Flow structure and channel change in a sinuous grass‐lined stream within an agricultural drainage ditch: Implications for ditch stability and aquatic habitat
Flow structure and channel change in a sinuous grass‐lined stream within an agricultural drainage ditch: Implications for ditch stability and aquatic habitat
复制标题
农业排水沟内蜿蜒草地溪流的水流结构和河道变化：对沟渠稳定性和水生栖息地的影响
DOI：
10.1002/rra.1430
复制
发表时间：
2012
影响因子：
2.2
通讯作者：
K. Massey
中科院分区：
文献类型：
--
作者：
B. Rhoads;K. Massey
中西部的许多排水沟渠已经形成了一种地貌结构，其特征是沟底有植被覆盖的条状或条状沟渠，沟渠中有一条溪流在这些条状或条状沟渠中流动。过去的研究主要集中在沉积学和沉积过程上。本研究调查了美国伊利诺斯州中东部一条农业排水沟底部一条两侧有长凳的草地小溪流的三维水流结构和短期河道变化。特别地，它侧重于河道曲率和河岸植被在两个不同阶段对流经嵌入河道的水流的影响，并探讨了水流结构与文献记载的河道变化模式之间的关系。结果表明，平均水流的特征是一个淹没的高速核心，它主要被限制在河道中心，这是由河道走向突变和沿河道边缘延伸到水流中的草的强烈摩擦作用引起的近岸流动停滞/分离区。当高速岩心靠近河道边缘时，嵌入的河道会以河岸侵蚀的形式发生轻微的侵蚀调整。湍流动能模式反映了通道边缘附近和淹没高速岩心周围剪切层的发育。湍流较强的地区也与河岸侵蚀较小的地区相对应。结果表明，嵌入沟道是一个相对稳定的特征，特别是在该沟道的走向是笔直的地方，但在嵌入沟道与沟岸碰撞的地方，可能需要进行侵蚀控制处理。虽然滩滩的发展是对沟渠维修的一种地貌反应，通常被视为对排水效能的威胁，但在排水沟渠中保留或建造滩滩和相关的嵌入渠道可以改善水生生境和水质。版权所有©2010 John Wiley & Sons， Ltd
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.