1.0
Setting
This erosion assessment took place in an area encompassed by the Malingua Pamba Water Project
(Figure 1-1) which has been the focus of activities of the Denver Professional Chapter of Engineers
Without Borders (EWB-Denver) since November 2006. The water project has included an assessment of
the water supply and an improvement of potable and irrigation water supplies for communities of
Malingua Pamba and Tunguiche in northwestern Ecuador (Figure 1-2). These two communities are
separate political entities but are located in the same watershed and share a common water right to
surface waters and springs within the watershed. For the purposes of this report, the two communities
will be referred to collectively as the Malingua Pamba community.
1.1
Geography
Malingua Pamba is a rural mountain community in the Western Cordillera of the Andes. It is situated
about 115km south-southwest of Quito (Ecuador’s capital) and 30km west-northwest of Latacunga (the
provincial capital). Malingua Pamba is located in the parroquia of Isinliví, cantón of Sigchos, and
province of Cotopaxi. Approximately 720 people currently live in the community. It includes two
central areas containing schools, churches, and small concentrations of buildings and a larger
geographical area (approximately six square kilometers) composed of sectors where most families of the
community live and farm. Sectors of Malingua Pamba include Malingua (the central area), Chilcaucu
and Pucará. Sectors of Tunguiche include Tunguiche (the central area), Quadrapamba, Pinalí,
Cachiloma,Yana Yacu, Chimbusí and Tingo.
Figure 1-1. View of Malingua Pamba community and surrounding area from across canyon of Rio Toachi. View of
Tunguiche (bottom center, area with blue roofing), Malingua Pamba community center (upper third, center), Pucará
(upper third, right), and Timgo (lower right). Most other sectors located to the left of photo. Photo by
Figure 1-2. Malingua Pamba is located in Cotopaxi Province of northwestern Ecuador. reference?
From the drainage divide east of the community, the land surface slopes sharply to the west to the Rio
Toachi (called Rio Mestizo on some maps) which forms the western boundary of the community.
Elevations range from 2900m (~9500ft) along the river at the northwest corner of the community to
over 4100m (~13,450ft) along the drainage divide which forms the de-facto eastern community
boundary. Thus, relief within this small community is approximately 1200m (nearly 4000ft). The
generally westward-sloping land surface is sharply dissected by steep gullies (“quebrada” in Spanish –
abbreviated “Q.” in this report).
1.2
Geology
The Andes were formed by the collision of the westward moving the South American plate with the
Pacific plates. The resulting upthrust of continental rock began in the Miocene Era, about 25 million
years ago. This process was accompanied by intense volcanic activity uplifting the Andes to greater
heights, a process which has continued to the present (Neill. 1999a).
Bedrock of the Pisayambo formation (late Miocene and Pliocene age) (MRNE et al., 1982) outcrops at
the surface in the Malingua Pamba area (Figure 1-3). Its origin is explosive volcanic eruptions and it
consists mostly of pyroclastic rock such as welded tuff and andesite (formed from andesitic lavas).
Figure 1-3. Outcrops of pyroclastic bedrock and unconsolidated volcanic materials above
Q. Yaranumi. Elevations at this location range from approximately 3700 to 3900m.
Throughout the Andes of northern and central Ecuador, deposition of thick layers of ash from volcanic
eruptions during the present Quaternary Era have continued (Neill, 1999a). However, the contemporary
landscape in the Malinua Pamba area reflects the dominance in recent millennia of erosive processes
(mostly surface water flow and gravity) rather than the occasional deposition of ash and other materials
from volcanic eruptions.
Geologic instability in the region continues to the present as evidenced by periodic earthquakes some of
which have been very destructive to Ecuadorian communities. For example, an August 1949
magnitude 6.8 earthquake centered near the city of Ambato (60km southeast of Malingua Pamba)
resulted in more than 5000 fatalities (USGS, 2011). A March 1996 magnitude 5.7 event was centered
southwest of Latacunga and only about 40km southeast of Malingua Pamba (EERI, 1996). This
earthquake totally or partially destroyed up to 85 percent of the housing in Pujili and had major impacts
in Zumbahua, less than 20km south of Malingua Pamba. North-south and east-west trending faults
within a few kilometers of Malingua Pamba provide evidence of the community’s vulnerability to seismic
events (MRNE et al., 1982).
