Channel bed adjustments following major aggradation in a steep headwater setting: findings from Oyabu Creek, Kyushu, Japan
Channel bed adjustments following major aggradation in a steep headwater setting: findings from Oyabu Creek, Kyushu, Japan
复制标题
DOI：
10.1016/j.geomorph.2004.03.001
复制
发表时间：
2004-10
期刊：
影响因子：
3.9
通讯作者：
M. Kasai;T. Marutani;G. Brierley
中科院分区：
文献类型：
--
作者：
M. Kasai;T. Marutani;G. Brierley
1993年的一场台风导致了日本九州一条陡峭的砾石床山溪--大野武溪沿着的严重淤积。沉积物改造的过程是从一个7年的监测计划，测量调整通道横截面，纵向剖面和基岩露头的范围/分布沿着3公里的研究达到推断。随着时间的推移，该河段采用了浅滩和池结构，河床上的基岩暴露面积显着增加。这种调整过程的特点是逐步减少泥沙储量变化每单位流量。台风引起的扰动后的松弛路径的形状由随后的降雨事件的大小和频率，这些事件的能力，运输可用的沉积物，和到达之间的物理联系。相邻的子河段表现出不同的松弛途径，在响应这些影响，诱导的空间和时间变化的阈值条件沿着通道。长期的证据表明，对主要扰动的反应，如1993年的台风，发生在大约20年的持续时间的“周期”。需要7年的松弛期才能达到准平衡的床层配置和沉积物通量速率。周期的时间范围被认为是反映山坡-河床耦合的变化，标志着产生足够的沉积物储存以重新激活加积和随后退化阶段所需的时间。
A typhoon in 1993 induced major aggradation along Oyabu Creek, a steep, gravel bed mountain stream in Kyushu, Japan. Processes of sediment reworking are inferred from a 7-year monitoring program that measured adjustments to channel cross-sections, the longitudinal profile, and the extent/distribution of bedrock outcrops along a 3-km study reach. Over time, the reach adopted a riffle and pool structure, with notable increase in the area of exposed bedrock on the bed. This adjustment process was characterised by progressive reduction in sediment storage change per unit flow. The relaxation pathway following disturbance induced by the typhoon was shaped by the magnitude and frequency of subsequent rainfall events, the capacity of these events to transport available sediments, and physical linkages between reaches. Adjacent subreaches demonstrated differing relaxation pathways in response to these influences, induced by spatial and temporal variability in threshold conditions along the channel. Longer-term evidence indicates that responses to major disturbance, such as the 1993 typhoon, occur as ‘cycles’ of around 20-year duration. A relaxation period of 7 years is required to attain a quasi-equilibrium bed configuration and rate of sediment flux. The timeframe of cycles is considered to reflect changes to hillslope–channel bed coupling, marking the period required to generate sufficient sediment stores to reactivate phases of aggradation and subsequent degradation.