Título:

The environmental impact and risks associated with changes in fluvial morphodynamic processes

Resumo:

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 enables a specific longitudinal profile to develop which is dynamic and constantly in search of an equilibrium between the rates of liquid discharge, erosion and the transport and deposit of sediment. 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.

Autores:

José Simão Antunes do Carmo