1.3
Climate
The Malingua Pamba area has a humid tropical highland climate characterized by low seasonal variation
in temperatures with daily fluctuations which are more pronounced (Neill & Jørgensen, 1999). The
climate at lower elevations (2900-3500m) is relatively temperate with nighttime temperatures rarely
dipping below 0oC. Above 3500m, the climate is cooler limiting farmers to only a few cold-tolerant crops
such as potatoes and fava beans. Depending on altitude, average temperatures range from 10 to 18oC
(MAGE, 1983).
The major dry season occurs from June through August with a less pronounced dry period in January
(Neill & Jørgensen, 1999). The high rainfall period occurs in March and April while there is another less
rainy period in October. During the rainy season, precipitation frequently occurs as afternoon
thunderstorms with occasional hail. Snowfall is rare below 4000m. Annual precipitation in the Malingua
Pamba area is 1200 – 1500mm.
1.4
Hydrology and Water Quality
The community lies entirely within the Rio Toachi watershed, a sub-basin of the Rio Esmeraldas which
drains north-northwest to the Pacific Ocean in northwestern Ecuador.
Surface drainage in the community is westerly to the Rio Toachi and has a sub-parallel pattern
characteristic of steep, highly erodible volcanic terrain. Both the larger perennial and smaller
intermittent drainage channels tend to be moderately to deeply incised into the deep sandy volcanic
soils and soft volcanic bedrock. Waterfalls and dryfalls are found where channels encounter more
consolidated layers of bedrock (Figure 1-4).
Figure 1-4. Waterfall east of Pucara where
Q. Yaranumi flows over a resistant layer of
welded volcanic tuff.
.
Although no stream gauging stations occur in the area, informal observations indicate wide fluctuations
in flows with both small perennial and intermittent streams sometimes becoming raging torrents during
rainy season storms. It is during these events that a majority of erosion and sedimentation appears to
occur. Field reconnaissance during the July dry season found little active erosion and sedimentation but
numerous evidence from rainy season storms. In aggregate, similar erosion and sedimentation, much of
it the result of human activities, from the many hundreds of communities within the Rio Esmeraldas
basin have led to poorer water quality than what would be expected under natural conditions. In
addition, nitrates from fertilizers and fecal coliform bacteria from humans and livestock add to poor
water quality. Therefore, both sediment load and dissolved solids negatively impact fresh water
fisheries which could make a major contribution to the diets of the population within the basin.
Groundwater provides most of the potable and irrigation water resources for the Malingua Pamba
community. It surfaces at several natural springs at higher elevations in the community where it has
been directed to spring boxes feeding water lines which convey the water by gravity to most of the
community’s citizens. Tests by EWB – Denver have indicated that the untreated spring water is of
relatively high quality (including low levels of fecal coliforms) and is generally suitable for human
consumption with little or no treatment other than filtering for low levels of sediment
During the November 2006 visit, EWB-Denver analyzed potable water at selected locations for bacteria
counts, metals, and water quality parameters (EWB, 2009). Potable water samples were collected from
the high springs, the source water for the D-1 system(Figure 1-5), and from one location on the D-3
system. Water from the D-2 system was not analyzed. The results indicated no inorganic or metals
parameters of concern. However, the biological tests indicated low levels of E. Coli bacteria in some of
the potable water supplies.
Figure 1-5. Spring area for D-1 system located at approximately 3700-3800m elevation above
Q. Yanarumi. Area is fenced to keep out livestock.
In November 2007, additional water quality testing was conducted, focusing on the assessment of
coliform bacteria in potable water supplies. Results confirmed that potable water sources are of
reasonable quality although there were some exceptions. For example, the springs serving the Pucará
water distribution evidenced some E. Coli bacteria.
1.5
Soils
Most soils in the Malingua Pamba area are classified as Hapludolls (MAGE, 1983). These are fine sandy
soils are derived from pyroclastic materials on moderate to steep slopes (12 to 70%). They are black to
very black in the upper, organic horizon which may reach a meter or more in depth (Figure 1-6). In the
majority of years, the soil profile is dry for three consecutive months or less. Soil temperatures vary
from 10 to 15oC depending on altitude.
