8.12 Fluvial Processes in Proglacial Environments

AbstractStrong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation.

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The Role of Frost Processes in the Retreat of River Banks

Water ◽

10.3390/w13131812 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1812

Author(s):

Karol Augustowski ◽

Józef Kukulak

Keyword(s):

Relative Role ◽

Freezing And Thawing ◽

Fine Grained ◽

Fluvial Processes ◽

Precise Calculation ◽

Erosion Pins ◽

Summer Half ◽

Lateral Erosion ◽

Summer Flood

The rate of bank retreat was measured using erosion pins on the alluvial banks of the rivers in the Podhale region (the boundary zone between Central and Outer Carpathians) during the hydrological year 2013/2014. During the winter half-year (November–April), the bank retreat was mainly caused by processes related to the freezing and thawing of the ground (swelling, creep, downfall). During the summer half-year (May–October), fluvial processes and mass movements such as lateral erosion, washing out, and sliding predominated. The share of fluvial processes in the total annual amount of bank retreat (71 cm on average) was 4 times greater than that of the frost phenomena. Erosion on bank surfaces by frost phenomena during the cold half-year was greatest (up to 38 cm) on the upper parts of banks composed of fine-grained alluvium, while fluvial erosion during the summer half-year (exceeding 80 cm) mostly affected the lower parts of the banks, composed of gravel. The precise calculation of the relative role of frost phenomena in the annual balance of bank erosion was precluded at some stations by the loss of erosion pins in the summer flood.

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The geomorphic effects of groundwater in introduction to fluvial processes

Journal of Hydrology ◽

10.1016/0022-1694(72)90148-5 ◽

1972 ◽

Vol 16 (4) ◽

pp. 370

Keyword(s):

Fluvial Processes

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Frederick J. Swanson’s 1976–1979 papers on the effects of instream wood on fluvial processes and instream wood management

Progress in Physical Geography Earth and Environment ◽

10.1177/0309133317692411 ◽

2017 ◽

Vol 41 (1) ◽

pp. 124-133 ◽

Cited By ~ 2

Author(s):

Virginia Ruiz-Villanueva ◽

Markus Stoffel

Keyword(s):

Twentieth Century ◽

Historical Review ◽

Knowledge Gaps ◽

River Ecosystems ◽

Fluvial Processes ◽

Fluvial Morphology ◽

The Future ◽

Instream Wood

The recognition of instream wood as a key element of river ecosystems and a driver of fluvial processes is now well established, but it did not start until the second half of the twentieth century. A landmark reference work which led to the development of concepts and methods which are still employed in instream wood studies today was the work by Frederick J. Swanson and his papers published between 1976 and 1979. In this article we revisit these papers, highlighting the pioneering observations about the effects of instream wood on fluvial morphology, the description of the instream wood sources and recruitment processes and the discussion about management of wood in rivers. The instream wood research has grown dramatically since the late 1970s, however many knowledge gaps remain; this short historical review illustrates the importance of continuing and developing those research lines into the future.

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