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Convergent human and climate forcing of late-Holocene flooding in Northwest England

Convergent human and climate forcing of late-Holocene flooding in Northwest England
Convergent human and climate forcing of late-Holocene flooding in Northwest England

Concern is growing that climate change may amplify global flood risk but short hydrological data series hamper hazard assessment. Lake sediment reconstructions are capturing a fuller picture of rare, high-magnitude events but the UK has produced few lake palaeoflood records. We report the longest lake-derived flood reconstruction for the UK to date, a 1500-year record from Brotherswater, northwest England. Its catchment is well-suited physiographically to palaeoflood research, but its homogeneous, dark brown sediment matrix precludes visual identification of flood layers. Instead, an outlier detection routine applied to high-resolution particle size measurements showed a >90% match, in stratigraphic sequence, to measured high river flows. Our late-Holocene palaeoflood reconstruction reveals nine multi-decadal periods of more frequent flooding (510–630 CE, 890–960, 990–1080, 1470–1560, 1590–1620, 1650–1710, 1740–1770, 1830–1890 and 1920–2012), and these show a significant association with negative winter North Atlantic Oscillation (wNAO) phasing and some synchrony with solar minima. These flood-rich episodes also overlap with local and regional land-use intensification, which we propose has amplified the flood signal by creating a more efficient catchment sediment conveyor and more rapid hillslope-channel hydrological connectivity. Disentangling anthropogenic and climatic drivers is a challenge but anthropogenic landscape transformation should evidently not be underestimated in palaeoflood reconstructions. Our paper also demonstrates that flood histories can be extracted from the numerous lakes worldwide containing organic-rich, visually homogeneous sediments. This transformative evidence base should lead to more reliable assessments of flood frequency and risks to ecosystems and infrastructure.

Flood hazard, Human activity, Lake sediments, North Atlantic Oscillation, Paleofloods, Solar forcing
0921-8181
Schillereff, D.N.
6c919084-6869-4735-85ad-2c2dbc5f07a6
Chiverrell, R.C.
193e87d2-aae0-499c-b92b-af07eb2a494d
Macdonald, N.
56fc19d1-88f0-44dc-90ae-c5d670b90da4
Hooke, J.M.
130577d2-a7c9-465c-997f-47c0b5ad380a
Welsh, K. E.
926e0d3a-86fe-420e-96f4-526ed58d89a0
Piliposian, G.
95eb7b6b-055e-4b6e-8a9b-829abffd2644
Croudace, I.W.
24deb068-d096-485e-8a23-a32b7a68afaf
Schillereff, D.N.
6c919084-6869-4735-85ad-2c2dbc5f07a6
Chiverrell, R.C.
193e87d2-aae0-499c-b92b-af07eb2a494d
Macdonald, N.
56fc19d1-88f0-44dc-90ae-c5d670b90da4
Hooke, J.M.
130577d2-a7c9-465c-997f-47c0b5ad380a
Welsh, K. E.
926e0d3a-86fe-420e-96f4-526ed58d89a0
Piliposian, G.
95eb7b6b-055e-4b6e-8a9b-829abffd2644
Croudace, I.W.
24deb068-d096-485e-8a23-a32b7a68afaf

Schillereff, D.N., Chiverrell, R.C., Macdonald, N., Hooke, J.M., Welsh, K. E., Piliposian, G. and Croudace, I.W. (2019) Convergent human and climate forcing of late-Holocene flooding in Northwest England. Global and Planetary Change, 182, [102998]. (doi:10.1016/j.gloplacha.2019.102998).

Record type: Article

Abstract

Concern is growing that climate change may amplify global flood risk but short hydrological data series hamper hazard assessment. Lake sediment reconstructions are capturing a fuller picture of rare, high-magnitude events but the UK has produced few lake palaeoflood records. We report the longest lake-derived flood reconstruction for the UK to date, a 1500-year record from Brotherswater, northwest England. Its catchment is well-suited physiographically to palaeoflood research, but its homogeneous, dark brown sediment matrix precludes visual identification of flood layers. Instead, an outlier detection routine applied to high-resolution particle size measurements showed a >90% match, in stratigraphic sequence, to measured high river flows. Our late-Holocene palaeoflood reconstruction reveals nine multi-decadal periods of more frequent flooding (510–630 CE, 890–960, 990–1080, 1470–1560, 1590–1620, 1650–1710, 1740–1770, 1830–1890 and 1920–2012), and these show a significant association with negative winter North Atlantic Oscillation (wNAO) phasing and some synchrony with solar minima. These flood-rich episodes also overlap with local and regional land-use intensification, which we propose has amplified the flood signal by creating a more efficient catchment sediment conveyor and more rapid hillslope-channel hydrological connectivity. Disentangling anthropogenic and climatic drivers is a challenge but anthropogenic landscape transformation should evidently not be underestimated in palaeoflood reconstructions. Our paper also demonstrates that flood histories can be extracted from the numerous lakes worldwide containing organic-rich, visually homogeneous sediments. This transformative evidence base should lead to more reliable assessments of flood frequency and risks to ecosystems and infrastructure.

Full text not available from this repository.

More information

Accepted/In Press date: 25 July 2019
e-pub ahead of print date: 30 July 2019
Published date: 1 November 2019
Keywords: Flood hazard, Human activity, Lake sediments, North Atlantic Oscillation, Paleofloods, Solar forcing

Identifiers

Local EPrints ID: 437497
URI: http://eprints.soton.ac.uk/id/eprint/437497
ISSN: 0921-8181
PURE UUID: 0d52ef7b-dd9d-4588-8c2b-814b79627009

Catalogue record

Date deposited: 31 Jan 2020 17:36
Last modified: 06 Oct 2020 21:09

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