Adjustments in channel form, sediment calibre and vegetation around check‐dams in the headwater reaches of mountain torrents, Calabria, Italy
Adjustments in channel form, sediment calibre and vegetation around check‐dams in the headwater reaches of mountain torrents, Calabria, Italy
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DOI：
10.1002/esp.1791
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发表时间：
2009-06
影响因子：
3.3
通讯作者：
G. Bombino;A. Gurnell;V. Tamburino;D. Zema;S. M. Zimbone
中科院分区：
文献类型：
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作者：
G. Bombino;A. Gurnell;V. Tamburino;D. Zema;S. M. Zimbone
河谷底部植被的结构和动态与河流过程和地貌动态密切相关。所有这些联系都因工程控制工程的安装而中断。我们使用以前开发的调查和分析方法，调查在意大利南部卡拉布里亚陡峭的季节性流动溪流(Fiumaras)的受限源头安装淤地坝对活跃河道形态、沉积物口径以及河岸植被丰富度、覆盖度和发展的影响。根据跨活动航道断面的详细野外测量，获得了紧邻上游(U)的60个断面的植被程度指数(GCC)、发育指数(WCH)及其横断面变异系数(两个指数在每个调查点的变异系数)、存在的物种数量(NS)、航道形状(宽/深比)、横截面积(CSA)、下游坡度(坡度)、表层底沙口径(D50)和地下细泥沙含量(按重量计小于250微米的百分比)。下游(D)和中间地点(I)大约20个淤地坝分布在四个不同的源头集水区。对这一数据集的分析表明，淤地坝上游河道形态和泥沙口径在统计上的显著变化与活跃河道上更一致的植被发展有关，包括相对于其他横断面物种丰富度的增加，但只有在河道的物理特征与中下游河道显著不同的情况下，才会出现植被覆盖和发育的显著增加。由于研究洪流具有天然陡峭的剖面，淤地坝之间的中间段在形态上往往更类似于位于淤地坝下游的河道，而不是位于上游的河道，从而导致河岸植被具有相似的结构特性。与下游相比，中间断面支持的物种要多得多，但淤地坝上游的条件似乎非常有利于河岸植被的发展，以至于物种丰富度超过了中游。尽管源头位置有限，但在研究流域内，淤地坝周围在形态、沉积物和植被发展方面的这些对比是强烈和一致的，超过了流域之间在物种丰富度和沉积物口径方面的更微妙的对比。版权所有©2009 John Wiley&Sons，Ltd.
The structure and dynamics of vegetation in valley bottoms are both strongly associated with fluvial processes and landform dynamics. All of these associations are disrupted by the installation of engineering control works. We use survey and analysis methods developed previously to investigate the impact of the installation of check‐dams within the confined headwaters of steep seasonally‐flowing streams (fiumaras) in Calabria, southern Italy, on active channel form, sediment calibre, and the richness, cover and development of riparian vegetation. Based on detailed field measurements along transects across the active channel, estimates of indices of vegetation extent (GCC), development (WCH) and their cross‐sectional variability (coefficients of variation of both indices at each survey site CVGCC, CVWCH), the number of species present (Ns), channel shape (w/d – the width/depth ratio), cross‐sectional area (CSA), downstream gradient (slope), surface bed sediment calibre (D50) and subsurface fine sediment content (percentage less than 250 µm by weight) were obtained for 60 transects located immediately upstream (U), downstream (D) and at intermediate sites (I) around 20 check‐dams located in four different headwater catchments. Analysis of this data set suggests that statistically significant changes in channel form and sediment calibre upstream of check‐dams are associated with more consistent vegetation development across the active channel, including an increase in species richness relative to other transects, but notable increases in vegetation cover and development only arise where the physical characteristics of the channel are notably different from intermediate and downstream channels. Because of the naturally steep profile of the study torrents, intermediate sections between check‐dams tend to be more similar in form to channels located immediately downstream of check‐dams than those located upstream, leading to similar structural properties in the riparian vegetation. The intermediate transects support considerably more species than downstream reaches, but the conditions upstream of the check‐dams appear to be so favourable for riparian vegetation development that species richness exceeds that found in intermediate reaches. Despite the confined headwater locations, these contrasts in form, sediment and vegetation development around check‐dams are strong and consistent across the study catchments, over‐riding more subtle contrasts in species richness and sediment calibre between catchments. Copyright © 2009 John Wiley & Sons, Ltd.