Mitigating the Effects of Landscape Development on Streams in Urbanizing Watersheds

This collaborative study examined urbanization and impacts on area streams while using the best available sediment and erosion control (S&EC) practices in developing watersheds in Maryland, United States. During conversion of the agricultural and forested watersheds to urban land use, land surface topography was graded and vegetation was removed creating a high potential for sediment generation and release during storm events. The currently best available S&EC facilities were used during the development process to mitigate storm runoff water quality, quantity, and timing before entering area streams. Detailed Geographic Information System (GIS) maps were created to visualize changing land use and S&EC practices, five temporal collections of LiDAR (light detection and ranging) imagery were used to map the changing landscape topography, and streamflow, physical geomorphology, and habitat data were used to assess the ability of the S&EC facilities to protect receiving streams during development. Despite the use of the best available S&EC facilities, receiving streams experienced altered flow, geomorphology, and decreased biotic community health. These impacts on small streams during watershed development affect sediment and nutrient loads to larger downstream aquatic ecosystems such as the Chesapeake Bay.     

Sediment–Water Interactions in an Eroded and Heavy Metal Contaminated Peatland Catchment,Southern Pennines,UK

Atmospherically deposited lead in the upper layer of the heavily eroded peatlands of the Peak District, southern Pennines, UK, reaches concentrations in excess of 1,000 mg kg⁻¹. Erosion of the upper peat layer in this region is releasing lead, associated with eroded peat particles, into the fluvial system. Understanding the process mechanisms that control dissolved lead concentrations in contaminated peatland streams is vital for understanding lead cycling and transport in peatland streams. Many headwater streams of the southern Pennines recharge drinking water reservoirs. Measurements in the Upper North Grain (UNG) study catchment show that mean sediment-associated and dissolved lead concentrations are 102 ± 39.4 mg kg⁻¹ and 5.73 ± 2.16 μg l⁻¹, respectively. Experimental evidence demonstrates that lead can desorb from suspended sediments, composed of contaminated peat, into stream waters. In-stream processing could therefore account for the elevated dissolved lead concentrations in the fluvial system of UNG.     

1999年6月16日大咕噜沟泥石流

通过对岷江大咕噜沟 1999 0 6 16泥石流的数次现场考察与观测 ,首先叙述了本次泥石流的活动及其危害情况 ,描述了泥石流的形成条件 ,指出了泥石流发生的原因 ,认为本次泥石流是由于大咕噜沟流域内物质的含水量较高 ,在连续暴雨的条件下其含水量将会超饱和 ,引起二岔沟以上南支右岸海拔 3750m处的沟岸滑 ,进而产生泥石流的。然后对流沟沟床演变以及单侧支流入汇的影响进行了分析 ,认为大咕噜沟主沟呈串珠状沟道 ,平面上宽窄相间 ,纵剖面为深潭—跌水形式 ,跌坎的形成通常有以下三种情况 :一种是沟床本身为岩石或含有岩石 ,一种是两岸崩塌或滑坡而残留的粗大堆积物形成 ,一种是支流的冲出物或堆积扇形成。另外 ,同岸支沟的存在使主河逼近对岸 ,在岩坡稳定性较差的条件下 ,使对岸产生相当规模的崩塌或滑坡。最后 ,提出防治泥石流灾害的建议。     

三峡库区王家桥小流域土壤侵蚀因子初步研究

通过对王家桥小流域土壤，降雨，植被和地形等因子的分析，探讨了土壤抗侵蚀性能，分析了坡面侵蚀与各影响因子间的关系，建立了基于降雨基础上的全流域输沙幂函数回归方程。结果表明，本地区土壤因具有较强的渗透性，抗冲，抗蚀和抗剪切破坏的能力，而使其保持较小的可侵蚀性；坡面侵蚀中的主要影响因素是雨强和径流量（或降雨量）的大小；流域内土壤侵蚀的形式主要表现为暴雨作用下的重力侵蚀，在影响土壤侵蚀的诸多因子中降雨是关键性的，它的强度和年分布对年侵蚀模数的大小具有决定性作用。同时，通过分析各种雨强（平均雨强，最大雨强，最大15分钟雨强，最大30分钟雨强，最大60分钟雨强）对土壤侵蚀量的影响，结果表明，虽然最大60分钟雨强具有最优相关性，但在多元回归方程中，采用最大30分钟雨强回归效果最佳。     

云南松林控制坡地侵蚀的机械效应分析

坡面稳定性的机械效应包括土壤加强作用、斜向支撑作用、坡面负荷作用、风力传递和根楔壁作用。试验证明 ,云南松林通过其机械效应加强了林区土壤稳定性 ,提高了土层的抗剪强度。云南松林的机械效应及其作用在土壤侵蚀控制和斜坡保护、滑坡泥石流防治、坡面生态工程应用等方面具有广阔的应用前景。在云南省实践应用中具有较好的可行性     

