A large floodplain of the River Findhorn, northeast Scotland, was investigated using hydrogeological and hydrochemical methods (including residence time indicators) to characterise groundwater/surface-water coupling and groundwater flooding. The study demonstrated widespread stratification within the floodplain: shallow (<8 mbgl) deposits are highly permeable (100 m/d); deeper deposits have low permeability (1 m/d) and limit interaction with the underlying sandstone aquifer. Hydrochemistry and groundwater-level variations show floodplain groundwater is recharged from the river, surrounding hillslopes and direct rainfall infiltration. The river loses water to groundwater as it enters the floodplain; further downstream, groundwater response follows closely river stage giving rise to complex exchanges; near the sea, groundwater continually discharges to rivers, tributaries and ditches. Groundwater flow is largely parallel to the river and mean groundwater residence times vary from 3 years to 20 years. Groundwater at the edge of the floodplain, close to the hillslopes, has distinctive chemistry and responds rapidly to local intense rainfall (daily total >30 mm). Persistent groundwater flooding occurs within topographical lows and also in the discharge zone where it is largely managed with a series of drains constructed in the 19th century. The significant and complex role of groundwater in floodplains, demonstrated by this study, highlights the importance of fully considering groundwater in flood management schemes.
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Research Article|
February 20 2014
Groundwater, flooding and hydrological functioning in the Findhorn floodplain, Scotland
A. M. MacDonald;
1British Geological Survey, Murchison House, Edinburgh EH9 3LA, UK
E-mail: [email protected]
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D. J. Lapworth;
D. J. Lapworth
2British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
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A. G. Hughes;
A. G. Hughes
3British Geological Survey, Keyworth, Nottingham, UK
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C. A. Auton;
C. A. Auton
1British Geological Survey, Murchison House, Edinburgh EH9 3LA, UK
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L. Maurice;
L. Maurice
2British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
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A. Finlayson;
A. Finlayson
1British Geological Survey, Murchison House, Edinburgh EH9 3LA, UK
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D. C. Gooddy
D. C. Gooddy
2British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
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Hydrology Research (2014) 45 (6): 755–773.
Article history
Received:
November 05 2012
Accepted:
December 05 2013
Citation
A. M. MacDonald, D. J. Lapworth, A. G. Hughes, C. A. Auton, L. Maurice, A. Finlayson, D. C. Gooddy; Groundwater, flooding and hydrological functioning in the Findhorn floodplain, Scotland. Hydrology Research 1 December 2014; 45 (6): 755–773. doi: https://doi.org/10.2166/nh.2014.185
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