The rich upper organic horizon, mineral composition, moderate temperatures, and abundant rainfall
during most of the year result in soils that are very productive for agriculture and forestry. It took
thousands of years for these productive soils to develop under undisturbed cloud forests and paramo
grasslands in the extrusive volcanic materials deposited on the land surface. However, hundreds of
years of clearing the protective cover of vegetation for settlement, cultivation, and livestock grazing
have resulted in a loss of much of the original topsoil. What remains in much of the Malingua Pamba
area are less productive and less stable sandy subsoils soils with a thin or non-existent surface horizon of
organic topsoil (Figure 1-7). These sandy soils are more susceptible to surface water erosion especially
when stripped of a protective cover of vegetation.
Figure 1-6. Soil profile near Q. Yaranumi east of
Pucara has approximately 30cm of topsoil over
friable volcanic tuff.
Figure 1-7. Soil profile approximately 20m east
of Figure 1-6 location has less than 30cm of
topsoil over unconsolidated, fine volcanic sand.
1.6
Vegetation/Ecology
Two natural vegetation communities are present in the Malingua Pamba area: cloud forest at lower
elevations and grass páramos at higher elevations (Neill, 1999b).
Cloud forest is the montane rain forest which occurs on slopes of the Andes from about 2,500m
elevation to an upper limit of 3,400 to 3,600m. Only scattered remnants of the cloud forest remain the
Malingua Pamba area (Figure 1-8). During the course of human habitation of the area, much of it has
been cleared for agriculture, firewood, building materials, home sites, and roads. At this time, we do
not have specific information on the pre-settlement tree species of the Malingua Pamba area. However,
according to the Missouri Botanical Gardens research site (Neill, 1999b), central and southern
Ecuadorian forests between 2800 and 3200m are typically dominated by species of myrtle (myrsine), Ilex
(Clusia, Weinmannia), and magnolia. Throughout Ecuador, forests between 2800 and 3600m also
include species of Schefflera, Hedyosmum, and Oreopanax. Myricanthes, Weinmannia, Hedyosum, and
Oreopanax are recommended reforestation species (Borja and Lasso, 1990) and appear to be suitable
for the Malingua Pamba area.
Figure 1-8. Remnants of cloud forest on the lower slopes (elevation approximately 34003500m) of a mountain side located 2 km northeast of the Malingua Pamba community center.
The grass páramo, which occurs throughout the Ecuadorian Andes from about 3,400 to over 4,000m
elevation, is dominated by bunch- or tussock-forming grasses including species of reedgrass
(Calamagrostis) and fescue (Festuca). In some areas, the páramo is interspersed with copses of small
trees up to 4,100 m elevation. Many páramo areas are deliberately burned annually, or at least every
few years, by local farmers in order to maintain pasture for livestock (Figure 1-9). Therefore, páramo
plants have adaptations that enable them to survive the frequent fires (Lægaard, 1992). While some
burning still occurs in the Malingua Pamba community, there have been attempts to curtail this practice
particularly in the water supply watersheds (citation – personal communication with Pam, right?).
Figure 1-9. Páramo vegetation at 3850m elevation above Q. Yanarumi. Grasses in
foreground were burned, probably within the past two years.
1.7
History
There is no archaeological or historical evidence to indicate just how long the Malingua Pamba area has
been settled and farmed (true? Laura has heard about 100 years - ask Paulino) Archaeological evidence
indicates a human presence in the Ecuadorian Andes for several thousand years. From around 8000 to
2500 BCE, a variety of plants and animals were domesticated in the various environmental zones of the
Andes, and these became the basis for an agricultural society. The most important were potatoes,
maize (corn), beans, llamas, and alpacas (Bawden, 2011). By 1000 BCE, simple farming societies existed
throughout the Ecuadorian Andes (Wikipedia, 2010). Prior to the Inca invasion of the late 15th Century,
advanced indigenous cultures were present in the Ecuadorian Andes, and the area that later became
Cotopaxi Province was densely populated (Hip.Ecuador, 2011).