三江源植被保持土壤能力的时空变化

为深入了解三江源区植被保持土壤的能力,以RS和GIS为技术支撑,在对三江源区植被覆盖度动态变化特征分析的基础上,利用SL190—2007《土壤侵蚀分类分级标准》推荐的中国土壤侵蚀模型CSLE(Chinese soil loss equation)估算了2000—2010年三江源区植被的土壤保持能力,并分析其时空动态变化特征. 结果表明:①2000—2010年三江源区年均植被覆盖度为43%~50%;植被平均土壤保持量为849~955 t/km2,并且空间差异很大,总体上呈自西北向东南增加的空间分布格局. ②2000—2010年植被的土壤保持能力呈逐渐增加趋势,其中2000—2005年各流域的土壤保持能力平均增加了约29 t/km2,并以大夏河与洮河流域土壤保持能力的增幅(约700 t/km2)最大,其次为玛曲至龙羊峡(约300 t/km2),羌塘高原区植被的土壤保持能力增幅(仅2.08 t/km2)最小;2005—2010年各流域的土壤保持能力呈现轻微增长,平均增加了约9 t/km2,其中增幅较大的是柴达木盆地东和直门达至石鼓流域(约16 t/km2),增幅最小的是羌塘高原区(仅3.90 t/km2). ③三江源植被土壤保持能力随植被覆盖度的增加呈非线性增长,可通过指数或幂函数形式表达. 研究显示,增加植被覆盖度有助于提高三江源区的土壤保持能力、控制区域土壤侵蚀.      

液态危险品智能储运装置的设计

危险品的储存和运输关系到人们的生命和财产安全,设计开发一套能够保障危险品安全的智能储运装置以及泄漏预警系统具有重要意义。分析液态危险品泄漏监测研究现状,设计一套以双层储运桶和远程智能预警器为主要硬件的智能储运装置,以及配套的危险品泄漏监测、预警系统。装置和系统通过气压传感器采集泄漏信息,GPS模块定位位置信息,感应标签读取物流信息,借助SIM模块发送给监管中心和驾驶员,达到监测和预警的目的。储运装置具有防撞防漏、自动测漏等功能,能够对液态危险品进行实时监测和及时预警。     

页岩气压裂弯管中液固两相流冲蚀磨损的数值模拟

为了研究超高压水力压裂下支撑剂颗粒进入弯管后冲蚀磨损区域的变化特性。基于液-固两相流理论、Fluent冲蚀模型建立弯管冲蚀模型,结合弯管内流场分析颗粒运动轨迹,引入斯托克斯数（St）探究冲蚀磨损区域变化,并进行数值分析。研究结果表明:弯管中冲蚀磨损发生区域有5处,主要严重区域有3处,弯管流场会改变固体颗粒数量及对壁面冲击动能与运动轨迹,St变化会明显引起冲蚀磨损区域的规律性变化;随着St从0~1至St>1变化,弯管段内壁面外侧（液体进入弯管后的正对区域）与直管段靠近弯管段的侧方区域的冲蚀磨损情况呈现“此消彼长”的规律性差异;管径越小,最大冲蚀速率的增长幅度越明显,增大管径,是减小冲蚀磨损的有效途径。研究结果对压裂弯管的改进设计及管道安全防护具有指导作用。     

Streamflow,Sediment Transport,and Geomorphic Change during the 2011 Flood on the Missouri River Near Bismarck–Mandan,ND

Geomorphic change from extreme events in large managed rivers has implications for river management. A steady‐state, quasi‐three‐dimensional hydrodynamic model was applied to a 29‐km reach of the Missouri River using 2011 flood data. Model results for an extreme flow (500‐year recurrence interval [RI]) and an elevated managed flow (75‐year RI) were used to assess sediment mobility through examination of the spatial distribution of boundary or bed shear stress (τ_b) and longitudinal patterns of average τ_b, velocity, and kurtosis of τ_b. Kurtosis of τ_b was used as an indicator of planform channel complexity and can be applied to other river systems. From differences in longitudinal patterns of sediment mobility for the two flows we can infer: (1) under extreme flow, the channel behaves as a single‐thread channel controlled primarily by flow, which enhances the meander pattern; (2) under elevated managed flows, the channel behaves as multithread channel controlled by the interaction of flow with bed and channel topography, resulting in a more complex channel; and (3) for both flows, the model reach lacks a consistent pattern of deposition or erosion, which indicates migration of areas of erosion and deposition within the reach. Despite caveats and limitations, the analysis provides useful information about geomorphic change under extreme flow and potential implications for river management. Although a 500‐year RI is rare, extreme hydrologic events such as this are predicted to increase in frequency.     

西藏公路建设工程土壤侵蚀预测研究

西藏地区公路建设过程中的水土保持一直以来是必须面对的机遇与挑战。文章以国道318线通麦段公路改建项目为例,对工程施工造成的土壤侵蚀类型和强度进行了预测分析。根据实地调查,项目区可划分为主线防治区、病害整治防治区、施工场地、取料场、弃渣场5个区域,文章分别对其扰动地表而可能产生的水土流失量进行了预测。结果显示预测期内工程水土流失总量约10 990 t,其中弃渣场、路基边坡流失量较大,应属于水土流失的重点防治区。