A rising exposure to flood risk is a predicted consequence of increased
development in vulnerable areas and an increase in the frequency of
extreme weather events due to climate change. In the face of this
challenge, a continued reliance on engineered at-a-point flood defences
is seen as both unrealistic and undesirable. The contribution of soft
engineering' solutions (e.g. riparian forests, wood in rivers) to
integrated, catchment scale flood risk management has been demonstrated
at small scales but not larger ones. In this study we use reduced
complexity hydrological modelling to analyse the effects of land use and
channel changes resulting from river restoration upon flood flows at the
catchment scale. Results show short sections of river-floodplain
restoration using engineered logjams, typical of many current
restoration schemes, have highly variable impacts on catchment-scale
flood peak magnitude and so need to be used with caution as a flood
management solution. Forested floodplains have a more general impact
upon flood hydrology, with areas in the middle and upper catchment
tending to show reductions in peak magnitude at the catchment outflow.
The most promising restoration scenarios for flood risk management are
for riparian forest restoration at the sub-catchment scale, representing
20-40% of the total catchment area, where reductions in peak magnitude
of up to 19% are observed through de-synchronization of the timings of
sub-catchment flood waves. Sub-catchment floodplain forest restoration
over 10-15% of total catchment area can lead to reductions in peak
magnitude of 6% at 25years post-restoration. Copyright (c) 2016 John
Wiley & Sons, Ltd.