Land use in the Souss region, South Morocco and its influence on wadi dynamics
Land use in the Souss region, South Morocco and its influence on wadi dynamics
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摩洛哥南部苏斯地区的土地利用及其对河道动态的影响
DOI：
10.1127/zfg_suppl/2019/0525
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Aït Hssaine
中科院分区：
文献类型：
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作者：
Kirchhoff;Aït Hssaine
苏地区受到持续的土地利用变化的强烈影响，这种变化伴随着强烈的冲片、细沟和沟壑侵蚀。这些非常高的沉积物量是由被称为wadis或oued的短暂河流收集的。这项研究的目的是确定当前的土地利用和土地利用变化是否会在中期影响河底动态，原因是由于斜坡侵蚀导致河底恶化，或者由于低泥沙负荷或无泥沙负荷的排放导致河底侵蚀。土地使用被绘制为Taroudant北部的整个集水区，这是一个起源于高阿特拉斯的冲积扇。冲刷链用来测量河床上的侵蚀或堆积。在2011年至2014年期间，在7个不同的流域共进行了37次测量。测量结果从+30厘米（积累）到-37厘米（侵蚀）不等，每次测量间隔从两周到一年不等。有些河道以侵蚀为主，有些河道则以堆积为主。从实测数据来看，“冲填”现象较为明显，泥沙从流速较大的河道上冲刷而下，随着流速的减小，淤积物冲刷下游的细沟。控制河道动态的因子主要为地表年变化的“日最大降水量”和河床高程变化的“河道累计长度”、“集水区面积”和“每集水区平均坡度”，而“土地利用”在两者之间的相关性较弱。由于冲刷链代表准时测量，不允许插值到更高的时间空间尺度，本研究只能显示河道内部的趋势。横截面上的侵蚀和堆积以及河道的长度变化很大，这里提出的经验方法似乎有希望接近固有动力学的量化。
The Souss region is strongly influenced by a continuous land use change which is accompanied by strong sheet wash, rill and gully erosion. These very high sediment amounts are collected by ephemeral rivers called wadis or Oueds. This study aimed to determine if the current land uses and land use change influenced wadi dynamics in the medium term by aggradation of the wadi bed due to erosion on the slopes or erosion of the wadi bed because of discharge with low or no sediment loads. The land use was mapped for the entire catchment area north of Taroudant, an alluvial fan originating from the High Atlas. Scour chains were used to measure erosion or accumulation on the wadi bed. During the years 2011- 2014, 37 measurements in total were conducted in seven different wadis. The measurements showed variable results ranging from +30 cm (accumulation) to -37 cm (erosion) per measurement interval ranging from two weeks to one year. While erosion was dominant in some wadis, others showed a tendency towards accumulation. From the measurement data, the phenomenon of 'Scour & Fill' becomes apparent: sediment is eroded from the wadi with high water velocities and fills scour rills downstream with decreasing flow speed. Factors most likely controlling wadi dynamics were "daily maximum precipitation" for yearly surface changes and "accumulated wadi length", "catchment area" and "mean slope per catchment" for the change in bed elevation since the installation of the scour chain, while "land use" showed less correlation in both aspects. Since scour chains represent punctual measurements which do not allow for an interpolation to higher tempo-spatial scales, this study can only show trends inside a wadi. Erosion and accumulation in the cross-section as well as over the length of a wadi can vary greatly, and the here presented empirical method seems promising for approaching the quantification of inherent dynamics.