Spatial distribution of gully head activity and sediment supply along an ephemeral channel in a Mediterranean environment
Spatial distribution of gully head activity and sediment supply along an ephemeral channel in a Mediterranean environment
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DOI：
10.1016/s0341-8162(99)00092-2
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发表时间：
2000-04
期刊：
影响因子：
6.2
通讯作者：
D. O. Wijdenes;J. Poesen;L. Vandekerckhove;M. Ghesquiére
中科院分区：
文献类型：
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作者：
D. O. Wijdenes;J. Poesen;L. Vandekerckhove;M. Ghesquiére
在这项研究中，我们研究了控制的因素，银行沟头沿着到达一个短暂的河流（兰布拉萨拉达）在西班牙东南部的荒漠化威胁的地区。458沟头的活动进行了评估，在现场预定义的标准，如锋利的边缘，存在的水垫塘，张力裂缝，最近沉积的沉积物，流痕，植被再生长。结果表明，土地利用方式对河岸沟头活动有显著影响。最近的土地利用变化，包括杏仁种植的扩展似乎加强银行沟头活动。岩性对岸沟的扩展也有明显的影响。进一步调查了沟头是否是水库淤积的重要泥沙来源。（非常）活跃的银行沟头沿着研究达到的密度是每17米的渠道长度。年平均退水量来自46个活跃沟头（4.0 m3y−1）的测量结果。通过选择Puentes水库集水区的所有渠道部分，使用航空照片，建立了全流域的银行沟头的泥沙产量的估计。据估计，仅在12，760公顷的研究区域（占Puentes水库总集水面积的12%）中，活动河岸沟头的退缩就产生了6%的沉积物填充水库。考虑到沉积物也来自其他来源，如渠道壁，渠道床，和山坡，总体结论是，在西班牙东南部的银行冲沟扩张是一个主要的点源沉积物，因此，土地退化的主要过程。
In this study, we examined the factors that control the spatial distribution of bank gully heads along a reach of an ephemeral river (Rambla Salada) in an area threatened by desertification in Southeast Spain. The activity of 458 gully heads was assessed in the field by pre-defined criteria such as sharp edges, presence of a plunge pool, tension cracks, recent deposited sediments, flow marks, and vegetation re-growth. The results showed that land use has a significant impact on bank gully head activity. Recent land-use changes involving the extension of almond cultivation appears to intensify bank gully head activity. Also, lithology has a clear impact on the bank gully extension. It was further investigated whether the gully heads were important sediment sources that contributed to reservoir sedimentation. The density of (very) active bank gully heads along the study reach was one per 17 m of channel length. Average annual retreat volumes were derived from measurements at 46 active gully heads (4.0 m3y−1). By selecting all the channel sections in the catchment of the Puentes Reservoir with a similar pattern of bank gullies using aerial photographs, an estimate of basin-wide sediment production of bank gully heads was established. It was estimated that the retreat of active bank gully heads alone in the 12,760 ha study area (representing 12% of the total catchment area of the Puentes Reservoir) produced 6% of the sediment filling up the reservoir. Considering that the sediment is also derived from other sources such as channel walls, channel beds, and hillslopes, the overall conclusion is that bank gully expansion in Southeast Spain is a major point source of sediment and therefore, a major process of land degradation.