近30 年来深圳河网变化及其生态效应分析   总被引：12，自引：5，他引：7  

周洪建  史培军  王静爱  高路  郑憬  于德永 《地理学报》2008,63(9):969-980

在地形图、河道普查数据、遥感影像等多源数据支持下, 分析了深圳近30 年河网的时空变化规律及其与城市化水平的关系, 在此基础上通过分析植被盖度、生产有机物质的价值、生态系统服务价值、生态资产等指标的变化规律探讨了深圳观澜河流域河网变化的生态效应。 结果表明: (1) 近30 年深圳市河网结构趋于简单化、主干化, 河流支流发展受到较大限制; 河网总长度减少355.4 km, 总条数减少378 条, 河网密度从0.84 km/km² 降低到0.65 km/km²; 以区/ 街道办驻地为圆心, 半径为1-2 km 的圆环区成为河网萎缩、河网消失的主要 区域; 依据流域城市化水平和河流主干是否直接入海等2 个指标可将深圳市9 大流域/ 水系 分为4 种不同的河网变化类型; (2) 当城市化水平低于30%时, 城镇用地扩展与河网萎缩, 尤其是河网支流的萎缩存在显著相关; 当城市化水平大于30%时, 城镇用地扩展对河网的影响较小; (3) 2000-2005 年观澜河流域生态系统功能显著降低, 以生产有机物质价值降低幅度最 大(41%), 植被盖度次之(24%), 单位面积生态资产从2.79 元/m² 降低到2.34 元/m², 总生态 资产减少3136 万元; (4) 河网变化和城市化成为影响生态系统功能的主要因素, 其中河网变化因素和城市化因素对植被盖度降低的贡献率分别为23.1%和35.8%, 对生产有机物质价值减少的贡献率分别为25.1%和32.7%, 对生态系统服务价值减少的贡献率分别为7.7%和 56.2%, 对生态资产减少的贡献率分别为10.6%和52.2%。  相似文献   

新疆塔里木河流域水资源承载力评价研究   总被引：14，自引：3，他引：11  

孟丽红  陈亚宁  李卫红 《中国沙漠》2008,28(1):185-190

结合塔里木河2002年自然、社会和经济以及水资源资料,选取了耕地灌溉率、水资源利用率、供水模数、需水模数、人均供水量、生态用水率6个主要因素作为评价因素,应用模糊综合评判模型对塔里木河流域水资源承载能力进行了评价研究。结果表明,流域水资源开发利用已经达到相当规模,在现有经济技术条件下,该地区的水资源承载潜力已相对较小,水资源供需矛盾突出,应由耗水型经济结构向节水型经济结构转变,加强水资源的综合管理,以便科学、合理地利用流域内有限的水资源。  相似文献   

兰州银滩湿地区域生态经济价值评估   总被引：2，自引：2，他引：0  

王致萍  林栋 《中国沙漠》2008,28(2):322-325

通过分析人工湿地的生态系统服务功能,阐述了黄河湿地生物多样性保护与水文调控生态功能区的重要性,计算了兰州银滩湿地的固碳释氧、空气质量调节、水源涵养和科研文化四项核心生态经济价值。结果表明：银滩湿地核心生态经济价值理论值为1 623.7万元,其中固碳释氧和科研文化价值实现率较高,分别为324.88万元和11.53万元。但现状水分供给、生态结构方面尚存在不合理之处,通过合理配置树草种构成,优化引水渠道等措施,该湿地将发挥更大的生态经济效益。  相似文献   

The spatial and temporal patterns of aggradation in a temperate,upland, gravel‐bed river     

Emma K. Raven  Stuart N. Lane  Rob I. Ferguson  Louise J. Bracken 《地球表面变化过程与地形》2009,34(9):1181-1197

Intensive field monitoring of a reach of upland gravel‐bed river illustrates the temporal and spatial variability of in‐channel sedimentation. Over the six‐year monitoring period, the mean bed level in the channel has risen by 0·17 m with a maximum bed level rise of 0·5 m noted at one location over a five month winter period. These rapid levels of aggradation have a profound impact on the number and duration of overbank flows with flood frequency increasing on average 2·6 times and overbank flow time increasing by 12·8 hours. This work raises the profile of coarse sediment transfer in the design and operation of river management, specifically engineering schemes. It emphasizes the need for the implementation of strategic monitoring programmes before engineering work occurs to identify zones where aggradation is likely to be problematic. Exploration of the sediment supply and transfer system can explain patterns of channel sedimentation. The complex spatial, seasonal and annual variability in sediment supply and transfer raise uncertainties into the system's response to potential changes in climate and land‐use. Thus, there is a demand for schemes that monitor coarse sediment transfer and channel response. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Morphodynamics of a 1000‐year flood in the Kamp River,Austria, and impacts on floodplain morphology     

