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| Titel |
Removal of river embankments and the modelled effects on river-floodplain hydrodynamics |
| VerfasserIn |
Hannah Clilverd, Julian Thompson, Kate Heppell, Carl Sayer, Jan Axmacher |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112796
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| Publikation (Nr.) |
 EGU/EGU2015-12974.pdf |
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| Zusammenfassung |
| The channelization and embankment of rivers has led to major ecological degradation of
aquatic habitats worldwide. River restoration, which often includes the removal of previously
constructed barriers between a river and its floodplain, is now being widely used to create
favourable hydrological conditions for target species or processes. However the effects of
river restoration on hydraulic and hydrological processes are complex, and are often difficult
to determine due to the infrequency of long-term monitoring programmes before and after
restoration works. To examine the hydrological impacts of embankment removal under a
variety of possible hydrological conditions, we developed coupled hydrological/hydraulic
models of pre-embankment and post-embankment conditions at a wet grassland meadow in
Norfolk, UK using the MIKE-SHE/MIKE 11 system. Groundwater hydrology and climate
were monitored between 2007 and 2010 with river inflows being provided from an upstream
gauging station. The embanked model was calibrated and validated with observed
groundwater data for two consecutive 12-month periods, after which the restored topography
was applied to the model and validated for a subsequent 12-month period. The
restored model was then run for the same period as the embanked model (i.e. with the
same river inflow, precipitation, and potential evapotranspiration data) to remove
interannual climate variability and enable a direct comparison between models.
Modelled groundwater levels compared well with piezometer observations and
reproduced the observed rapid groundwater response to high magnitude rainfall
and river flow events. Removal of the embankments resulted in frequent localised
flooding at the river edge, widespread floodplain inundation at flows greater than 1.9
m3 sec-1, as well as higher groundwater levels and greater subsurface storage.
Restoration had only a minor effect on flood peak attenuation (maximum 5% flood peak
reduction), likely due to the small size of the restored river reach (~400 m), and
improved free drainage back to the river. Our results suggest that embankment
removal can increase river–floodplain hydrological connectivity to form a more
natural wetland ecotone driven by frequent flood disturbance. This has important
implications for the planning and management of river restoration projects which aim to
enhance floodwater storage, river water quality and floodplain species composition. |
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