High rates of sediment yield in the southern Ethiopian highlands and the role of alluvial fans in regulating sediment delivery to Rift Valley Lakes

IF 5.4 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena Pub Date : 2025-04-27 DOI:10.1016/j.catena.2025.109068

Alemayehu Kasaye Tilahun , Francis Matthews , Margaret Chen , Guchie Gulie , Gert Verstraeten

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引用次数: 0

Abstract

Here, we evaluate the suspended sediment yield and its spatial variability along the fluvial system of two tropical mountainous catchments (Elgo and Shafe) which drain into Lake Abaya and Lake Chamo in the southern Ethiopian Rift Valley. We quantified the sediment yield from continuous discharge measurements at six gauging stations during the rainy seasons of three consecutive years from April 2018 to December 2020, and using season-specific sediment rating curves developed based on 1938 suspended sediment samples. The average area-specific sediment yield (SSY) ranges from 1,887 to 19,517t km⁻² a⁻¹ for catchments ranging between 46 and 298 km², which is very high by world standards. Whilst SSY increases with catchment area in the highlands itself, an important decrease in SSY is observed in the lowland areas. The large alluvial fan complexes of Elgo and Shafe trap ∼ 40 % and 60 % of the sediment delivered to the apex of the fans, respectively. The alluvial fans thus significantly reduce the amount of sediment delivered from the eroding highlands to the Rift Valley lakes and act as important sediment sink in the catchment’s sediment budget.

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埃塞俄比亚南部高地的高产沙率和冲积扇在调节向裂谷湖泊输送沉积物中的作用

在这里，我们评估了两个热带山地集水区（Elgo和Shafe）沿河流系统的悬沙产量及其空间变异，这两个集水区流入埃塞俄比亚南部大裂谷的Abaya湖和Chamo湖。在2018年4月至2020年12月连续3年的雨季期间，通过6个测量站的连续流量测量，使用基于1938个悬沙样本的特定季节泥沙等级曲线，对产沙量进行了量化。在46 ~ 298 km2的流域，平均面积比产沙量（SSY）在1887 ~ 19517 t km−2 a−1之间，以世界标准衡量是非常高的。虽然在高地本身，随着集水区面积的增加，SSY增加，但在低地地区，SSY明显减少。埃尔戈（Elgo）和谢夫（Shafe）的大型冲积扇复合体分别将40%和60%的沉积物截留到扇的顶端。冲积扇因此大大减少了从侵蚀高地向裂谷湖泊输送的泥沙量，并在流域的泥沙收支中扮演重要的泥沙汇的角色。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Catena 环境科学-地球科学综合

CiteScore

10.50

自引率

9.70%

发文量

816

审稿时长

54 days

期刊介绍： Catena publishes papers describing original field and laboratory investigations and reviews on geoecology and landscape evolution with emphasis on interdisciplinary aspects of soil science, hydrology and geomorphology. It aims to disseminate new knowledge and foster better understanding of the physical environment, of evolutionary sequences that have resulted in past and current landscapes, and of the natural processes that are likely to determine the fate of our terrestrial environment. Papers within any one of the above topics are welcome provided they are of sufficiently wide interest and relevance.