C. Hauer  H. Habersack 《地球表面变化过程与地形》2009,34(5):654-682

This paper investigates the impact of a 1000‐year flood in August 2002 on floodplains and valley morphology of an Austrian mixed alluvial bed rock river. Discharges with a recurrence interval between 500 and 2000 years caused distinctive overbank scouring and material deposition in the floodplains. After the 1000‐year flood, those morphologically affected areas were at random intervals documented over the whole longitudinal profile. In addition to overbank erosion in curved sections (cut‐offs), the river bed locally widened, floodplain stripping occurred and local overbank scours were documented along straight parts of the river. A hydrodynamic‐numerical model, combined with field measurements, was used to analyse the cause of these erosional landforms. Based on the modelled hydraulic conditions for a one‐year flood (30–78 m³ s^–1) and the catastrophic 2002 event (700–800 m³ s^–1), the numerical results allowed a cause‐effect study with 19 parameters. Deterministic and statistical analysis (ANOVA, discriminant analysis) showed that the morphodynamic effects of the 2002 flood were influenced by the variability of valley morphology of the Kamp River, which led partially to supercritical flow during flood constriction. These processes were in some cases also anthropogenically influenced. Lateral constriction and expansion of the valley geometry over short distances led to scouring and aggradation within the inundated areas during the event. These morphological features were therefore responsible for the elongated scour holes in the floodplains. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Implications of the saltation–abrasion bedrock incision model for steady‐state river longitudinal profile relief and concavity     

Leonard S. Sklar  William E. Dietrich 《地球表面变化过程与地形》2008,33(7):1129-1151

The saltation–abrasion model predicts rates of river incision into bedrock as an explicit function of sediment supply, grain size, boundary shear stress and rock strength. Here we use this experimentally calibrated model to explore the controls on river longitudinal profile concavity and relief for the simple but illustrative case of steady‐state topography. Over a wide range of rock uplift rates we find a characteristic downstream trend, in which upstream reaches are close to the threshold of sediment motion with large extents of bedrock exposure in the channel bed, while downstream reaches have higher excess shear stresses and lesser extents of bedrock exposure. Profile concavity is most sensitive to spatial gradients in runoff and the rate of downstream sediment fining. Concavity is also sensitive to the supply rate of coarse sediment, which varies with rock uplift rate and with the fraction of the total sediment load in the bedload size class. Variations in rock strength have little influence on profile concavity. Profile relief is most sensitive to grain size and amount of runoff. Rock uplift rate and rock strength influence relief most strongly for high rates of rock uplift. Analysis of potential covariation of grain size with rock uplift rate and rock strength suggests that the influence of these variables on profile form could occur in large part through their influence on grain size. Similarly, covariation between grain size and the fraction of sediment load in the bedload size class provides another indirect avenue for rock uplift and strength to influence profile form. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Fates of dissolved and particulate materials from the Mississippi river immediately after discharge into the northern Gulf of Mexico,USA, during a period of low wind stress     

M.J. Dagg  T. Bianchi  B. McKee  R. Powell 《Continental Shelf Research》2008

In June 2003, we conducted a two-part field exercise to examine biogeochemical characteristics of water in the lower Mississippi river during the 4 days prior to discharge and in the Mississippi river plume over 2 days after discharge. Here we describe the fates of materials immediately after their discharge through Southwest Pass of the Mississippi delta into the northern Gulf of Mexico. Changes in surface water properties immediately after discharge were much larger and more rapid than changes prior to discharge. Total suspended matter (TSM) declined, probably due to sinking, dissolved macronutrients were rapidly diminished by mixing and biological uptake, and phytoplankton populations increased dramatically, and then declined. This decline appeared to begin at salinities of approximately 10 and was nearly complete by 15. A large increase in dissolved organic carbon (DOC) occurred over approximately the same salinity range. Weak winds (<2 m s⁻¹) during and preceding this cruise apparently led to the formation of an extensive but thin freshwater lens from the river. This lens spread widely without much mixing, and the bloom of phytoplankton that occurred between discharge and a salinity of 10 was probably a freshwater community seeded from the lower river. Phytoplankton bloomed for a period of about 1–2 days, then declined dramatically, apparently releasing large amounts of DOC. Macronutrients from the river were utilized by the river phytoplankton community in the extensive freshwater lens. This contrasted with the more typical situation in which river nutrients stimulate a marine phytoplankton bloom at salinities in the mid-20s. We concluded that the direct effects of dissolved and particulate bio-reactive materials discharged by the Mississippi river were spatially restricted at this time to low-salinity water, at least as surface phenomena. After being transported through the lower river essentially unaltered, these materials were biogeochemically processed within days and tens of km. More generally, the mixing rate of plume water with receiving oceanic water has profound effects on the food web structure and biogeochemical cycling in the plume.  相似文献   

