Geoscience Reference
In-Depth Information
Hydromorphology: a new
terminology for river
conservation
length of watercourse created by human activity
(e.g. a canal); (ii) 'heavily modified water body'
(HMWB) is a length of river that has been changed
substantially from its natural physical state through
modifications such as channel straightening or
bank reinforcement and which is maintained in
this condition primarily for socio-economic reasons
- notably agricultural production, industrial use
and urban development. The HMWB category
clearly has implications for the integration of
hydromorphology into river restoration practice.
This is because the requirement for HMWBs to
achieve good ecological potential implies having
the necessary means for measuring improvements
of management actions.
There is a new international impetus for achieving
a more integrated approach to river management
and conservation. The WFD (Council of the
European Communities, 2000) is the most
far-reaching and important legislation for water
management in Europe to date (Newson and Large,
2006). Together with the EC Habitats Directive
(HD, 92/43/EEC; Council of the European
Communities), it requires rivers to be managed
in a way that maintains and improves ecological
quality and ecosystem health, determined partly
on the basis of 'hydromorphology'. The WFD
presents major challenges for the management
of inland fresh water and coastal waters because
Member States must aim to achieve 'good
ecological status' (or 'good ecological potential'
for 'heavily-modified water bodies') by December
2015. The term 'hydromorphology' was introduced
in WFD documentation to describe the physical
character and quality of water bodies; this was
to complement more traditional chemical and
biological quality elements. The term has recently
become prominent because of the need to consider
the variety of natural and anthropogenic variants of
river flow regime as well as fluvial geomorphology
(i.e. processes and landforms) in the description
of rivers (Newson and Large, 2006). As the WFD
has three 6-year cycles of river basin management
plans up to 2027, it will have a profound effect on
land and water resource management in Europe
over the next 20 years.
The four most important principles of the WFD
are: (1) to manage water on the basis of river
basins; (2) to use a combined approach for the
control of pollution, setting both emission limits
and water quality objectives; (3) to reflect the
true cost of water and ensure that users bear
the cost of provision and use; and (4) to involve
the public in decision-making (Council of the
European Communities, 2000; Logan and Furse,
2002; Large
et al
., 2005). Two technical definitions
(Article 2, WFD) are important in the context of
water status: (i) 'artificial water body' represents a
The need for predictive
approaches
For the WFD, hydromorphological attributes are
a primary factor determining the high ecological
status classification of water bodies; elsewhere they
are used in support of biological quality elements
for classifying good and moderate ecological status.
To establish baseline conditions an extensive
network of monitoring is required, using methods
that variously describe river hydrology, hydraulics,
geomorphology and ecology and together take
account of the complex interactions between
them (Figure 31.2). However, a review of
existing approaches to hydrological, biological and
geomorphological typologies in rivers confirms that
few such integrated classifications exist (Table
31.2); in addition, none of the existing typologies or
methods can simply be applied to rivers outside the
geographical areas for which they were developed
(Large
et al
., 2005; Orr
et al
., 2008). This presents
a problem when trying to establish a common
classification and assessment framework for WFD
and other purposes (Boon
et al.
, 2010).
Typologies are designed to incorporate current
knowledge of driving process variables while
classifications are empirically based (Naiman
et al
., 1996). There is a need to improve process
information, or at least surrogates for process,
if, for example, potential climate change effects
