In my
previous post, I summarized some of the introductory presentations at CICES,
the IECA Iberoamerican Chapter’s October 2012 conference in Granada,
Spain. In this post, I’ll focus on a few
of the subsequent presentations that dealt with erosion and sedimentation
issues in Spain and Latin America. These
were not necessarily the “best” presentations (although they were good to
excellent) but I wanted to include examples from several different countries in
order to give you readers a better idea of the wide geographical range of
professionals working on erosion and sedimentation issues in Spanish and
Portuguese speaking countries. At least
17 countries were represented at the conference.
Olive
groves are found in great abundance in the Andalucía region of southern Spain. We had several presentations about erosion
problems associated with olive cultivation.
One was titled “Initiative
against erosion through integrated restoration in watersheds dominated by
steeply-sloping olive groves in Andalucía” (my English translation). The authors included some spectacular photos
of catastrophic erosion in olive groves.
The principal author, Federico Julián Fuentes, noted that this problem
has accelerated since the mechanization of Spanish agriculture took off in the
1960s. He pointed out that social,
economic, legal, administrative, and technical factors are obstacles in the
restoration of affected watersheds. He
spoke of the need for a pilot project which would include not only technical
studies but also incorporate an action plan supported by the participation,
collaboration, and consensus of public administrators, affected farmers,
environmentalists, and civic organizations.
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Left: Small rivulets start to develop between lines of olive trees planted on a slope. Right: The rivulets naturally evolve into large gullies with time.
photos from presentation by Federico Julián Fuentes
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There
were a number of presentations from Argentina.
“Riparian infrastructure for urban restoration in the city of Tartagal,
Province of Salta, Argentina” (presented by Gustavo Arce) focused on traditional
structural measures to control slope failures adjacent to a deeply incised
river channel in a densely populated urban area. Throughout its history, the Tartagal River
has suffered from floods which undercut steep hillsides causing homes to
collapse. To address this problem,
engineers from INMAC, a Buenos Aires-based consulting firm specializing in erosion
and sediment control, used geotechnical approaches such as retaining walls
(gabions and reinforced concrete) to channelize the river. My first impression was that their approach
was perhaps a bit heavy on large-scale structural controls. However, in a crowded urban setting, I wonder
if this is perhaps a more practical option than an environmentally-friendly and
aesthetically-pleasing design relying on bioengineering.
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Photos at the beginning of construction (top left) and following completion (bottom right) show how the steep unstable slope on the top left was moderated and terraced above the new retaining walls.
photos from presentation by Gustavo Arce
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Gino
Mathews from Peru gave a presentation on erosion control training for rural
communities in the Peruvian highlands. The training aims to take the skills of
indigenous people who have a long history of working with earth and rock to
construct agricultural terraces and apply these skills to the mining
industry. People from local communities
can then become employed in erosion and sediment control for the mining
companies from the exploration phase all the way through mine
post-closure. In the process,
cooperation between the mining companies and local communities is fostered,
indigenous people get good-paying jobs without migrating to cities, and the
mining companies can legitimately claim that they are helping local communities
and using the skills of local people to protect the environment. Seems to me like the type of project IECA’s
SOIL Fund should get involved with. IECA
can provide skilled erosion control professionals like Gino Mathews to provide
the training and the mining companies can provide funding.
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Photo from presentation by Gino Mathews illustrating the terrific skill of indigenous Andean people in construction of agricultural terraces on precipitous slopes.
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Paula
Pereira talked about the use of bioengineering for stream bank restoration. She co-authored a paper (“Protection and
Recuperation of Stream Course Margins Using Bioengineering”) describing methodologies
used and monitored in the states of Bahia and Minas Gerais, Brazil. Sediment retainers, wooden fences, and berms
packed with live cuttings resulted in satisfactory stream bank protection. These low cost BMPs were easy to install and
environmentally compatible. Senhorita (that’s
Portuguese for señorita) Pereira is employed by DEFLOR Bioengenharia based in
Belo Horizonte, Brazil. Another DEFLOR
employee, Luiz Lucena, spoke on erosion mitigation using bioengineering along
the Atlantic coast of Brazil.