2.0
History of the Water System and EWB’s Involvement
Prior to EWB involvement the community had constructed a simple potable water distribution system
and partially installed an irrigation infrastructure. Lacking design data, access to materials, and
waterline construction experience, the potable water systems were characterized by very high pressures
in some areas, insufficient pressure in other areas, leaks, malfunctions and uncontrolled distribution.
The irrigation systems lack secondary distribution lines and required additional distribution and storage
tanks.
Pam Gilbert, a retired math teacher from Boulder, Colorado, has been involved with educational
and community development in Malingua Pamba for several years and founded an NGO (Centro
Educativo La Minga, www.escuelaminga.org) to support these activities. Among her accomplishments,
she obtained funding for and organized the building of the Escuela Minga, a secondary school (colegio),
in Malingua to serve the surrounding community. Pam Gilbert approached EWB-Denver in the summer
of 2006 for assistance in improving the water supply in Malingua Pamba so that, at the minimum, the
community shower at the colegio could be made operational, and, to address other potential water
supply problems in the village.
EWB-Denver made an initial assessment trip to the community in November 2006. They developed an
understanding of the problems and deficiencies of the existing water system and made plans to assist
the community in significantly improving and expanding it. The group also learned that common water
sources provide water to the communities of Malingua Pamba, Tunguiche and their associated sectors.
Between April 2007 and June 2010, EWB-Denver made an additional eight trips to the community to
assist the local people in making a number of improvements to the existing potable and irrigation
systems, construct additional water lines and pressure break tanks, and assess the success of these
improvements.
During these trips, the project teams noted the existence of erosion issues within the community.
During the last trip (June 2010) EWB-Denver trip to Malingua Pamba, Chris McLaughlin did a preliminary
assessment of erosion problems in four areas where erosion had occurred. He took notes characterizing
the nature and possible causes of erosion in those locations. In addition, he took GPS readings and
photographs at each of the sites and including photo documentation. The erosion observed by
McLaughlin had been caused by leakage from water system tanks. At two of the sites, the community
had planted “poles” of native luchero trees which were beginning to produce leaves. Conversations
with members of the community confirmed a genuine interest in solving local erosion issues.
3.0
Involvement of the SOIL Fund of IECA
The erosion problems at Malingua Pamba came to the attention of the International Erosion Control
Association (IECA) which is headquartered in Denver and is the world’s oldest and largest association
devoted to helping members solve the problems caused by erosion and its byproduct—sediment. IECA
connects 3,000 members who specialize in erosion and sediment control, storm water management,
and natural resource protection.
IECA has created a charitable organization called the SOIL (“Save Our International Land”) Fund. The
vision of the SOIL Fund is to further the science of erosion and sediment control and to improve the lives
of those impacted by soil erosion and sedimentation on land and in water bodies. The SOIL Fund
provides a permanent funding source for programs and projects that improve environmental quality
through education, research, and applied technology. The Fund has provided previous support to the
Tsurakú Project in eastern Ecuador (through an EWB chapter in Arizona), a water quality project in
western Kenya, a biological soil crust research and development project, and a reforestation project on
Easter Island, a Chilean territory in the South Pacific.
The SOIL Fund agreed to provide financial and technical support to an erosion control specialist who
would accompany the EWB-Denver team during its June 2011 implementation trip to Malingua Pamba.
This initial trip for the erosion control specialist would be for site assessment only. Implementation of
erosion and sediment control measures would take place during subsequent trips.
4.0
Reconnaissance Trip
The objective of the erosion control specialist was to document and assess the nature and extent of
erosion and sedimentation issues in the community during the June 2011 site assessment trip.
Secondary objectives were 1) to seek input from the community regarding local priorities for areas
needing erosion treatment and control 2) to contact and seek input from Jose Calvopiña, an agricultural
conservationist who provides conservation services and environmental education in the region and 3) to
determine the local and in-country availability of materials that can be used in erosion and sediment
control.
The objectives of the assessment trip were met and the following tasks were accomplished:
- Prior to the site assessment trip, members of the community compiled a list of areas with
erosion problems which they considered the highest priority for mitigation. This list was
provided to the erosion control specialist upon his arrival in the community.
