Stream channel response to peak flows in a fifth-order mountain watershed
Stream channel response to peak flows in a fifth-order mountain watershed
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五级山地流域河道对洪峰流量的响应
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发表时间：
2000
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通讯作者：
J. M. Faustini
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作者：
J. M. Faustini
已批准：-' %L，'. tti（. !}朱莉娅艾伦J，pnes这项调查探讨了如何的幅度，风格和频率的通道调整随时间变化的空间内的第五阶山区流域。历史数据集，包括在二阶至五阶水道的五个地点进行长达20年的重复横截面调查和长达50年的流量记录，还得到了绘图和实地勘察活动的补充。这项研究有两个主要部分。第一个集中在两个相邻的，对比流达到检查大木质残体（LWD）的影响，通道形态和通道响应峰值流量在第三阶流。上游流经古老的森林与丰富的LWD，而下游是在1964-65年的皆伐，包含很少的LWD。1996年的一场25年一遇的洪水造成了LWD上游的沉积，并在老河段中交替出现了各步之间的冲刷，导致河段内的沉积物没有净增加或减少，而在皆伐河段中发生了广泛的冲刷和河床粗化。这些观察结果表明，到达尺度的信道响应的强烈影响，随钻测井丰度，但在更精细的尺度上的响应取决于随钻测井的位置和安排的细节。研究的第二部分研究了渠道响应的动态峰值流量超过二十年，并在此期间，在不同部分的渠道网络的两个特定的大洪水。断面数据表明，在研究地点的河床是非常稳定的，特别是在低阶通道。在90%的横截面上产生可检测变化的峰值流量-能够引起显著的河道调整的流量-在4”至5“h级Lookout Creek中的重现频率（每6-7年）大约是3级Mack Creek（20-25年）的3倍。据估计，在研究地点，平均每1.7至3.0年发生一次在25%横截面处产生可检测变化的流动。据估计，如果由于人为影响（例如，由于气候变化（如伐木）或气候变化，观测到的产生显著河道调整的洪峰流量频率在Lookout Creek将增加约30%，在Mack Creek将增加约60%。五级山区流域对洪峰流量的河道响应
Approved: -'% L,'. tti(. !} ` Julia Allen J,pnes This investigation explored how the magnitude, style, and frequency of channel adjustments vary spatially and over time within a 5th-order mountain watershed. Historical data sets, including repeated cross section surveys spanning up to 20 years at five sites on 2nd to 5th-order channels and streamflow records spanning up to 50 years, were supplemented by mapping and field reconnaissance activities. The study had two major parts. The first focused on two adjacent, contrasting stream reaches to examine the influence of large woody debris (LWD) on channel morphology and channel response to peak flows in a 3rd-order stream. The upper reach flows through old-growth forest with abundant LWD, while the lower reach was clearcut in 1964-65 and contains little LWD. A 25-year flood in 1996 caused deposition upstream of LWD steps in the old-growth reach alternating with scour between steps, resulting in no net gain or loss of sediment within the reach, while extensive scour and coarsening of the bed occurred in the clearcut reach. These observations suggest that reach-scale channel response was strongly influenced by LWD abundance, but that response at finer scales depends critically on the details of the location and arrangement of LWD. The second part of the study examined the dynamics of channel response to peak flows over two decades, and to two particular large floods during that period, in different portions of the channel network. The cross section data show that the streambed at the study sites is very stable, particularly in lower-order channels. Peak flows that produced detectable change at 90% of cross sections-flows able to cause significant channel adjustments-recur approximately three times as frequently (every 6-7 years) in 4`" to 5`h-order Lookout Creek as in 3rd-order Mack Creek (20-25 years). Flows that produced detectable change at 25% of cross sections are estimated to occur on average every 1.7 to 3.0 years at the study sites. It is estimated that if peak flows of all sizes were increased by only 10% due to anthropogenic impacts (e.g., logging) or climate change, the frequency of peak flows of a magnitude observed to produce significant channel adjustments would increase by approximately 30% in Lookout Creek and 60% in Mack Creek. Stream Channel Response to Peak Flows in a Fifth-Order Mountain Watershed