Quantitative Modeling of Channelized Flow Within a Karst Stream

0000725 wohl物理和化学侵蚀过程很少同时考虑。物理侵蚀过程已经在地表河道中得到了严格的定量处理，在那里正在进行的研究已经开始将河段尺度过程与景观演化和形态的研究结合起来。化学侵蚀过程在喀斯特地形中受到了相当大的关注，但尚未完全纳入地表通道的研究。将物理和化学侵蚀的研究结合起来是可取的，并且在两者可能同等重要的地区是最需要的。后者包括河流岩溶，其中河流过程和景观演化与河流和喀斯特过程密切相关。利用最初为地表河道开发的技术，将在西弗吉尼亚州南部的一个内部排水的河流岩溶盆地Buckeye Creek中检查明渠水流。封闭管道流动将使用专门为本项目开发的定量模型进行检查。地表和地下洪水流量的定量建模将提供对河流岩溶流侵蚀的机制的直接洞察，同时运输来自盆地源头耐蚀地层的不溶性沉积物。后一种过程必须与典型地表水流的过程不同，这是由于洞内间歇性的封闭管道流动以及洞口上游的反淹和通道的收缩。虽然反驱具有提高收缩区水头和可能的流速的作用，但上游的流速和剪应力必须下降，其结果是物理侵蚀和输沙量在某个阈值以上相对减少。收缩带及其影响河段的耦合方式与混合冲积-基岩流直接相关。在这两种情况下，尽管在输送过程和能力上存在巨大差异，但相对较高和较低水流功率的河段形成连续剖面的方式是未知的，将通过量化每种类型河段的流动特性来研究。同时，化学和物理侵蚀在河段尺度和流域尺度溪流形态和剖面形成中的相对作用将通过对地表和洞穴溪流的磨蚀、采摘和采石能力的数值估计，通过对沉积物输送速率的直接测量，以及对洞穴溪流中溶质输送的直接测量来解决。

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.