MAKING SPACE FOR WATER CONFERENCE
Restoration of blanket bogs; flood risk reduction and other benefits
23 April 2015, University of Manchester, Renold Building
Tim Allott, Emma Shuttleworth, Martin Evans
University of Manchester
Restoration and storm-flow in peatland headwaters
Restoration of peatland headwater catchments has the potential to reduce downstream flood
risk through changes in catchment storage and/or storm runoff behaviour. To date, however,
there has been little research on stream flow responses to the most common restoration
practices of re-vegetation of bare peat and gully blocking. We report here on an intensive field
monitoring campaign over five-years (2010-14) in the form of a before-after-control-impact
study of degraded micro-catchments on Kinder Scout with additional data from established
reference sites. The monitoring focused on evaluating changes in storm flow behaviour
following restoration and assessment of water table conditions and overland flow generation at
various stages of the erosion-restoration continuum.
Restoration has resulted in statistically significant changes in all but one of the hydrological
parameters studied. Catchments became wetter following re-vegetation – water tables rose by
35 mm and overland flow production increased. Storm flow lag times in restored catchments
increased by up to 267%, while peak storm discharge and hydrograph shape index decreased by
37% and 38% respectively. There were no statistically significant changes in percentage runoff,
indicating limited changes to within-storm catchment storage. Although there appear to be some
additional benefits of gully blocking, these are not statistically significant when compared to the
impacts of re-vegetation of bare peat alone. The results show that storm water moves through
restored catchments more slowly, attenuating flow and storm hydrograph responses. The key
hydrological process response to restoration is a reduction in flow velocities associated with
increased surface roughness following the establishment of vegetation cover.
We conclude that restoration significantly alters peatland storm runoff behaviour, delaying the
release of storm flow from headwater catchments with benefits for downstream flood reduction.
The study provides robust empirical data and process analyses to inform and calibrate
hydrological models and to quantify the flood risk benefits of restoration at larger catchment
scales.