA with stepwise model selection indicated that degree of land-use (categorical), bankfull spacing of pools, upstream riffle slope and expansion ratio were all significant (α = 0.1) predictors of volume of pools (R² = 0.73). Simple linear regression of mean volume of pools and stream specific variables (gradient, drainage area and discharge) and least square means comparison of mean volume of pools indicated a need to standardize volumes of pools by slope and discharge so that the volumes of pools could be compared among different levels of land-use. Significant correlations between drainage area and volume of pools allowed volume of pools to be standardized by drainage area and thereby discharge. This dimensionless variable was also significantly correlated with channel slope, which permitted the construction of a new variable, PV_QS (volume of pools standardized by discharge and slope). Least square means comparison of mean PV_QS revealed that the control reach was significantly different from road-impacted reaches. Mean volume of pools was significantly larger in the control reach compared to all but one road-impacted stream. This was likely a function of higher wood loading in the control reach and the competence of high flows in the road-impacted reach. Streams affected by road corridors did not have significantly different bankfull spacing of pools from streams not impacted by roads. The multiple interactions among control and response variables explored in this study indicate the need to identify the most constrained and sensitive response variables when attempting to assess channel response to land use.     

Rates of stream incision in the middle part of the Arkansas River basin based on late Tertiary to mid-Pleistocene volcanic ash

Ages and elevations of ash layers correlated with late Tertiary and Pleistocene eruptions in the western US and present stream elevations are used to calculate net rates of incision by streams in the middle reaches of the Arkansas River basin in the south central US. The mean of the 23 measurements of rate of stream incision in the study area is 4.2±2.7 cm/ky with a range of 0.6 to 9.7 cm/ky. Major influences on rate of stream incision in the study area include the arid to semi-arid climate of the region, the type of material being incised by streams, stream captures, and salt dissolution in the bedrock that underlies the region. Rates of incision exceeded rates of basin filling but significant deposits of unconsolidated late Cenozoic sediments occur in the study area. Basins of streams that have incised the slowest since the late Tertiary contain the thickest and most extensive amounts of unconsolidated Quaternary sediments. Rates of incision by streams in the study area are similar to or slower than rates reported for streams elsewhere in the US and the world. Streams in mountainous regions and areas affected by rapid uplift have incised at rates orders of magnitude faster than streams in the study area.     

哈巴雪山自然保护区垂直气候带划分研究

依据哈巴雪山自然保护区及附近气候观测资料,应用气候学方法和原理,综合分析该自然保护区垂直气候要素,分析中发现,光照、气温、降水等气候要素,随海拔升高,垂直分异明显。依据气候特征的垂直变化,结合植被及土壤的分布,参照划分垂直气候带的标准,将保护区划分为7种气候带：河谷中亚热带、河谷北亚热带、山地暖温带、山地中温带、山地寒温带、高山寒带、高山永久冰雪带。分析结果表明：保护区垂直气候带特征分异明显,气候类型丰富多样;山地寒温带、高山寒带等地区,生态高度敏感脆弱。     

山区农业土地利用模式的设计

本文分析了市场经济条件下我国山区农业可持续发展所面临的问题 ,提出了山区农业土地利用模式的构想。指出影响我国山区农业土地利用模式的因素主要包括自然地理因素、市场因素和土地制度因素 ,特别是市场因素和土地制度因素对于农业土地利用模式设计的影响在新的历史时期尤为突出 ;强调山区农业土地利用模式设计必须遵循自然地带规律性、与农业经济多样化和规模经营相结合、与开拓产品市场相结合的原则 ;以河南省洛宁县为例具体说明了山区农业土地利用模式设计的技术路线。     

Spatiotemporal Dynamics of Landscapes of Plain and Mountain Catchments in the Altai Region During the Last 40 Years

The spatiotemporal dynamics of land covers of representative catchments of the Altai region (Altai Krai and Republic of Altai) was analyzed using remote sensing data and GIS techniques. The following key areas were used: the adjacent basins of Lake Gor’koe and the Kasmala and Barnaulka rivers on the Ob Plateau (Altai krai) were used for the inland drainage area of the Ob-Irtysh interfluve and the left bank of the Upper Ob; the Bol’shaya Rechka basin on the Biisk-Chumysh Upland and ancient Ob terraces (Altai krai), for the right bank of the Upper Ob; the Belaya river basin (Altai krai) for the low mountains and middle mountains of the Northwestern province of Russian Altai, and the Maima river basin (Republic of Altai) for the low mountains and middle mountains of the Northern and Northeastern Altai provinces. The algorithm for analyzing the actual state of land covers and identifying the main vectors of their transformation was adapted to the study area. A series of multitemporal Landsat images for three time slices was used. It is found that the plain catchments of the steppe and forest-steppe zones are characterized by a smaller amplitude of land cover change as compared to the mountain zones. For the inland drainage area of the Ob-Irtysh interfluve and the left bank of the Upper Ob, a reduction of the arable land and a high natural dynamics of water bodies are most indicative. The right bank of the Ob is characterized by the lowest dynamics of all types of land cover and a significant dynamics of artificial water bodies. In the mountain basins, a noticeable decrease in the forest areas largely in favor of natural grass communities was caused by the economic activities. It is also shown that the directions of changes and transitions of different types of land covers can differ greatly for different groups of landscapes.