- An extensive field survey was conducted documenting more than 60 areas in the community
with erosion and sedimentation problems. Included were most of the areas on the community’s
list plus several tank and water line sites recommended by EWB Engineer, Mark Richards, as well
as other sites observed by the erosion control specialist while walking and riding through the
community. This report includes observations, measurements, photos, and treatment
recommendations for 46 of those sites.
- The erosion control specialist made e-mail contact with Jose Calvopiña prior to leaving for
Ecuador. An initial lunch meeting took place in Latacunga on July 1, 2011 followed by a field trip
led by Señor Calvopiña to the community of Samil Pamba located approximately 10km
northeast of Malingua Pamba. The erosion control specialist accompanied Señor Calvopiña on a
tour of a Samil Pamba farm where sustainable, low-technology erosion and sediment control
methods are being successfully employed.
- The erosion control specialist determined that most of the low-technology materials needed for
erosion and sediment control are available locally or can be produced in Ecuador including seed
for grasses, seedlings for shrubs and trees, gravel and riprap, sand bags, and pvc pipe. In Quito,
he met with Jean Brown, an Anglo-Ecuadorian permaculture specialist. She feels that jute
netting for erosion control can be inexpensively manufactured by weavers in Los Elenes, a
community near the city of Rio Bamba.
Following the site assessment trip, EWB-Denver and the SOIL Fund need to assess the data and come to
an agreement on technologically appropriate and sustainable approaches to the erosion problems.
During a subsequent implementation trip, the erosion control specialist, ecologist, and other interested
EWB-Denver professionals would assist the community in the implementation of the proposed
solutions.
5.0
Summary of Findings
Erosion and sedimentation problems observed during the site assessment trip can be grouped and
prioritized according to the man-made structures and landscape features with which they are
associated.
5.1
Waterlines and Tanks
In general, the erosion control specialist has concluded that eroded areas with the highest priority for
treatment are those associated with waterlines and tanks, especially those for potable water. A number
of steeply sloping areas were observed where the integrity of waterlines is threatened by slope
movement or failure. In some areas, waterlines have been constructed across unstable steep slopes.
Whether lines have been buried or laid across the surface, both slow soil movement (soil creep),
catastrophic slope failure, or flash flooding can put pressure on the waterlines causing them to rupture.
When this happens, the affected residents lose their potable tap water forcing them to haul water
(usually by hand or by burro) until the rupture location(s) is/are identified, replacement pipe is
purchased in Latacunga and transported to Malingua Pamba, and the line is repaired by local plumbers
and laborers, a process that can take days or even weeks. Rupture of irrigation lines can also have
serious consequences especially during the growing season when irrigation water is critical to the
success of crops.
Erosion and associated flash flooding can also result in the loss of a pressure break tank. In April 2011, a
flash flood and debris flow in Quebrada Yanarumi in the southeastern corner of the community
destroyed a potable water line and a pressure break tank on the D-3 line which serves the Pucara and
Chilcaucu sectors (Figure 5-1). It took several weeks to rebuild the line in new location and restore
water service to these sectors. The erosion control specialist also observed that sandy soil is eroding
below the bases of some tanks which could eventually cause them to slip rupturing their input and
output pipes.
Figure 5-1. Flash flood and debris flow in Q. Yanarumi in April 2011caused an interruption
of potable water service to sectors served by the D-3 line which was subsequently relocated
south of this quebrada.
5.2
Roads and Paths
Erosion associated the community’s roads is disruptive to commerce and other essential travel to
neighboring communities, towns, and cities. There are four roads leading out of the community:
- the road south to Highway 40 which provides access to Latacunga (the provincial capital) and
the Pacific coast of Ecuador;
- the road north to Isinlivi where the closest medical facilities are located;
- the road through Tunguiche across Rio Toachi (via a new bridge) and west to Chugchilán and
other towns west of the river.
- an alternative 4-wheel drive road east to Latacunga via Samil Pamba.
All of these roads cross steep side slopes where large road cuts in soft volcanic sand often fail depositing
large accumulations of sand, rock, and vegetative debris on the road surface. This can result in road
closures until a bulldozer, backhoe, or road grader can be brought in from outside the community to
clear the road. The road south of Malingua Pamba was reportedly closed for several weeks in April 2011
following the flash flood and debris flow in Quebrada Yanarumi described above in Section 5.1. The
road between Malingua Pamba and Tunguiche was also closed by a slope failure (below the Chimbusi
sector) resulting from the April 2011 storms (Figure 5-2).
