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cumulative time-lag effect, particularly in relation
to flood risk and hazard management.
et al
., 2009). However, a key catchment-scale
research challenge over the next 20 years will be to
better understand hydromorphological complexity
and the linkages with biological communities
to establish which river attributes need to be
measured and what information can and cannot
be simplified. Improved communication between
hydrology, fluvial geomorphology and ecological
sciences will be vital to encourage the development
of more reliable typologies, predictive modelling,
and monitoring procedures that are needed to
support adaptive management (Hamill and Melis,
this volume). An increased role for modelling
is needed for a better understanding of habitat
variability over varying hydrological regimes and
also simulating hydromorphological changes over
time. Some modelling approaches are beginning to
integrate directly the role of plants, woody debris,
invertebrates and other 'ecosystem engineers' in
hydromorphological alteration. This work should
be encouraged, and its scope broadened to
incorporate palaeo-hydrological modelling for a
better understanding of natural variability across
the timescales that climate change is likely to
influence (Sear and Arnell, 2006; Seddon
et al
., this
volume).
Climate change implies that present conditions
will not remain static and it also raises the
possibility that reaches used for reference purposes
may no longer provide reliable templates for river
conservation and management. Reduced resistance
and resilience - both at the reach and micro-habitat
scale - are predicted to be a consequence of climate
change, so sustainable river conservation will need
to build on innovative legislation drivers such as
the 1998 Republic of South Africa Water Act. This
Act recognizes that water is a 'scarce and unevenly
distributed national resource which occurs in many
different forms which are all part of a unitary, inter-
dependent cycle'; that it forms a natural resource
that belongs to all people; and that the ultimate
aim of water resource management is to achieve
the sustainable use of water for the benefit of all
users. In the face of increasing water stress world-
wide, river conservation needs to be recognized as
a
bona fide
water use; paying for access to water
invokes rights to specific quantities (and quality)
Challenges for the future
In setting out their '2020 vision', Rice
et al
. (2010)
emphasized that fluvial geomorphology needs to
sit alongside stream hydrology and hydraulic
engineering as a key element of an integrated,
inter-disciplinary scientific approach. To achieve
this, several areas of improvement by the scientific
community need to be made. Messages need
to be simplified - river science is currently full
of jargon which hinders understanding by local
communities and the general public. There is also
a need for better education, such as explaining
the benefits of river channels that are free to
adjust. The concept of 'making space for a river'
needs to be supported by evidence that allowing
a river to move will protect riparian interests.
By encouraging wider society to embrace greater
uncertainty but with the promise of longer-term
benefits, the challenge of what a 'natural' river
really is remains. As Newson and Large (2006)
emphasize, in the UK they are not 'wilderness
channels', but watercourses that need some
management intervention to encourage a diversity
of physical habitat and increase resistance and
resilience to climate change. The inherent value
of these rivers and streams increases with their
occurrence as a proportion of the drainage network
- but then so too does the uncertainty as to how
the river might behave. The case for retaining
the 'organic sediment' load of rivers is similar
(Gurnell
et al
., 2002); so is the removal, where
feasible, of culverts and weirs to improve capacity
of rivers for future 'assisted natural recovery'.
Self-evidently, this general approach requires the
support of interest groups and individuals affected
by the changes in river management (Williams,
2006).
Anticipated funding reductions might strengthen
the case that current research priorities should be
to 'use existing literature or data better to identify
patterns among organisms, ecological functions
and river hydromorphological character' (Vaughan
