Water in Celtic Countries: Quantity, Quality and Climate Variability
(Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management
of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 307-319.
The environmental impact and risks associated with
changes in fluvial morphodynamic processes
JOSÉ SIMÃO ANTUNES DO CARMO
IMAR – University of Coimbra, Department of Civil Engineering, Pólo II of the University, 3030-788 Coimbra, Portugal
Abstract The dynamics of the inter-relationship between the various elements
that constitute a hydrographic basin involve cause–effect relationships that
can lead to constant alterations in fluvial dynamics. The combination of
elements such as morphology, altimetry and structural controls in a fluvial
network enable a specific longitudinal profile to develop, which is dynamic and
constantly in search of an equilibrium between the rates of water discharge,
erosion and transport. Human activities carried out on a stretch of a river may
alter this balance in different ways and with differing levels of intensity.
Whenever the characteristics and natural evolution of a river are altered as a
result of human intervention, this has an environmental impact. In other words,
it is understood that differences can be observed between any present situation
that is the result of the evolution of an environment after human intervention,
and the natural situation that would have existed if this type of intervention
had not taken place, taking into account our previous knowledge of the
situation. This paper provides a description of the nature and distribution of
the direct and indirect types of impact arising out of the building and
operating of large dams, as well as some specific points that should be taken
into consideration. It also reflects on the way in which the problem of extracting
inert material from water environments has been dealt with in Portugal and
offers a brief technical contribution which, although qualitative, provides a
basic record and explanation of the consequences of significant interventions
in water environments that have not been properly assessed or have not taken
other mitigating circumstances into consideration.
Key
words dams;
environmental impact; extraction of inert material; morphodynamic processes;
risks