Figure 5-2. Road cut between
Tunguiche and Chimbusi after
massive, rain-caused slope failure in
April 2011and prior to major repairs.
Photo by
Slope failures on road fill slopes can have even more serious, long-term consequences if the erosion
migrates headword across the road surface. If the road surface disappears, import of new fill and road
base would be required and the road would need to be reconstructed.
Erosion also threatens the community’s network of pedestrian and livestock paths which are heavily
used since few residents own motor vehicles. However, this appears to be more of a temporary
inconvenience rather than a serious issue in most cases. Usually, when a path is damaged or destroyed
by erosion, pedestrian find a way around the problem area and create a new path which becomes well
established in time with use.
5.3
Cropland
Damage of cropland from erosion and sedimentation occurs often during the rainy season. Impacts
include gullying of fields, loss of topsoil, and potentially, even loss of part or all of a crop. If farmland is
fallow or newly planted with no protective vegetation present and the topsoil exposed, it is more
susceptible to erosion. Erosion and sedimentation can affect a family’s food supply although totally loss
does not appear to occur often.
Observations of cropland during the 2011 reconnaissance revealed some examples of erosion. This was
more evident in areas such as the Tinga sector with exceptionally sandy soils and little topsoil. It was
also noted that impacts were mitigated somewhat by cultivation practices. On sloping land, Malingua
Pamba farmers generally plow and cultivate along the contour (Figure 5-3). Even after harvest, the soils
are typically left in a roughened condition. This practice appears to reduce erosion and sedimentation.
Figure 5-3. Cultivation along the contour in the Pinali sector.
However, even contour plowing and cultivation are insufficient to prevent erosion and sedimentation
that occurs when concentrated stormwater follows swales and creates rills and gullies. Few examples of
terrace farming and stormwater diversion ditches were observed in the community. These measures
could prevent or minimize the possibility of concentrated stormwater flow destroying farmland through
the creation of rills and gullies.
A related impact to cropland was observed in several Malingua Pamba sectors where relatively flat
cultivated land on mesa tops is being gradually lost to headword erosion of steep slopes below the tops
of the mesas. Several examples were observed in Pucara, Chimbusig, and Chilcaucu. In some cases
farms have slowed this process by planting shrubs or not clearing natural vegetation along the lips of the
mesas.
Impacts of livestock grazing on erosion and sedimentation were not directly observed. It is generally
accepted that overgrazing in the United States has had a serious effect on erosion and sedimentation
when the carrying capacity of the land is exceeded. Grazing practices in Malingua Pamba may mitigate
the effects of erosion and sedimentation. There do not appear to be large concentrations of grazing
animals in the community. Furthermore, the farmers often tether the grazing animals to stakes and
move the stakes periodically to control the amount of grass consumed and keep the animals out of
quebradas and other areas where they could cause significant topsoil damage.
While erosion and sedimentation of cropland do not appear to be as serious a problem in Malingua
Pamba as the negative impacts to the water system and community roads, it needs to be addressed.
Most farmers in the community practice subsistence agriculture growing only enough food to feed their
own families. Thus, even a small loss of cropland in a community facing increasing human population
pressure is a concern.
5.4
Buildings
Buildings can be damaged or destroyed by headword and lateral gully erosion. For example, just north
of the Malingua athletic field, a large gully has laterally expanded to within two meters of a house.
Damage or potential damage does not appear to be a widespread problem as most residents have not
built homes or other structures close to stream channels or swales.
5.5
Rio Toachi Watershed
As noted above in Section 1.4, the aggregate of erosion and sedimentation from hundreds of
communities in the Rio Toachi watershed have led to diminished water quality in the Rio Toachi, its
tributaries, and the larger Rio Esmeraldas downstream (Figure 5-4). The greatly increased sediment
loads resulting from human activities northwestern Ecuador negatively impact fresh water fisheries.
Figure 5-4. View northwest of Chimbusi village and severely eroded cliffs on the
west side of the Rio Toachi. Note grass burning in progress in upper left of photo.
