Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 431551
Title Upstream and downstream controls of recent avulsions on the Taquari megafan, Pantanal, south-western Brazil
Author(s) Makaske, B.; Maathuis, B.H.P.; Padovani, C.R.; Stolker, C.; Mosselman, E.; Jongman, R.H.G.
Source Earth Surface Processes and Landforms 37 (2012)12. - ISSN 0197-9337 - p. 1313 - 1326.
DOI http://dx.doi.org/10.1002/esp.3278
Department(s) Alterra - Soil geography
Alterra - Biodiversity and policy
Publication type Refereed Article in a scientific journal
Publication year 2012
Keyword(s) rhine-meuse delta - upper columbia river - british-columbia - channel belts - bighorn basin - netherlands - floodplain - deposits - architecture - aggradation
Abstract Avulsion, the natural relocation of a river, is a key process in the evolution of subaerial fans, river floodplains and deltas. The causes of avulsion are poorly understood, which is partly due to the scarcity of field studies of present avulsions. At present, two avulsions are occurring on the middle and lower Taquari megafan, Pantanal basin, south-western Brazil. Here we present an analysis of the causes of these avulsions based on field and remote sensing data and show that avulsions on megafans can be controlled by both upstream and downstream processes. The middle fan avulsion (started in 1997–1998) is a result of upstream control: overbank aggradation was caused by the (variable) input of sandy sediment into the system, which caused channel-belt superelevation and also created an easily erodible subsurface favouring bank retreat, crevassing, and scour of deep floodplain channels. The sandy subsurface in this area is inferred to have been a major factor in the causation of this avulsion under conditions of little gradient advantage. The lower fan avulsion (started c. 1990) results from interplay of upstream and downstream controls, the latter being related to the local base level (the Paraguay River floodplain) at the toe of the fan. Channel and overbank aggradation on the lower fan was influenced by fan sub-lobe progradation and channel backfilling. Fan sub-lobe progradation caused a significant gradient advantage of the avulsion channel over the parent channel. Avulsions are commonly supposed to be preferentially triggered by high-magnitude floods, when there is considerable channel-belt superelevation. However, both avulsions studied by us were triggered by small to average floods, with modest channel-belt superelevation. We conclude that flood magnitude and channel-belt superelevation have been overrated as causes of avulsion, and demonstrate additional causes that influence the growth of crevasses into avulsions.
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