Quantitative Modeling of Channelized Flow Within a Karst Stream

物理侵蚀过程和化学侵蚀过程很少被同时考虑。物理侵蚀过程在地表水道中得到了严格的定量处理，正在进行的研究已经开始将河段尺度过程的研究与景观演变和地貌相结合。化学侵蚀过程在喀斯特地区受到了相当大的关注，但尚未完全纳入地表渠道的研究。物理侵蚀和化学侵蚀相结合的研究是可取的，在两者可能具有同等重要性的地形中是最需要的。后者包括河流岩溶，河流径流过程和地貌演变与河流沉积和岩溶过程密切相关。利用最初为地表渠道开发的技术，将在西弗吉尼亚州南部的七叶溪盆地内部排水的河流岩溶盆地中检查明渠水流。将使用专门为该项目开发的定量模型来检查封闭的管道流量。地表和地下洪水流动的定量模拟将直接揭示河流岩溶水流侵蚀的机制，同时输送来自盆地源头阻力层的不溶沉积物。后一种过程必然与典型地表河流的过程不同，因为洞穴内的间歇性闭合管道流动(S)以及洞口上游和通道狭窄的回灌。虽然回灌有增加水头和可能在狭窄内水流速度的效果，但上游水流速度和剪应力必须下降，其结果是超过一定阈值的物理侵蚀和泥沙输移相对减少。收缩和其受影响的河段的耦合方式与冲积-基岩混合河流直接相关。在这两种情况下，尽管输送过程和能力有很大差异，但具有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流分段中的流动特性来研究。同时，化学和物理侵蚀在形成河段尺度和盆地尺度河流形态和剖面中的相对作用，将通过对地表和洞穴河流磨损、采挖和采石能力的数值估计，通过直接测量泥沙输送速率，通过直接测量洞穴河流中的溶质输送来解决。

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.