Obviously, reducing erosion and sedimentation in the Malingua Pamba community will have only a
minimal impact on the downstream quality of the Rio Toachi. Therefore, while improvement of water
quality within the watershed is an important long-term goal, it is beyond the scope of this project.
However, it is hoped that efforts for erosion and sediment control in Malingua Pamba can serve as an
example to other communities within the watershed and become the basis for a long term effort to
improve regional water quality.
5.6
Aesthetic Characteristics of the Area
Malingua Pamba lies just east of the Quilatoa Loop. This area, which centers on the Quilatoa Crater, has
been described in one popular guidebook as boasting “some of the most breathtaking scenery in
Ecuador, and is perfect for travelers seeking a taste of indigenous farm village life and spectacular
mountain landscapes a bit off the usual tourist path” (Viva Travel Guides, 2010).
While some tourists may find large erosion features spectacular, many “eco-tourists” would prefer to
see landscapes in which indigenous communities are living in relative harmony with nature. As with
watershed quality, aesthetics are a regional issue that cannot be solved by only one community.
However, if the people of Malingua Pamba want to welcome tourists interested in learning about an
indigenous Andean community which is actively improving its environment, a successful erosion and
sediment control program would be an important element in the model they could showcase.
6.0
Site-Specific Issues
As noted above in Section 4.0, this report includes documentation for 46 of nearly 60 sites visited which
have erosion and sedimentation issues. Information for each site, including photos and recommended
treatments, is found in Appendix 1. Figure 6-1 shows the site locations.
The site numbers are for GPS readings and correspond to the order in which sites were visited and are
unrelated to site priority. Of 108 GPS readings, 21 were taken at the elevation bench mark at the
community school, 14 (sites 74 through 87) were taken in the watershed area for the springs, and 5
were taken outside the community. Two GPS readings were taken at each of 7 of the sites (often one
reading at the upper end of a large erosion feature and the other reading at the lower end). A few
readings were taken at sites with no significant erosion/sedimentation issues. No GPS readings were
taken at sites 201-206. These latter sites were viewed from a distance.
Sites were subjectively rated according to their priority for treatment (Table 6-1).
Priority
High
High-Moderate
Moderate
Moderate-Low
Low
Table 6-1
Malingua Pamba Erosion Sites: Priority for Treatment
Number
Site Numbers
of Sites
09, 13, 14, 15, 16, 18, 20, 45, 49, 53, 63, 98, 99, 201
14
62, 65, 72
3
04, 10, 21, 22, 27, 37, 39, 41, 46, 48, 50, 51, 59, 60, 69, 71, 93, 96, 100, 101, 201, 202, 203, 204, 205, 206
25
42, 91
2
31, 32
2
Explanations for the priority rating for each site are given in the individual site tables in Appendix 1.
Sites were also grouped as to the man-made feature (or features) with which they were most closely
associated (Table 6-2).
Table 6-2
Feature
Water lines and/or tanks
Roads or paths
Agricultural land
Buildings or playgrounds
Malingua Pamba Erosion Sites: Associated Features
Number
Site Numbers*
of Sites*
13, 14, 15, 16, 45, 46, 50, 59, 60, 62, 63, 65, 71, 72, 91, 93, 98, 99, 100, 101, 201
21
04, 09, 10, 18, 20, 21, 22, 31, 32, 37, 41, 42, 45, 48, 49, 53, 69, 202, 204, 206
20
16, 18, 27, 42, 51, 53, 59, 71, 93, 101, 201, 202, 203, 205, 206
15
39, 96, 205
3
*Some sites are associated with two types of features
Table 6-3 groups the sites by associated features and their priority. For example, there are 9 “high
priority” sites associated with water lines and/or tanks.
Figure 6-1
Table 6-3
Malingua Pamba Erosion Sites: Number of Sites by Priority and Type of Associated Feature
Feature
Total No.
