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Sustainable systems for soil stabilization

Prof. Roberto Valentino

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Kigali-Musanze NR

Landslides in Rwanda…

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Is it possible to adopt sustainable systems for soil stabilization?

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Normally, sustainable systems are under the name of «bioengineering»

Bioengineering deals with engineering purposes, and can be applied with lower costs than common retaining engineering structures.

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What bioengineering is?

Bioengineering deals with a sustainable technique for landslides risk management and prevention. It can be used before and after the landslide occurrence and also for different situations.

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What bioengineering is?

Philosophically, it represents the linkage between human rationality and nature.

Bioengineering also provides a safer environment for people and enhances biodiversity if applications are well built.

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How soil bioengineering is applied?

Usage of living plants as material. They may be herbs or shrubs with good adaptation characteristics;
At first, small piles, cages or soil are adopted to help the first rooting period: the perspective is to initiate a natural colonization process which will continue alone;
The main and most important characteristic is that all the applications should be totally adaptable to the environment: only biodegradable materials and local plants are used, by taking into account soil and litology.

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Pits, slopes, embankments

Rivers

Soil structural bioengineering

Dead material (wooden trunks)

Living plants

Auxiliary material (especially for erosion prevention)

Is applied to…

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Is it applied anywhere?

Unfortunately, no. At least, not in the sustainable way.
There are many situations where the hazard is too high and it is impossible to wait for plants to restore the natural environment.

e.g: In Europe, for example, and especially in Italy, it happened many times that big areas were placed with non-native ecosystems…Thus, is it still sustainable or not?!

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An example: Apennines area (central Italy)

Natural: mixed oak forest, hard wood (Quercus spp, Fraxinus, Epipactis, Achillea, Castanea etc etc…)

Reforestation: pinewood (Pinus Nigra)

A tree that does not belong to any natural and pure forest in Italy!!!

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Which kind of plants are to be used then?

A mix of species that belong to the same native phytosociological association
Plants with different complementary roots systems
Pioneer plants = those which are naturally able to colonize and create new habitats

(e.g.: Leguminosae are a family of plants that can fix N₂ from the atmosphere fertility arises natural evolution of the ecosystem)

Hardy plants = those which do not need fertile soil

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Different kinds of structures: streambanks

Auxiliary biodegradable material: we need them to avoid hydrodinamic base scour (also rocks are normally used for this purpose)

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