Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England
Many lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial-interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in...
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ftbruneluniv:oai:bura.brunel.ac.uk:2438/1607 2023-05-15T17:58:22+02:00 Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England Collins, PEF Worsley, P Keith-Lucas, DM Fenwick, IM 53 2006 2499762 bytes application/pdf http://bura.brunel.ac.uk/handle/2438/1607 en eng Elsevier Palaeogeography, Palaeoclimatology, Palaeoecology. 233, 113-133 0031-0182 http://bura.brunel.ac.uk/handle/2438/1607 http://dx.doi.org/10.1016/j.palaeo.2005.09.014 Stadial Interglacial Palaeoecology Peat Tufa Flooding Research Paper 2006 ftbruneluniv https://doi.org/10.1016/j.palaeo.2005.09.014 2021-08-08T08:33:36Z Many lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial-interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in the context of the river Kennet, a tributary of the Thames, since c. 13,000 cal. BP). Some similarities with other rivers are present, suggesting that regional climatic shifts are important controls. The Kennet differs from the regional pattern in a number of ways. The rate of response to sudden climatic change, particularly at the start of the Holocene and also mid-Holocene forest clearance, appears very high. This may reflect abrupt shifts between two catchment scale hydrological states arising from contemporary climates, land use change and geology. Stadial hydrology is dominated by nival regimes, with limited winter infiltration and high spring and summer runoff. Under an interglacial climate, infiltration is more significant. The probable absence of permafrost in the catchment means that a lag between the two states due to its gradual decay is unlikely. Palaeoecology, supported by radiocarbon dates, suggests that, at the very start of the Holocene, a dramatic episode of fine sediment deposition across most of the valley floor occurred, lasting 500-1000 years. A phase of peat accumulation followed as mineral sediment supply declined. A further shift led to tufa deposition, initially in small pools, then across the whole floodplain area, with the river flowing through channels cut in tufa and experiencing repeated avulsion. Major floods, leaving large gravel bars that still form positive relief features on the floodplain, followed mid-Holocene floodplain stability. Prehistoric deforestation is likely to be the cause of this flooding, inducing a major environmental shift with significantly increased surface runoff. Since the Bronze Age, predominantly fine sediments were deposited along the valley with apparently stable channels and vertical floodplain accretion associated with soil erosion and less catastrophic flooding. The Kennet demonstrates that, while a general pattern of river behaviour over time, within a region, may be identifiable, individual rivers are likely to diverge from this. Consequently, it is essential to understand catchment controls, particularly the relative significance of surface and subsurface hydrology. Report permafrost Brunel University London: Brunel University Research Archive (BURA) Palaeogeography, Palaeoclimatology, Palaeoecology 233 1-2 113 133 |
institution |
Open Polar |
collection |
Brunel University London: Brunel University Research Archive (BURA) |
op_collection_id |
ftbruneluniv |
language |
English |
topic |
Stadial Interglacial Palaeoecology Peat Tufa Flooding |
spellingShingle |
Stadial Interglacial Palaeoecology Peat Tufa Flooding Collins, PEF Worsley, P Keith-Lucas, DM Fenwick, IM Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England |
topic_facet |
Stadial Interglacial Palaeoecology Peat Tufa Flooding |
description |
Many lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial-interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in the context of the river Kennet, a tributary of the Thames, since c. 13,000 cal. BP). Some similarities with other rivers are present, suggesting that regional climatic shifts are important controls. The Kennet differs from the regional pattern in a number of ways. The rate of response to sudden climatic change, particularly at the start of the Holocene and also mid-Holocene forest clearance, appears very high. This may reflect abrupt shifts between two catchment scale hydrological states arising from contemporary climates, land use change and geology. Stadial hydrology is dominated by nival regimes, with limited winter infiltration and high spring and summer runoff. Under an interglacial climate, infiltration is more significant. The probable absence of permafrost in the catchment means that a lag between the two states due to its gradual decay is unlikely. Palaeoecology, supported by radiocarbon dates, suggests that, at the very start of the Holocene, a dramatic episode of fine sediment deposition across most of the valley floor occurred, lasting 500-1000 years. A phase of peat accumulation followed as mineral sediment supply declined. A further shift led to tufa deposition, initially in small pools, then across the whole floodplain area, with the river flowing through channels cut in tufa and experiencing repeated avulsion. Major floods, leaving large gravel bars that still form positive relief features on the floodplain, followed mid-Holocene floodplain stability. Prehistoric deforestation is likely to be the cause of this flooding, inducing a major environmental shift with significantly increased surface runoff. Since the Bronze Age, predominantly fine sediments were deposited along the valley with apparently stable channels and vertical floodplain accretion associated with soil erosion and less catastrophic flooding. The Kennet demonstrates that, while a general pattern of river behaviour over time, within a region, may be identifiable, individual rivers are likely to diverge from this. Consequently, it is essential to understand catchment controls, particularly the relative significance of surface and subsurface hydrology. |
format |
Report |
author |
Collins, PEF Worsley, P Keith-Lucas, DM Fenwick, IM |
author_facet |
Collins, PEF Worsley, P Keith-Lucas, DM Fenwick, IM |
author_sort |
Collins, PEF |
title |
Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England |
title_short |
Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England |
title_full |
Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England |
title_fullStr |
Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England |
title_full_unstemmed |
Floodplain environmental change during the younger dryas and holocene: Evidence from the lower kennet valley, south central England |
title_sort |
floodplain environmental change during the younger dryas and holocene: evidence from the lower kennet valley, south central england |
publisher |
Elsevier |
publishDate |
2006 |
url |
http://bura.brunel.ac.uk/handle/2438/1607 |
op_coverage |
53 |
genre |
permafrost |
genre_facet |
permafrost |
op_source |
http://dx.doi.org/10.1016/j.palaeo.2005.09.014 |
op_relation |
Palaeogeography, Palaeoclimatology, Palaeoecology. 233, 113-133 0031-0182 http://bura.brunel.ac.uk/handle/2438/1607 |
op_doi |
https://doi.org/10.1016/j.palaeo.2005.09.014 |
container_title |
Palaeogeography, Palaeoclimatology, Palaeoecology |
container_volume |
233 |
container_issue |
1-2 |
container_start_page |
113 |
op_container_end_page |
133 |
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1766166959224782848 |