城市河流整治的生态规划要点——以北京市温榆河为例

在城市化进程中人们对城市河流的利用强度日益增大,在饱受污染危害之后,城市的规划和建设者注意到,河流不仅是饮水之源、排污渠道,更是人类生存的重要生态依托,因此,碧水工程已经成为各地城市生态整治的工作重点。但是,河流的生态功能是什么？服务功能又是什么？碧水工程不应只解决水质污染问题,而应保护和恢复河流的生态功能,利用好河流的生态服务功能。本文以北京市温榆河的生态规划为例,充分尊重河流的线性廊道特征,在景观生态学理论和技术的支持下,提出了修复温榆河生态通道功能和恢复天然河流水的运动规律的生态建设要点。     

我国公路交通防抗极端天气灾害的应急探讨

极端天气事件将变得更加频繁和剧烈,为了提高我国公路交通防抗极端天气灾害的应急能力,采用分析对比和调查研究的方法,探讨我国公路交通在防抗2008年南方大雪灾中的应急管理工作与处置技术,研究国内外目前应对极端天气的成功经验。结果表明:我国公路交通防抗极端天气灾害主要在组织机构、责任机制、信息渠道和处置技术等方面存在问题。通过提出我国公路交通防抗极端天气应急处置的具体流程,可以迅速控制、减轻和消除公路交通极端天气引起的危害,及时恢复公路交通正常通行。     

Initial Adjustments Within a New River Channel: Interactions Between Fluvial Processes, Colonizing Vegetation, and Bank Profile Development

A conceptual model of the morphological development of the riparian margins of newly cut river channels is presented, suggesting early feedbacks between vegetation growth and bank form. To test the model, observations of long and cross profiles, bank sediment and seed deposition, and bank vegetation development were collected over the first 2 years of river flows through a reach of the River Cole, West Midlands, UK. The newly created channel had a sinuous planform and varying asymmetric trapezoidal cross section in sympathy with the planform. No imposed bedforms or bank reseeding were included in the design. Over the 2 years, development of bedforms was rapid, with bed sediment sorting and bank profile adjustment occurring more steadily and progressively. Six classes of bank profile were identified by the end of the study period, illustrating close associations with sediment aggradation, vegetation colonization, and growth patterns. Vegetation colonization of the banks was seeded predominantly from local sources during the summer and from hydrochory (transport by the river) during the winter. Colonizing vegetation on the riverbanks appeared to act as a significant propagule source by the second summer and as an increasingly important roughness element, trapping both propagules and sediment, within the second year and providing early feedback into bank evolution. As a result, the time required for riparian margin development in the conceptual model was found to be considerably longer than observed in the study river. In addition, the role of surface wash/bank failure in modifying the bank profile and transporting seeds onto the upper bank face during the first year of bank development was found to be important in initiating rapid bank vegetation colonization and surface stabilization. This set of processes had not been incorporated in the initial conceptual model. In relation to channel restoration, this research illustrates that in small temperate rivers of modest energy the provision of an initial, sinuous corridor is sufficient to induce rapid development of fluvial features and vegetation cover without the need to construct bed forms or to seed the banks.     

CHANNEL STABILITY DOWNSTREAM FROM A DAM ASSESSED USING AERIAL PHOTOGRAPHS AND STREAM‐GAGE INFORMATION1

ABSTRACT: The stability of the Neosho River channel downstream from John Redmond Dam, in southeast Kansas, was investigated using multiple‐date aerial photographs and stream‐gage information. Bankfull channel width was used as the primary indicator variable to assess pre‐ and post‐dam channel change. Five sin‐mile river reaches and four stream gages were used in the analysis. Results indicated that, aside from some localized channel widening, the overall channel change has been minor with little post‐dam change in bankfull channel width. The lack of a pronounced post‐dam channel change may be attributed to a substantial reduction in the magnitude of the post‐dam annual peak discharges in combination with the resistance to erosion of the bed and bank materials. Also, the channel may have been overwidened by a series of large floods that predated construction of the dam, including one with an estimated 500‐year recurrence interval.     

长距离人工输水渠道水质时空演变规律研究——以南水北调中线总干渠为例

以南水北调中线工程通水6年来沿线30个常规水质监测断面逐月的水质监测数据为基础,基于斯皮尔曼秩次相关检验,系统分析总干渠水质时空变化趋势.结果表明,总干渠水质总体良好,主要指标能够达到Ⅱ类及以上水平.空间尺度上,总干渠水温(r=-0.897,p＜0.01)、总磷(r=-0.820,p＜0.01)、生化需氧量(r=-0....     

