Characteristics of channel steps and reach morphology in headwater streams, southeast Alaska
Characteristics of channel steps and reach morphology in headwater streams, southeast Alaska
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阿拉斯加东南部源头河流的河道台阶和河段形态特征
DOI：
10.1016/s0169-555x(02)00338-0
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发表时间：
2003
期刊：
影响因子：
3.9
通讯作者：
M. Bryant
中科院分区：
文献类型：
--
作者：
T. Gomi;R. Sidle;R. Woodsmith;M. Bryant
在阿拉斯加东南部的16条源头溪流中，研究了木材采伐和质量移动对河道台阶和河段形态的影响。由木质碎屑和巨石形成的河道台阶是源头溪流中重要的河道单元。台阶的数量、间隔和高度在不同的管理和干扰制度中没有区别。现代滑坡河道和老河道的河段(单位坡度为0.25)，河道坡度与平均步距呈指数负相关。在以堆积作用为主的上游(≥-0.25梯度)，没有发现这种关系。来自再生河岸林分的木质碎屑和沉积物的吸收可能掩盖了幼龄赤杨、幼龄针叶树和最近被砍伐的河道中台阶几何形状和河道坡度之间的任何强烈关系。河道河段被描述为水池冲刷、阶梯、阶梯、瀑布、急流和基岩。河道台阶的几何形状主要表征河道河段类型。推论河床冲刷和台阶滩河段以河流过程为主，基岩河段以堆积过程为主。阶梯、急流和梯级河段出现在以河流和堆积过程为主的河道中。梯级河段是从梯级(上游)向梯级池河段(下游)过渡的。从河岸走廊和伐木活动中吸收的木质碎屑形成台阶，然后可能依次将河道河段类型从台阶塘改变为台阶。滑坡和泥石流引起的泥沙和木质碎屑的冲刷、冲刷和沉积改变了河段类型(基岩、梯级和台阶塘)的分布和河段内台阶的结构。
The effect of timber harvesting and mass movement on channel steps and reach morphology was examined in 16 headwater streams of SE Alaska. Channel steps formed by woody debris and boulders are significant channel units in headwater streams. Numbers, intervals, and heights of steps did not differ among management and disturbance regimes. A negative exponential relationship between channel gradient and mean length of step intervals was observed in the fluvial reaches (<0.25 unit gradient) of recent landslide and old-growth channels. No such relationship was found in upper reaches (≥0.25 gradient) where colluvial processes dominated. Woody debris and sediment recruitment from regenerating riparian stands may have obscured any strong relationship between step geometry and channel gradient in young alder, young conifer, and recent clear-cut channels. Channel reaches are described as pool–riffles, step–pools, step–steps, cascades, rapids, and bedrock. Geometry of channel steps principally characterized channel reach types. We infer that fluvial processes dominated in pool–riffle and step–pool reaches, while colluvial processes dominated in bedrock reaches. Step–step, rapids, and cascade reaches occurred in channels dominated by both fluvial processes and colluvial processes. Step–step reaches were transitional from cascades (upstream) to step–pool reaches (downstream). Woody debris recruited from riparian corridors and logging activities formed steps and then sequentially might modify channel reach types from step–pools to step–steps. Scour, runout, and deposition of sediment and woody debris from landslides and debris flows modified the distribution of reach types (bedrock, cascade, and step–pool) and the structure of steps within reaches.