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Can channel banks be the dominant source of fine sediment in a UK river?: an example using 137 Cs to interpret sediment yield and sediment source
Author(s) -
Pulley Simon,
Foster Ian
Publication year - 2016
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.4005
Subject(s) - sediment , drainage basin , hydrology (agriculture) , sedimentary budget , floodplain , channel (broadcasting) , geology , provenance , environmental science , sediment transport , geomorphology , geochemistry , geography , cartography , geotechnical engineering , engineering , electrical engineering
Cultivated fields have been shown to be the dominant sources of sediment in almost all investigated UK catchments, typically contributing 85 to 95% of sediment inputs. As a result, most catchment management strategies are directed towards mitigating these sediment inputs. However, in many regions of the UK such as the Nene basin there is a paucity of sediment provenance data. This study used the caesium‐137 ( 137 Cs) inventories of lake and floodplain cores as well as the 137 Cs activities of present day sediment to determine sediment provenance. Sediment yields were also reconstructed in a small lake catchment. Low 137 Cs inventories were present in the lake and floodplain cores in comparison to the reference inventory and inventories in cores from other UK catchments. Caesium‐137 activities in the present day sediments were low; falling close to those found in the channel bank catchment samples. It was estimated that 60 to 100% of the sediment in the Nene originated from channel banks. Pre‐1963 sediment yields were approximately 11.2 t km − 2 yr −1 and post‐1963 was approximately 11.9 t km − 2 yr −1 . The lack of increased sediment yield post‐1963 and low sediment yield is unusual for a UK catchment (where a yield of 28 to 51 t km − 2 yr −1 is typical for a lowland agricultural catchment), but is explained by the low predicted contribution of sediment from agricultural topsoils. The high channel bank contribution is likely caused by the river being starved of sediment from topsoils, increasing its capacity to entrain bank material. The good agreement between the results derived using cores and recently transported sediments, highlight the reliability of 137 Cs when tracing sediment sources. However, care should be taken to assess the potential impacts of sediment particle size, sediment focusing in lakes and the possible remobilization of 137 Cs from sedimentary deposits. Copyright © 2016 John Wiley & Sons, Ltd.