Wood as a driver of past landscape change along river corridors     

Robert A. Francis  Geoff E. Petts  Angela M. Gurnell 《地球表面变化过程与地形》2008,33(10):1622-1626

The role of wood as a driver of landform development appears to have been overlooked in the interpretation of palaeo‐landscape change along river corridors. Deforested river corridors and wood‐free rivers characterize ‘modern’, managed landscapes, but along natural river corridors both driftwood dynamics and tree reproductive strategies can have a dramatic impact on the style and rate of channel and floodplain development. Therefore, we believe that interpretations of the post‐glacial history of river valleys across the northern temperate climatic zone could be usefully reassessed, incorporating the roles of riparian trees. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Modeling fluvial response to in‐stream woody vegetation: implications for stream corridor restoration     

Sean J. Bennett  Weiming Wu  Carlos V. Alonso  Sam S. Y. Wang 《地球表面变化过程与地形》2008,33(6):890-909

River restoration and bank stabilization programs often use vegetation for improving stream corridor habitat, aesthetic and function. Yet no study has examined the use of managed vegetation plantings to transform a straight, degraded stream corridor into an ecologically functional meandering channel. Experimental data collected using a distorted Froude‐scaled flume analysis show that channel expansion and widening, thalweg meandering and riffle and pool development are possible using discrete plantings of rigid, emergent vegetation, and the magnitudes of these adjustments depend on the shape of the vegetation zone and the density of the vegetation. These experimental results were verified and validated using a recently developed numerical model, and model output was then used to discuss mechanistically how rivers respond to the introduction of in‐stream woody vegetation. Finally, a hybrid method of meander design is proposed herein where managed vegetation plantings are used to trigger or force the desired morphologic response, transforming a straight, degraded reach into a more functional meandering corridor. It is envisioned that such numerical models could become the primary tool for designing future stream restoration programs involving vegetation and assessing the long‐term stability of such activities. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Estimating suspended sediment concentrations from turbidity measurements and the calibration problem   总被引：1，自引：0，他引：1  

Jean P. G. Minella  Gustavo H. Merten  José M. Reichert  Robin T. Clarke 《水文研究》2008,22(12):1819-1830

In situ turbidity meters are being increasingly used to generate continuous records of suspended sediment concentration in rivers. However, the usefulness of the information obtained depends heavily on the existence of a close relationship between fluctuations in suspended sediment concentration and turbidity and the calibration procedure that relates suspended sediment concentration to the turbidity meter's signal. This study assesses the relationship between suspended sediment concentration and turbidity for a small (1·19 km²) rural catchment in southern Brazil and evaluates two calibration methods by comparing the estimates of suspended sediment concentration obtained from the calibrated turbidity readings with direct measurements obtained using a USDH 48 suspended sediment sampler. With the first calibration method, the calibration relationship is derived by relating the turbidity readings to simultaneous measurements of concentration obtained from suspended sediment samples collected from the vicinity of the turbidity probe during flood events. With the second method, the calibration is based on the readings obtained from the turbidity meter when the probe immersed in samples of known concentration prepared using soils collected from the catchment. Overall, there was a close link between fluctuations in suspended sediment concentration and turbidity in the stream at the outlet of the catchment, and the estimates of sediment concentration obtained using the first calibration method corresponded closely with the conventionally measured sediment concentrations. However, use of the second calibration method introduced appreciable errors. When the estimated sediment concentrations were compared with the measured values, the mean errors were ± 122 mg l^?1 and + 601 mg l^?1 for the first and second calibration procedures respectively. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献