Mapping the Risk of Soil Erosion in the Medjerda and Mellegue Catchments Using the RUSLE Model, Remote Sensing, and GIS

通過RUSLE模型、遙測以及GIS繪製Medjerda與Mellegure流域的土壤侵蝕風險圖

MENASRIA AMINE ； MEDDI MOHAMED ； HABAIEB HAMADI

《台灣水利》 69卷4期 (2021/12) Pp. 12-39

https://doi.org/10.6937/TWC.202112/PP_69(4).0002

摘要

Soil erosion is a major problem in the Maghreb countries. The consequences of this phenomenon are disastrous, with soil degradation, production of vast areas that are agriculturally sterile, besides agricultural drought conditions aggravated by the increase in runoff compared to infiltration, which leads to a decrease in soil water reserve. This phenomenon may as well cause serious problems of rapid sedimentation of dams. Relevant to this, the present work tries to study the large Medjerda basin located in Algeria and Tunisia, and the Mellegue basin located in Algeria, which contains large agricultural areas and dams used for irrigation as well as drinking water supply. The main objectives of this work are: (1) to estimate the soil erosion rate in Medjerda and Mellegue basins; (2) to highlight the increasing intensity of erosive processes; and (3) to show the effectiveness of some anti-erosion systems existing in the basin. The adopted approach consists in mapping the factors that trigger erosion, using the revised universal soil loss equation integrated with satellite imagery (Landsat Oli8). The obtained results have shown that the average erosion rate in Medjerda and Mellegue is about 13.27 t/ha/year, with 2.1%, 13.6% and 62.12% of the surface of the basin are very sensitive, sensitive and less sensitive to erosion respectively. The obtained results have shown that land management measures and actions are taken to reduce erosion cause a notable decrease of the erosion rate from 14.91 to 8.98 t/ha/year. On the other hand, forest fires increase the rate of erosion by 8%, which is defined, in the erosion class (from 36.17% of the area to 30.85%), as tolerable. The small catchments affected by the fire are the most vulnerable to erosion. The rate of sediment input is about 40% of the average annual rate of soil loss and sediment deposition found in dams in the region. This value can reach 52% in the case of a heavily burnt forest. Improving vegetation density through a combination of reforestation and extension of grazing land has a remarkable effect on the rate of erosion compared to other techniques.

關鍵字

Medjerda catchment ； Normalized Difference Vegetation Index ； Remote sensing ； Revised Universal Soil Loss Equation ； Sediment delivery ratio

並列摘要

土壤侵蝕是馬格里布地區國家都在面臨的主要問題，而該現象則可能帶來災難性的後果，如土壤退化、大片地區無法再生產農作物。此外，與入滲相比，逕流增加會加劇農業乾旱狀況，從而導致土壤儲水量減少。這種現象也可能造成大壩嚴重的淤積頻繁。與此相關，目前的研究試圖探究位於阿爾及利亞和突尼西亞的大範圍Medjerda流域，以及位於阿爾及利亞的Mellegue流域，其中包含大型農業區和用於灌溉和供應飲用水的水壩。本研究旨在（1）估算Medjerda和Mellegue盆地的土壤侵蝕率；（2）強調侵蝕過程中增加的強度；（3）展示流域中存在的一些抗侵蝕系統以及其有效性。本文所採用的方法包括利用修正版通用土壤流失公式結合衛星圖像（Landsat Oli8）繪製引發侵蝕的因素。所得結果表明，Medjerda和Mellegue的平均侵蝕速率約為13.27 t/ha/a，其中2.1%、13.6%和62.12%的盆地表面分別為對侵蝕非常敏感、敏感和較不敏感。結果表明，倘採取土地管理措施和行動以減少侵蝕，則可使侵蝕率從14.91噸／公頃／年顯著下降到8.98噸／公頃／年。另一方面，森林火災使侵蝕率增加8%，而在侵蝕等級（從面積的36.17%到30.85%）中，這種增加被定義為尚可容忍。受火災影響的小集水區最容易受到侵蝕，泥沙輸入率約為該地區水壩年平均土壤流失和泥沙沉積率的40%。在森林被嚴重燒毀的情況下，該值可達到52%。相較於其他技術，通過結合再造林和擴大放牧地以提高植被密度，對侵蝕率會產生顯著影響。

並列關鍵字

邁傑爾達河 ； 常態化差異植生指標（NDVI） ； 遙測 ； 修正版通用土壤流失公式 ； 泥砂輸移比