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Human impact on the change of direction of river channel migration caused by formation of a landslide dam

Cebulski J.

Studia Geomorphologica Carpatho-Balcanica

2016

Vol. 50

5--17

The paper presents the impact of man on the change of direction of the natural migration of a stream channel resulting from triggering a landslide on stream bank. The landslide that was formed on 15th May 2014 in the Łapsze Niżne village led to the formation of a landslide dam and a small dam lake upstream of it. Waters flowed over the surface of the fill terrace and returned to the old channel, approximately 120 m downstream the landslide. Following 33 days of the landslide activation, the dam was cut, and material was removed and deposited within the channel meander downstream. This caused the waters of the Łapszanka stream to return to the cleared channel. Three series of measurements were performed using a terrestrial laser scanner (TLS). The TLS made possible to calculate the volume of the landslide tongue (1,690m³) and the maximum volume of the material forming the landslide dam for which the flow of the waters of the Łapszanka stream would remain within the old channel (761 m³). Exceeding this value led to diverting the stream waters towards the fill terrace. Thereby, the process of forming a new channel was commenced. During its functioning (33 days), material of a volume of 55 m³ was eroded. Lack of human intervention in the natural process of migration of the channel would result in continuous removal of material from the terrace and formation of a new channel.

Quantitative changes in near-channel landslides caused by fluvial erosion in the light of high-resolution DEM

Cebulski Jarosław

Studia Geomorphologica Carpatho-Balcanica

2022/2023

Vol. 56/57

3--50

The article deals the issue of near-channel landslide activity in two regions (Rożnowskie Foothills and Beskid Niski Mountains) in the Polish Outer Carpathians. The main objective of the research was to determine the volume of material removed from the studied landslides in the period from their occurrence to 2012 and to compare these results with the volume of material removed from landslides during the period of detailed research in 2014–2017. The ALS data was used to prepared to the DoDs analysis DoD analysis with theoretical landslide surfaces and to determine the volume of material removed from the occurrence of landslides to 2012. Detailed TLS surveys (10 measurement series) were carried out from April 2014 to November 2017, resulting in nine Digital Elevation Models (DEMs) of Difference (DoDs), illustrating quantitative and spatial changes within the investigated landslides. It was found that near-channel landslides, under the influence of ongoing fluvial erosion, exhibit continuous activity with varying intensity, depending on the hydrometeorological conditions. During flood events, the movements within the entire landslide area were activated. Conversely, in periods between floods, there was a constant removal of material from the toe of the landslides. During flood events, the material carried away by streams accounted for 60% to 90% of the volume of material removed throughout the research period. The volume of material removed from the landslide in 4 years of survey ranges from 14 to 107% of the material removed from the landslide since its occurrence to 2012.