TIMBER HARVEST IMPACTS ON SMALL HEADWATER STREAM CHANNELS IN THE COAST RANGES OF WASHINGTON1

ABSTRACT: We evaluated changes in channel habitat distributions, particle‐size distributions of bed material, and stream temperatures in a total of 15 first‐or second‐order streams within and nearby four planned commercial timber harvest units prior to and following timber harvest. Four of the 15 stream basins were not harvested, and these streams served as references. Three streams were cut with unthinned riparian buffers; one was cut with a partial buffer; one was cut with a buffer of non‐merchantable trees; and the remaining six basins were clearcut to the channel edge. In the clearcut streams, logging debris covered or buried 98 percent of the channel length to an average depth of 0.94 meters. The slash trapped fine sediment in the channel by inhibiting fluvial transport, and the average percentage of fines increased from 12 percent to 44 percent. The trees along buffered streams served as a fence to keep out logging debris during the first summer following timber harvest. Particle size distributions and habitat distributions in the buffered and reference streams were largely unchanged from the pre‐harvest to post‐harvest surveys. The debris that buried the clearcut streams effectively shaded most of these streams and protected them from temperature increases. These surveys have documented immediate channel changes due to timber harvest, but channel conditions will evolve over time as the slash decays and becomes redistributed and as new vegetation develops on the channel margins.     

CHANGING NEAR‐STREAM LAND USE AND RWER CHANNEL MORPHOLOGY IN THE VENEZUELAN ANDES1

ABSTRACT: The shape of a river channel is linked to surrounding land use through interacting hydrologic and geologic processes. This study analyzes the relationship between the change in near‐stream land use and the shape of the adjacent river channel over time. Three watersheds in the foothills of the Venezuelan Andes that have experienced differing degrees of development were studied to determine river channel width, sinuosity, and position relative to surrounding land use. Change in land use over time was obtained from multiple‐date aerial photographs (1946 and 1980) referenced to 1996 Landsat Thematic Mapper (TM) satellite imagery, and verified by field inspection. Measurements of land‐use type and amount and river channel morphology from the two dates were made using geographic information system (GIS) methods. The three watersheds differed in the extent of deforestation, the location of remaining forested land, and how much land‐use change had already occurred by 1946. Change in river channel morphology was greatest at the most deforested sites. Valley shape and channel constraint also had a discernible effect on change in channel morphology. This study introduces a method for analyzing change in coupled terrestrial‐aquatic systems based on multiple‐date, remotely sensed data and GIS analysis of spatial properties. The results document human impacts on river channels through a comparison of multiple watersheds over a 35‐year time interval.     

界牌河段航道整治工程对白Ji豚和长江江豚影响评价研究

界牌河段航道整治工程于１９９４年动工,１９９８年基本结束。为了防止在施工过程中对白Ｊｉ豚和长江江豚造成意外伤害,并对整治河估的环境变化对白Ｊi豚和长江江豚的影响 作出了评价,作者在１９９５年至１９９９年在界牌河段对白Ｊi豚和江豚的活动和航道整治前后的情况进行了监测。调查结果表明,介牌般道在整 治过程中没有对白Ji豚和江豚造成伤害,原来百航严重的界牌航道得到了有效的整治,同时也有利于白Ｊi豚和江豚的活动     

Channel adjustments to the removal of log steps: an experiment in a mountain stream

Fallen trees and their large debris often form log steps in small mountain streams, where they are incorporated into the hydraulic geometry. The hypothesis here was that these log steps take the place of gravel bars that otherwise would have been required for channel slope adjustment. In this experiment, the treated as well as the control stream were located in virgin mixed conifer forests and until the study began, no human activity had interfered with the natural developments. All log steps were removed from a stream and the formation of new log steps was prohibited by periodic removal of fallen trees and branches. Five years later, 74% of all removed log steps had been replaced by gravel bars, thus proving the hypothesis that increased bedload movement was required to offset the loss of log steps. Implications are that streamside forests should be managed so that they can provide a steady supply of debris for channel stability.     

南水北调中线总干渠水体耗氧特征及成因

为揭示南水北调总干渠水体耗氧物质的种类及其潜在来源,对总干渠沿线进行了水样采集,并分析了总干渠水体的耗氧因子的分布及其耗氧成因.结果表明,从渠首到北盘石监测断面,高锰酸盐指数低于国家地表水Ⅰ类水质标准值（2 mg·L^-1）,北盘石以北（除惠南庄断面）几乎全部高于2 mg·L^-1.溶解性有机质（DOM）、NH₃-N和NO₂^--N浓度在总干渠沿程呈波动特征;Fe²⁺和Mn²⁺浓度在北盘石以南断面较为稳定,之后分别呈降低和升高趋势.基于上述物质耗氧的化学计量关系,DOM耗氧量均值为1.86 mg·L^-1,对高锰酸盐指数的平均贡献率超过了70%;无机物质中NH₃-N耗氧量最高,平均为0.134 mg·L^-1,而NO₂^--N、Fe²⁺及Mn²⁺的耗氧量均低于0.1 mg·L^-1.对主要耗氧因子DOM的三维荧光分析结果表明,荧光指数（FI）、自生源指数（BIX）、腐殖化指数（HIX）变化范围分别为1.68~3.62、0.68~1.22、1.47~3.04,表现出较强的自生源特征,DOM内源输入占比达到了71.63%~80.94%,并且在藻类爆发期,藻密度突变点与高锰酸盐指数的突变点高度吻合.上述结果表明主要来源于自身藻类和微生物的DOM是导致总干渠沿程高锰酸盐指数升高的主要原因,干渠自身生物化学过程对水质的影响值得长期关注.