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Examples from Paula Pereira’s presentation showing stream bank stabilization using live cuttings planted along layers of soil which have been covered with natural fabric blankets.
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Ricardo
Schmalbach spoke about various erosion control techniques used on the Rio
Magdalena, the principal river in Colombia which drains northerly to the
Caribbean. Record floods along the
Magdalena during the winter of 2010-2011destroyed large areas of agricultural
and industrial facilities, ports, and roads.
More than 500,000 people were displaced and 100,000 are still
homeless. Dr. Schmalbach described the
use of “megabolsas” (huge sandbags weighing several tons each) to repair a
critical broken jetty along the Magdalena.
Geotextile bags with a capacity of 13.5 cubic meters are filled with
sand, dropped into the water from dump trucks, and positioned with excavators
(track hoes) to build dikes.
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Construction of a flood control dike along the Rio Magdalena in Colombia using “megabolsas.” The huge bags are compacted and consolidated by both their own weight and by the passage of trucks across them as more megabolsas are added.
photo from presentation by Ricardo Schmalbach
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We tend
to think of El Salvador as a poor, backward Central American nation. Thus, it was encouraging to learn that
state-of-the-art erosion control techniques employing heavy equipment were used
in construction of a new 290km highway in the northern part of the country
(“Slope Protection on the Northern Highway, El Salvador” by Oscar Alfredo Rivas
Cerna). To protect cut and fill slopes
from failure in the tropical climate, geomat incorporating a double-twist
hexagonal mesh attached to a filament-reinforced polypropylene was
installed. It was secured with rod
anchors placed in a mortar slurry on a 2-meter-spaced grid across the
slope. 30,000 square meters of this mesh
were used on slopes which had a high probability of failure. On another 12,000 square meters of slopes
with relatively lower stability hazards, natural fibrous geomat (such as coir)
was used to promote natural revegetation.
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Using a hydraulic elevator for emplacement of hexagonal mesh and erosion control blankets and for drilling holes for rod anchors, Northern Highway, El Salvador.
photos from presentation by Oscar Alfredo Rivas Cerna.
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You may
have seen my earlier postings from Bali and Thailand discussing the use of
vetiver grass for erosion control. Oscar
Rodríguez Parisca of the Central University of Venezuela pointed out that climate
change will bring ecological, economic and social impacts to vulnerable populations
in developing countries (“Adaptation to climate change through the use of
vetiver systems: A tool for soil
conservation and community development”).
He pointed out that use of vetiver is a simple, low cost option for soil
stabilization that is tolerant of environmental extremes and is, therefore,
suitable for communities adapting to climate change. Examples were presented showing applications
of vetiver systems to various types of impacts.
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Examples of use of vetiver for erosion control in Venezuela: coffee plantation (upper right) & bauxite mine reclamation (lower left).
photos from presentation by OscarRodríguez Parisca.
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Julie
Etra (IECA’s VP for International Development) and I were the only “gringos”
who spoke at the conference. Julie
talked about the challenges of identifying appropriate best management
practices for erosion control and revegetation in arid areas. For example, revegetation of disturbed sites
will often fail unless it is combined with rainwater harvesting to provide
adequate moisture for germination and initial growth of native vegetation.
When wattles are installed in low
rainfall environments, they are of little use if vegetation plantings have
insufficient moisture for survival.
photo by Pablo A. Garcia-Chevesich from presentation by Julie Etra.
Julie
had an easier time presenting in Spanish than I did as she had the good fortune
of attending a private high school in Spain and now lives part of the year in southern
Mexico. Luckily for me, Julie and
Gustavo Salerno (IECA Region I board member from Argentina) translated the
English presentation of my erosion survey in Ecuador (including PowerPoint
slide captions) into excellent Spanish.
All I had to do was practice it a few times before the conference, and
Julie was there for my presentation to help me with questions from the
audience.
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Muchas gracias to Gustavo Salerno and Julie Etra for their translation of my presentation into Spanish!
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