Quantitative Modeling of Channelized Flow Within a Karst Stream

岩溶流内渠道化流的定量模拟

• 批准号: 0000725
• 负责人: Ellen Wohl
• 金额: $ 10.22万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0000725&HistoricalAwards=false
• 关键词: Quantitative; Modeling; Channelized; Flow; Within

0000725WohlPhysical and chemical erosion processes are rarely considered in tandem. Physical erosion processes have received rigorous, quantitative treatment in surface channels where on-going research has begun to integrate studies of reach-scale processes with landscape evolution and morphology. Chemical erosion processes have received considerable attention in karst terrains, but have yet to be fully integrated into studies of surface channels. Combining studies of physical and chemical erosion is desirable and is most needed in terrains where both may be of equal importance. The latter include fluviokarst where streamflow processes and landscape evolution are intimately linked to fluvial and karst processes. Using techniques initially developed for surface channels, open channel flow will be examined in an internally drained fluviokarst basin, Buckeye Creek, in southern West Virginia. Closed conduit flow will be examined using a quantitative model developed expressly for this project. Quantitative modeling of surface and subsurface flood flows will provide direct insight into the mechanisms by which fluviokarst streams erode while simultaneously transporting insoluble sediment derived from resistant strata in the headwaters of the basin. The latter processes must diverge from those in typical surface streams due to intermittent closed conduit flow in the cave(s) and backflooding upstream of cave entrances and passage constrictions. Although backflooding has the effect of increasing head and possibly flow velocities within constrictions, flow velocities and shear stress must decline upstream, with the result being a relative decrease in physical erosion and sediment transport above some threshold. The manner by which constrictions and their affected reaches are coupled is of direct relevance to mixed alluvial-bedrock streams. In both cases, the manner by which reaches with relatively high and low stream powers form continuous profiles despite dramatic differences in transport processes and capabilities is unknown and will be studied by quantifying flow properties in each type of stream segement. Simultaneously, the relative roles of chemical and physical erosion in shaping reach-scale and basin-scale stream morphologies and profiles will be addressed by numerical estimation of the ability of the surface and cave streams to abrade, pluck, and quarry, by direct measurement of sediment transport rates, and by directs measurement of solute transport in the cave stream.

物理和化学侵蚀过程很少被同时考虑。 物理侵蚀过程已收到严格的，定量的处理，在地面通道，正在进行的研究已经开始整合的研究达到规模的过程与景观演变和形态。 化学侵蚀过程在岩溶地区受到了相当大的关注，但尚未完全纳入地表通道的研究。 结合物理和化学侵蚀的研究是可取的，是最需要的地形，两者可能是同等重要的。 后者包括河流岩溶，其中径流过程和景观演变与河流和岩溶过程密切相关。 使用技术最初开发的表面渠道，明渠流量将在一个内部排水岩溶盆地，七叶树溪，在西弗吉尼亚州南部进行检查。 将使用专门为此项目开发的定量模型对封闭管道流进行检查。 地表和地下洪水流量的定量建模将提供直接洞察的机制，其中岩溶流侵蚀，同时运输来自盆地的源头的抵抗地层的不溶性沉积物。 后者的过程必须偏离那些在典型的表面流，由于间歇性封闭导管流在洞穴（S）和回流上游的洞穴入口和通道收缩。 虽然回洪具有增加水头和可能增加收缩区内流速的作用，但流速和剪切应力必须在上游下降，结果是物理侵蚀和泥沙输运在某一阈值以上相对减少。 收缩和受影响河段耦合的方式与混合冲积-基岩流直接相关。 在这两种情况下，达到相对较高和较低的流功率形成连续的配置文件，尽管在运输过程和能力的显着差异是未知的，将通过量化流特性在每种类型的流段进行研究。 同时，化学和物理侵蚀在塑造达到规模和流域规模的流形态和配置文件的相对作用将解决的表面和洞穴流磨损，采摘和采石场的能力的数值估计，通过直接测量泥沙输运率，并通过直接测量溶质运移在洞穴流。