NATURAL RESTABILIZATION OF STREAM CHANNELS IN URBAN WATERSHEDS1

ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5–35 km²) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross‐sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land‐use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still‐urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems.     

Numerical model of flow and pollutant transportation in non-orthogonal curvilinear coordinates

The planar 2D k-ε double equations‘ turbulence model was adopted and transformed into non-orthogonal curvilinear coordinates. The concentration convection-diffusion was introduced to planar 2D SIMPLEC algorithm of flow in non-orthogonal curvilinear coordinates. The numerical model of pollutant transportation in non-orthogonal curvilinear coordinates was constructed. The model was applied to simulate the flow and pollutant concentration fields. In the testing concentration field, two optimal operations of contamination discharging both along bank and in the centerline at the first bend of the meandering channel were adopted. Comparison with available data showed the model developed was successful, was valuable to engineering application.     

京津冀大气污染传输通道区大气污染时空格局研究

客观理解京津冀大气污染传输通道城市（“2+26”城市）空气污染时空格局对于区域大气污染联合防治具有重要意义.本研究采用遥感数据反演的PM_2.5浓度产品，利用趋势分析法和重心分析法，揭示了京津冀城市大气污染传输通道区2000~2015年大气污染时空格局演化特征.结果表明：（1）区域PM_2.5平均浓度整体呈现出太行山脉区域较低，太行山脉以东较高的格局，城镇地区明显高于周边地区.（2）2000~2015年区域PM_2.5年均浓度总体呈增加趋势，主要表现在2000~2007年，呈显著增加趋势的面积占全区的88.48%，之后呈稳定状态.（3）区域PM_2.5污染重心位于衡水、邢台和德州3市交界处，区域北部大气污染较严重.本研究可为京津冀及周边地区大气污染防治政策制定和措施实施提供参考与支持.     

基于正交试验方法的毛细矩形槽道平均流速影响因素分析

目的分析毛细矩形槽道平均流速的影响因素。方法通过公式推导毛细矩形槽道平均流速的有关影响因素,并且从中提取出部分因素,选用三因素三水平的正交试验表对流速进行分析,三因素分别为槽道宽度、槽道深度、槽道长度。通过CFX仿真得出对应的平均流速。结果得到了各因素水平变化对毛细矩形槽道平均流速的影响程度。槽道宽度及槽道深度对于毛细槽道平均流速具有比较大的影响,并得到最优的水平组合。结论对于毛细矩形槽道平均流速的影响因素给出了比较清晰的剖析,对于毛细矩形槽道传热的优化分析具有一定的参考意义。     

昆明城市生态河道建设探讨

在城市河道治理过程中，由于只片面强调防洪、排水，忽略了河道的其他功能，致使河道越挖越宽、越挖越深、越修越直，而河水越来越臭、越来越脏。建设生态河道是解决这些问题的唯一出路，既要顾及河道排洪、防洪等基本功能，又要保持河道生态系统的完整性。     

导流明沟人工湿地治理橡胶废水实践

运用人工湿地原理，采用明沟导流治理橡胶生产废水，其工程投资低，占地面积小，运行稳定，易于管理，去除率高，处理后废水达到国家标准。     

Improving the Urban Stream Restoration Effort: Identifying Critical Form and Processes Relationships

Stream restoration projects are often based on morphological form or stream type and, as a result, there needs to be a clear tie established between form and function of the stream. An examination of the literature identifies numerous relationships in naturally forming streams that link morphologic form and stream processes. Urban stream restoration designs often work around infrastructure and incorporate bank stabilization and grade control structures. Because of these imposed constraints and highly altered hydrologic and sediment discharge regimens, the design of urban channel projects is rather unclear. In this paper, we examine the state of the art in relationships between form and processes, the strengths and weaknesses of these existing relationships, and the current lack of understanding in applying these relationships in the urban environment. In particular, we identify relationships that are critical to urban stream restoration projects and provide recommendations for future research into how this information can be used to improve urban stream restoration design. It is also suggested that improving the success of urban restoration projects requires further investigation into incorporating process-based methodologies, which can potentially reduce ambiguity in the design and the necessity of using an abundant amount of in-stream structures.     

RIPARIAN FOREST EFFECT ON LATERAL STREAM CHANNEL MIGRATION IN THE GLACIAL TILL PLAINS1

ABSTRACT: Dendrochronology analyses of point bar complexes were used to quantify the effects of riparian forests on local lateral migration of bends in seven streams in the glacial till plains of north central Missouri. Stream bends were paired with similar bank height, midchannel radius of curvature, soil composition, and watershed size. In each pair, one concave bank was forested and one was unforested. Stream bends with unforested concave banks had an average local migration rate three times greater than stream bends that had forested concave banks.     

炼铁上料系统除尘设计体会点滴

就炼铁高炉矿槽除尘系统的方式，提出了一些革新的措施，涉及到阀门、吸气罩、风幕及控制方法等     

长江荆江分流河的河型及其洪灾防治探讨

从长江荆江分流河的河道平面形态及其近百年来的演变特征、河道比降、河道沉积特征、地质背景和地貌特征等方面进行了论述,认为这些河道是一个统一的网状河流体系。对各主要河道的输水输沙特征及其演变趋势和洪水灾害特征进行了讨论,结合网状河流系的基本特征,提出了洪灾防治的主要措施。