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| Cause: Drainage system obstruction, Uige. |
The Earth we know today was not always so. Over millions of years have undergone
significant changes brought about by numerous geological phenomena aimed at your balance, some internal order, creating new geological
formations and other external
order smoothing formations
previously created. From the tectonic standpoint, Angola
is located in a relatively stable
area which gives it a certain privilege when
compared with some Asian countries or even Americans
where quite often occur earthquakes and
volcanic eruptions.
However, at the same it cannot be said in relation to the occurrence of external
geodynamics phenomena, such as the ravines, which in recent
years has taken shape in many provinces, especially due to anthropogenic activity, giving rise to geological
hazards. In addition, increasing the risk of damage in buildings and
others infrastructures, losses direct or indirect in economic activities and
loss of human lives. We understand that the
reducing of these risks starts,
in particular, by their identification, for later take preventive
measures.
This work is the result of some research work carried out by the author through erosion courses of soil and stabilization
of soils subject
to erosion phenomena, carried
out by Engineering Laboratory of Angola (LEA).
For the realization of this work, we resorted to cartographic data query, literature, listening to some of the provincial representatives
and local residents, as well as the observation in loco of some affected areas.
The results allow us to infer that the main provinces affected by ravine phenomenon are located in Central and Northern highlands, as well as in the eastern region, and more recently in Cuando-Cubango province. Not ruling out, however, other regions, such as in Luanda and Cabinda [1].
Relatively
the causes, we can say that the ravines in Angola are primarily due to the
combination of three natural factors: climate, topography and type of soil [2]. When we add the anthropogenic activity, namely
the execution of construction works, the drainage system obstruction, exploration
of minerals, agriculture and fires, it is verified an increasing of the phenomenon,
often requiring immediate action. These interventions can be done through structural or engineering measures and by the stabilization measures on the degraded soil cover [3]. We present an example of stabilization measures through the deployment of a local vegetation called Pennisetum purpureum.
It is expecting that the results may
contribute to a better understanding of the causes of the ravine phenomenon in
Angola and that the adopted stabilization method can be adapted in other
affected provinces in order to prevent and making the contention of the
ravines.
 |
| Stabilization measure: vegetation deployment |
 |
| Stabilization measure: estrutural measure |
[1] Governo de
Angola. (2011) In: Plano Estratégico de
Gestão de risco de desastres. Diário da República. I Serie Nº95, 2962-2963
[2] Chinguar L
(2011) Erosão, um fenómeno natural e
previsível, mas que surpreende sempre
[3] LEA and LNEC
(2014) Curso de Erosão dos solos
