Geoscience Reference
In-Depth Information
Theroleoffluvial
geomorphology in river
conservation
biotype approach (Newson and Newson, 2000)
and GeoRHS method (Branson
et al.
, 2005)
offer potential ways forward, but capturing
geomorphological and biological data depend at
present on intensive surveys and fieldwork - and
these are unlikely to be funded at sufficiently
extensive geographical scales to meet WFD needs
such as an accurate assessment of ecological status.
While there are exceptions (Darby and Sear,
2008), much of the data gathered that links
biota to habitat (and by inference to process)
has been static in nature, constrained by the
traditional focus of benthic macroinvertebrate
sampling methods for specific instream habitat
types (Figure 31.3). In addition, spatial and
temporal deficiencies in sampling can lead to
distortions such as data aliasing or smoothing,
sometimes suggesting trends that do not reflect the
true picture (Bl oschl, 1996). These problems imply
the need for better specification of data capture
and confidence in interpretation by end-users
to the scientific community. This user-specified
research should not be the exclusive approach
because it would undermine the strong justification
for 'pure' river research and the advances made
through other means. These include long-term
research (Macklin and Lewin, 1997; Sear and
Arnell, 2006; Beechie
et al
., 2010), and strategic
research programmes involving end-users such as
the Flood Risk Management Consortium (FRMRC)
in the UK.
Relatively little attention has been paid to
natural hydrological variability in river systems,
although it plays an important role in defining
hydromorphological character. Managing fluvial
systems is difficult without a better scientific
understanding of variability, so quantifying this
variation is essential. Fluvial geomorphology has
an obvious role in this respect - it is now in a
much stronger position than before because of
a broadening research base and its contribution
to complex inter-disciplinary problems is now
more widely recognized (Dollar, 2004). This
is important because previously many policy
decisions relating to river management have been
made without adequate consideration of the
spatial and temporal complexity of fluvial systems
It is widely acknowledged among river scientists,
end-users and practitioners that problems
remain regarding: (i) the definition of reference
('natural' or undisturbed) hydromorphological
conditions for rivers; (ii) the assessment of
departures from a reference state; and (iii)
agreement on the ecologically driven strategies for
river restoration (Newson and Large, 2006).
There are also significant economic costs
involved in implementing successfully the
requirements of the WFD. Major problems
include sub-optimal monitoring strategies, a
presumption about 'active' engineering-based
restoration (which is very costly) and the lack of
tangible evidence linking restoration/rehabilitation
with tangible ecological and economic benefits
beyond the immediate project location ( Aberg and
Tapsell, this volume).
A scientifically based and economically
sustainable way of managing rivers and floodplains
requires a clear definition and consistent
application of the term 'hydromorphology' and
its associated requirements for quantitative and
qualitative scientific information. This is not easy.
Foralongtimeaftertheterm'geomorphology'
was first used in the 1880s (Goudie, 1985),
the discipline was considered by many other
scientists as somewhat 'unscientific' and lacking
true predictive capability (Tooth, 2009). Similarly,
'hydromorphology' has also suffered from this
view because several facets of river science remain
weak or qualitative. For example, Vaughan and
Ormerod (2010) point out that many biological
and geomorphological datasets have little or no
temporal dimension (although flow gauging is
an exception), and that significant scientific and
river management issues arise when data collected
originally for different purposes are interpreted for
conservation purposes. Truly integrated ecological
approaches are not yet available, so there remains
a pressing need for data to be collected over
the full range of flows to describe habitats and
their
functioning
adequately
(Poff,
2009).
The
