...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Geomorphology >Lithologic and hydrologic controls of mixed alluvial-bedrock channels in flood-prone fluvial systems: Bankfull and macrochannels in the Llano River watershed, central Texas, USA
【24h】

Lithologic and hydrologic controls of mixed alluvial-bedrock channels in flood-prone fluvial systems: Bankfull and macrochannels in the Llano River watershed, central Texas, USA

机译：易发生洪灾的河流系统中混合冲积基岩渠道的岩性和水文控制：美国德克萨斯州中部拉诺河流域的河岸河道和大型河道

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The rural and unregulated Llano River watershed located in central Texas, USA, has a highly variable flow regime and a wide range of instantaneous peak flows. Abrupt transitions in surface lithology exist along the main-stem channel course. Both of these characteristics afford an opportunity to examine hydrologic, lithologic and sedimentary controls on downstream changes in channel morphology. Field surveys of channel topography and boundary composition are coupled with sediment analyses, hydraulic computations, flood-frequency analyses, and geographic information system mapping to discern controls on channel geometry (profile, pattern, and shape) and dimensions along the mixed alluvial-bedrock Llano River and key tributaries. Four categories of channel classification in a downstream direction include: (ⅰ) uppermost ephemeral reaches, (ⅱ) straight or sinuous gravel-bed channels in Cretaceous carbonate sedimentary zones, (ⅲ) straight or sinuous gravel-bed or bedrock channels in Paleozoic sedimentary zones, and (ⅳ) straight, braided, or multithread mixed alluvial-bedrock channels with sandy beds in Precambrian igneous and metamorphic zones. Principal findings include: (ⅰ) a nearly linear channel profile attributed to resistant bedrock incision checkpoints; (ⅱ) statistically significant correlations of both alluvial sinuosity and valley confinement to relatively high f (mean depth) hydraulic geometry values; (ⅲ) relatively high b (width) hydraulic geometry values in partly confined settings with sinuous channels upstream from a prominent incision checkpoint; (ⅳ) different functional flow categories including frequently occurring events (＜ 1.5-year return periods) that mobilize channel-bed material and less frequent events that determine bankfull channel (1.5- to 3-year return periods) and macrochannel (10- to 40-year return periods) dimensions; (ⅴ) macrochannels with high f values (mostly ≥0.45) that develop at sites with unit stream power values in excess of 200 watts per square meter (W/m~2); and (ⅵ) downstream convergence of hydraulic geometry exponents for bankfull and macrochannels, explained by co-increases of flood magnitude and noncohesive sandy sediments that collectively minimize development of alluvial bankfull indicators. Collectively, these findings indicate that mixed alluvial-bedrock channels exhibit first-order lithologic controls (lithologic resistance and valley confinement) of channel geometry, second-order hydrologic (flow regime) control of channel dimensions, and third-order sedimentary controls that exert subsidiary influence on channel shape and bed configuration.
机译：位于美国得克萨斯州中部的乡村且不受管制的拉诺河流域，水流状况变化很大，瞬时峰值流量范围很广。沿主干通道过程存在表面岩性的突然转变。这两个特征为检查水道形态下游变化的水文，岩性和沉积控制提供了机会。渠道地形和边界成分的现场调查与沉积物分析，水力计算，洪水频率分析以及地理信息系统映射相结合，以识别沿混合冲积基岩拉诺河道的几何形状（剖面，样式和形状）和尺寸的控制河流和主要支流。下游方向的河道分类分为四类：（ⅰ）最短暂的河床段；（ⅱ）白垩纪碳酸盐岩沉积区的平直或弯曲砾石床通道；（ⅲ）古生代沉积区的平直或弯曲砾石床或基岩通道。 ，以及（ⅳ）前寒武纪火成岩和变质带中带沙质床的直，辫状或多螺纹混合冲积基岩通道。主要研究结果包括：（ⅰ）归因于抗性基岩切口检查点的近乎线性通道剖面； （ⅱ）冲刷弯曲度和谷底限制与相对较高的f（平均深度）水力几何值的统计显着相关性； （ⅲ）在部分密闭的环境中具有较高的b（宽度）水力几何值，且在明显的切口检查点上游有弯曲的通道； （ⅳ）不同的功能流类别，包括动员渠道床物质的频繁发生的事件（＜1.5年的回报期）和确定银行满渠道（1.5至3年的回报期）和宏观渠道（10至40的较不频繁的事件）年回报期）维度； （ⅴ）在单位流功率值超过每平方米200瓦（W / m〜2）的地点发展的，具有高f值（通常≥0.45）的宏信道； （ⅵ）堤岸和大河道的水力几何指数的下游收敛性，可以通过洪水幅度和非粘性砂质沉积物的共同增加来解释，这共同使冲积堤岸指标的发展最小化。总体而言，这些发现表明，混合冲积基岩通道表现出通道几何形状的一阶岩性控制（岩性和谷底限制），通道尺寸的二阶水文（流动状态）控制以及发挥辅助作用的三阶沉积控制。对通道形状和床配置的影响。

著录项

相似文献

  • 外文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号