Flow structure and channel change in a sinuous grass‐lined stream within an agricultural drainage ditch: Implications for ditch stability and aquatic habitat

Many drainage ditches in the Midwest have developed a geomorphological configuration characterized by vegetated bars, or benches, on the bottom of the ditch and a stream flowing within a channel inset into these bars or benches. Past work has focused on the sedimentology of the benches and the depositional processes involved in bench development. This study investigates the three‐dimensional flow structure and short‐term channel change in a small grass‐lined stream flanked by benches at the bottom of an agricultural drainage ditch in east central Illinois, USA. In particular, it focuses on the influence of channel curvature and bank vegetation on flow through the inset channel at two different stages and explores how the structure of the flow is related to documented patterns of channel change. Results indicate that the mean flow is characterized by a submerged high‐velocity core that mainly is confined to the centre of the channel by near‐bank zones of flow stagnation/separation induced by abrupt changes in channel alignment and by strong frictional effects of grasses extending into the flow along the channel margins. Where the high‐velocity core is close to the channel margins, minor erosional adjustments of the inset channel can occur in the form of bank erosion. Patterns of turbulence kinetic energy reflect the development of shear layers near the channel margins and surrounding the submerged high‐velocity core. Locations with strong turbulence also correspond to locations of minor bank erosion. The results indicate that the inset channel is a relatively stable feature, especially where the alignment of this channel is straight, but that erosion‐control treatments may be necessary locally where the inset channel impinges on the ditch bank. Although the development of benches, a geomorphic response to ditch maintenance, is commonly viewed as a threat to drainage efficacy, preserving or constructing benches and associated inset channels in drainage ditches can enhance aquatic habitat and water quality. Copyright © 2010 John Wiley & Sons, Ltd.     

化学灌浆在截污坝防渗帷幕中的应用

针对威海市垃圾处理厂截污坝帷幕渗透系数K≤5.52×10-7cm/s 的较高防渗要求,在截污坝帷幕灌浆工程中采用水泥灌浆结合HS酸性水玻璃材料对基础进行复合灌浆处理,采用这种工艺后的灌浆效果完全满足透水率＜0.044 Lu的设计要求。     

基于简易吸水法的喷灌施肥冬小麦冠层截留量

喷灌施肥时的冠层截留会增加叶片灼伤风险,影响肥料利用效率。为了定量评估喷灌施肥时冬小麦冠层的肥液截留特性,以尿素为研究对象,采用简易吸水法测定了冬小麦拔节-灌浆期不同尿素溶液浓度的冠层截留肥液量和附着肥液当量厚度。结果表明:冬小麦拔节-灌浆期冠层截留肥液量随冬小麦生长显著增加,冠层截留肥液量与植株生态指标显著线性相关,相关程度依次为株高>鲜重>植株表面积>叶面积指数;附着肥液当量厚度在拔节-灌浆期变化相对较小,变化范围为0.051～0.080 mm,均值为0.067 mm。在冬小麦抽穗期和拔节期,不同尿素溶液浓度的冠层截留肥液量和附着肥液当量厚度在p<0.05水平上差异显著。研究提出的冬小麦生育期内冠层截留肥液量与株高的回归方程可用以估算冬小麦生育期内喷灌施肥时的冠层截留肥液量。     

黄河下游堤防排水沟设计方法

根据黄河下游堤防堤顶区域的产汇流特性，将堤顶产汇流区概化为平行四边形区域，运用坡面水流运动波描述方法，计算了产汇流时间，提出了堤防排水沟设计洪峰流量计算公式、排水沟断面设计及间距的优化方法;并给出了实际例证。优化结果表明，黄河下游堤防排水沟间距为100m左右;排水沟断面为矩形时，宽取0.5m、深取0.4m；断面为梯形且边坡系数为2时，宽取0.4m、深取0.4m是比较合适的。     

渗渠产水量与滤管开孔率的关系研究

渗渠是一种传统的取水方式,广泛应用于生产和生活中。产水量是渗渠设计的重要指标。结合渗渠取水常用公式,在其他条件一定的情况下,就渗渠滤管开孔率对渗渠产水量的影响进行分析,得出相应的关系曲线图,拟合出渗渠产水量与滤管开孔率的经验公式。     

北京奥林匹克公园中心区雨水排放系统设计

由于规划用地内大面积设置雨洪利用设施,在雨洪利用设施设计标准范围内的雨水不允许排放,奥林匹克公园中心区雨水排放系统仅为超雨洪利用标准的道路广场以及休闲花园绿地内人行道等地面径流雨水的排放系统。因此,中心区雨水排放系统的雨量设计参数力求与雨洪利用设计标准配套,雨水收集系统的设计按照溢流排水的原则开发并采用了多项新型雨水的收集设施。中心区内景观道路与市政道路交织,包括多条机动车道,赛时,庆典广场等将会停放新闻采访等重型车辆。因此在管材、喾井的选型及管道开槽、基础、回填等方面采用了市政管线的做法,并采用了相关的市政施工规范及标准。     

渠系基础冻结过程水热耦合问题数值分析

本文对冬季条件下渠道基础冻结过程的非线性、非稳定水热耦合问题进行了数值模拟，应用系数效应滞后的变物性全隐差分格式对水热耦合问题进行了数值计算     

绵竹市清平乡塌洞沟泥石流发育特征及成因机制分析

清平乡塌洞沟受"5·12"地震影响,沟域内产生了大量松散物源,在暴雨等诱发条件下已爆发多次泥石流灾害。通过对该泥石流沟的详细调查,将沟域分为形成流通区及堆积区,并研究各区段冲淤特征及该泥石流的堆积特征,并对其成因机制进行分析。     

东辽河流域水土流失危害及治理措施

本文阐述梨树县东辽河流域水土流失的现状、危害及水土流失的成因和治理措施。     

平原漏斗区高效生态含水层补给技术研究

针对中国黄泛平原井灌地区地下水超采引起的大面积地下水漏斗问题,选择山东省临清市项目区,利用土壤水动力学、水力学和地下水动力学等相关理论,实施了地下水回灌工程对技术方案和参数进行设计,计算其回灌效果。通过计算结果可知,该回灌工程在7 d的引水过程中,增加了52 310.82 m~3的地下水补给量,占地下水补给总量的60.7%。野外回灌系统流速监测和示踪试验表明,该工程设计方案可行。在原沟渠渗入补给的基础上,该种明沟—暗管—竖井回灌补源工程增加了地下水补给量,对地下水漏斗恢复和旱涝碱综合治理具有重要作用。