Geoscience Reference
In-Depth Information
of current condition requires an audit of the
amount, distribution and location of specific
habitat types within catchments. Ideally, these
hydromorphological audits should aim to identify
influences on both reach and catchment-scale
ecological processes and to consider whole
river-system response and resilience in the
face of future climate change (Ormerod and
Durance, this volume). However, assessing
systemic hydromorphology is at present limited
to broad-scale approaches; few methods have
been developed and tested to operate at a range
of spatial scales and which have predictive ability
and the capacity to use expert opinion. In the UK,
MImAS (Morphological Impact Assessment System
- SNIFFER, 2006), River Habitat Survey (Raven
et al
. 1998a,b), biotype assessement (Newson and
Newson, 2000) and Geo-RHS (Geomorphological
RHS - Branson
et al
., 2005) are the only datasets
currently available for consistent assessment within
and between catchments (Table 31.2).
The WFD approach used to classify rivers
for river basin plans uses gradient, altitude
and geology criteria based on a number of
assumptions: (i) the river type contains a certain
morphological assemblage; (ii) potential impacts
are assessed using expert opinion to derive
a modification score - principally for channel
morphology as a result of direct physical alteration;
and (iii) modification determines ecological status.
Improving the current state of knowledge depends
on a better understanding of the ecological
response to engineering modification and habitat
rehabilitation work. For example, in regulated river
systems there are major effects from dams on
the flow regime, longitudinal continuity and the
downstream channel morphology. Although rapid
and simple post-project evaluation of engineered
river restoration schemes can be carried out and
presented in a way that is easy to understand by
the public ( Aberg and Tapsell, this volume), they
are likely to be too 'static' to inform longer-term
river management strategies. Consequently, a more
dynamic understanding of hydromorphology needs
to be embraced both by the scientific community
and the general public, which takes account of river
processes as much as physical form.
However, there are major challenges in this;
for example, media coverage of recent flooding
in the UK has highlighted local opposition for
allowing rivers to alter their course and be
given sufficient floodplain space to function in a
more natural fashion. Inter-disciplinary knowledge
remains inadequate, particularly in regulated
systems with impacts on channel morphology in
natural flow regimes; consequently, there is a
disproportionate dependency on expert opinion,
often from a limited number of individuals, for
river management advice at catchment, reach
and habitat scales. The WFD puts new demands
on river science, not least to apply 'useable
knowledge' and develop practical 'tools' that allow
informed decision-making at a variety of scales
(Newson, 2002; Sear and Arnell, 2006). Ecological
science cannot, in isolation, provide the predictive
capability required, particularly in relation to WFD
reference conditions (Newson, 2002). The need
to develop more predictive and process-based
assessment and monitoring tools for rivers in the
UK would therefore allow hydromorphology to be
viewed not simply as a component for complying
with the WFD, but as a genuine and integral part
of condition assessment and river management
decisions.
Floods - living with uncertainty
During 2000-2010, northern England was affected
by several damaging floods, notably affecting York
(2000), Carlisle (2005), Morpeth (2008), and
Cockermouth (2009). Damage to property and
livelihoods was severe. It is currently not possible
to conclude whether these extreme events are
part of a pattern of wider hydro-climatic change.
However, the UKCIP02 programme scenarios (UK
Climate Impacts Projections 2002 programme,
now superseded by the UK Climate Projections
2009 - UKCP09) indicate that, by the 2080s,
increases in winter precipitation of up to 30%
and summer decreases in precipitation up to 80%
could occur in the UK (Hulme
et al
., 2002; Fowler
et al.
, 2007). A more important implication is
the prediction of an increase in the magnitude
