{"title":"Geomorphological evidence of a historical Landslide-dammed Lake Outburst Flood in the Cajón del Bayo basin, Southern Central Andes (36°S)","authors":"Mariana Correas-Gonzalez , Stella M. Moreiras , Carolina Lauro , Pilar Jeanneret","doi":"10.1016/j.jsames.2025.105710","DOIUrl":null,"url":null,"abstract":"<div><div>Landslide dammed lakes are created when mass movements block river valleys, posing potential hazards in the form of Landslide-dammed Lake Outburst Flood (LLOF). In the Southern Central Andes (SCA) of Argentina (36°S), a rock avalanche dammed the Cajón del Bayo basin in 1986, creating Baya Lake. This study reconstructs the historical evolution of the basin, focusing on key geomorphological changes including the rock avalanche, lake formation and subsequent outburst flood. The analysis included: a) a geomorphological mapping, identification of outburst flood deposits and remote sensing of landscape evolution; b) sedimentological description of landslide facies and lake-level variations; c) landslide-dam characterisation and stability assessment; and d) a hydrometeorological analysis of temperature and precipitation to contextualise the LLOF event. Results show that a 4.7 hm<sup>3</sup> rock avalanche impounded the Baya Lake. Geomorphic stability indices yielded contrasted results: while one classified the dam as stable, another indicated instability. Ultimately, the dam collapsed, triggering a LLOF that released 0.14 hm<sup>3</sup> of water from the lake and 0.3 hm<sup>3</sup> of sediments eroded from the dam, exposing its internal structure. Although geomorphic impacts were evident immediately downstream the lake, the event was not detected at the nearest gauging station, and a regional flood frequency analysis indicate low probability of occurrence of the empirically estimated peak discharge. This highlights how LLOFs occurred in remote areas may go unnoticed and how the increased discharge from small tributaries, though significant locally, can be attenuated in larger rivers. These findings underscore the importance of identifying and studying LLOFs at both local and regional scales in the SCA, where such events are underreported and may differ from global cases.</div></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":"165 ","pages":"Article 105710"},"PeriodicalIF":1.5000,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of South American Earth Sciences","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0895981125003724","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Landslide dammed lakes are created when mass movements block river valleys, posing potential hazards in the form of Landslide-dammed Lake Outburst Flood (LLOF). In the Southern Central Andes (SCA) of Argentina (36°S), a rock avalanche dammed the Cajón del Bayo basin in 1986, creating Baya Lake. This study reconstructs the historical evolution of the basin, focusing on key geomorphological changes including the rock avalanche, lake formation and subsequent outburst flood. The analysis included: a) a geomorphological mapping, identification of outburst flood deposits and remote sensing of landscape evolution; b) sedimentological description of landslide facies and lake-level variations; c) landslide-dam characterisation and stability assessment; and d) a hydrometeorological analysis of temperature and precipitation to contextualise the LLOF event. Results show that a 4.7 hm3 rock avalanche impounded the Baya Lake. Geomorphic stability indices yielded contrasted results: while one classified the dam as stable, another indicated instability. Ultimately, the dam collapsed, triggering a LLOF that released 0.14 hm3 of water from the lake and 0.3 hm3 of sediments eroded from the dam, exposing its internal structure. Although geomorphic impacts were evident immediately downstream the lake, the event was not detected at the nearest gauging station, and a regional flood frequency analysis indicate low probability of occurrence of the empirically estimated peak discharge. This highlights how LLOFs occurred in remote areas may go unnoticed and how the increased discharge from small tributaries, though significant locally, can be attenuated in larger rivers. These findings underscore the importance of identifying and studying LLOFs at both local and regional scales in the SCA, where such events are underreported and may differ from global cases.
山体滑坡堰塞湖是在山体运动阻塞河谷的情况下形成的,具有山体滑坡堰塞湖溃决洪水的潜在危害。在阿根廷安第斯山脉的中南部(SCA)(36°S), 1986年的一次岩石雪崩阻塞了Cajón del Bayo盆地,形成了Baya湖。本研究重建了该盆地的历史演化,重点研究了岩崩、湖泊形成和溃决洪水等关键地貌变化。分析内容包括:a)地貌制图、溃决洪水沉积物识别和景观演变遥感;B)滑坡相和湖面变化的沉积学描述;C)滑坡坝特征及稳定性评价;d)对温度和降水进行水文气象分析,以了解lof事件的背景。结果表明,巴雅湖发生4.7 hm3的岩崩淤塞。地貌稳定性指数得出了截然相反的结果:一项将大坝归为稳定,另一项则表示不稳定。最终,大坝坍塌,引发了一场大洪水,湖中释放了0.14立方厘米的水,大坝侵蚀了0.3立方厘米的沉积物,暴露了大坝的内部结构。虽然湖泊下游的地貌影响很明显,但最近的测量站没有检测到这一事件,区域洪水频率分析表明,经验估计的洪峰流量发生的可能性很低。这凸显了在偏远地区发生的低水位淤积如何可能被忽视,以及小支流的流量增加如何在较大的河流中减弱,尽管在当地意义重大。这些发现强调了在SCA的地方和区域尺度上识别和研究LLOFs的重要性,这些事件被低估了,并且可能与全球病例不同。
期刊介绍:
Papers must have a regional appeal and should present work of more than local significance. Research papers dealing with the regional geology of South American cratons and mobile belts, within the following research fields:
-Economic geology, metallogenesis and hydrocarbon genesis and reservoirs.
-Geophysics, geochemistry, volcanology, igneous and metamorphic petrology.
-Tectonics, neo- and seismotectonics and geodynamic modeling.
-Geomorphology, geological hazards, environmental geology, climate change in America and Antarctica, and soil research.
-Stratigraphy, sedimentology, structure and basin evolution.
-Paleontology, paleoecology, paleoclimatology and Quaternary geology.
New developments in already established regional projects and new initiatives dealing with the geology of the continent will be summarized and presented on a regular basis. Short notes, discussions, book reviews and conference and workshop reports will also be included when relevant.