High
Moderate- Moderate
LowLow
of Sites*
High
Moderate
Water lines and/or tanks
21
9
3
8
1
0
Roads or paths
20
6
0
11
1
2
Agricultural land
15
4
0
10
1
0
Buildings or playgrounds
3
0
0
3
0
0
*Some sites are associated with two types of features
7.0
Summary of Solutions
As previously noted, one of the objectives of this study is to determine low-cost and sustainable
methods of erosion control which rely on materials which are locally-available or, at the least, available
in Ecuador. With this objective in mind, the following erosion and sediment control mitigation methods
are offered for consideration. No one method is applicable to all problem sites. Therefore,
recommended site-specific measures are presented in Appendix A along with photographs showing
existing site conditions and hazards.
7.1
Vegetation plantings combined with applications of topsoil and compost.
[Laura – please insert text]
Vegetation plantings including combinations of trees, shrubs, and grasses can be used at most of the
sites identified in the Malingua Pamba area.
Figure 7-1. Luchero tree plantings and sigsig (tall grass on right) next to an irrigation
tank located east of Tunguiche.
Figure 7-2. Chilka, an endemic shrub, growing next to trail between Malingua Pamba and Pucara.
7.2
Application of gravel, cobbles, and riprap
General Use: Riprap and smaller rock material (cobbles and gravel) can be used to dissipate energy and
prevent erosion in areas where flow of water is problematic due to concentration of flow or due to a
significant drop in elevation (such as at the end of a pipe).
Design Considerations:
 Riprap consists of rocks, broken concrete, or other material that is placed by hand or with heavy
equipment on a stream bank or other slope that is susceptible to erosion.
 Riprap should not be used on slopes that are steeper than 1.5H:1V.
 The depth of riprap should be two to three times the average diameter of the rocks.
Gravel, cobbles, and riprap might be used at the following sites in the Malingua Pamba area:
7.3
Quebrada Yanarumi main road crossing southeast of Malingua Pamba (site 09)
main road above (east of) Malingua Pamba (site 37)
Malingua Pamba primary school (site 39)
gully just north of Tanque Fiste (site 45)
main road north of Malingua Pamba (site 53)
about 150m above and east of Tunguiche church (site 65)
immediately north of Malingua Pamba next to main road (site 96)
Sand bags
[Laura or Rob please insert text]
Figure 7-3. Sand bags used to reinforce a stream crossing on road
several kilometers south of Malingua Pamba.
7.4
Road Drainage
General Use: To avoid washout of roadways and the fill slopes adjacent to them, culverts and roadside
ditches are constructed to pass runoff away from the roadway area. This runoff can come from the road
itself as well as the watershed above the road.
Design Considerations:
 Detail design of roadside ditches and culverts is commonly done on a site-specific basis and
requires the following information:
o An estimate of the total precipitation from a design storm, such as a 10-year event
o Drainage area
o Slopes
o Type of land use and cover in the contributing watershed.
 The minimum recommended size of a culvert is 24” diameter. Smaller pipes can easily become
clogged with sediment and other debris.
 Ditches can be trapezoidal or triangular (V ditch) in shape.
 Routine maintenance is imperative for proper functioning of these structures. Ditches along dirt
roads should be re-graded as necessary.
Road drainage improvements may be useful at the following sites in the Malingua Pamba area:
- along main road north of Tunguiche and below Chimbusi (site 18)
- Road to Tunguiche above (east of) Chimbusi (site 20)
- Road to Tunguiche above (east of) site 20 (site 21)
- Road to Tunguiche above (east of) site 48 (site 49)
- main road north of Malingua Pamba (site 53)
- road south of Chimbusi (site 202)
- Road to Tunguiche above (east of) site 48 (site 204)
7.5
Construction of check dams
General Use: Check dams are built across (perpendicular to) man-made ditches or natural channels to
reduce flow velocity in order to reduce erosion. They can be permanent structures or used temporarily
until vegetation is established.
Design considerations:
 Can be constructed as a concrete wall (approximately 0.3 meters in thickness) or using riprap or
boulders (Figure 7-4).
 The middle of the cross section can be a weir or just generally lower than the sides.
 Several of them are often used in series. Spacing depends on the channel slope as indicated in
Table 7-1.
 Sides should extend to the limits of the incised banks.
 They are not intended to trap sediment.
 They are not to be used in channels that receive continuous flows, but are for channels that
receive flow after precipitation events.
Figure 7-4. Concrete check dam (courtesy of Denver Urban Drainage and Flood Control District)
Table 7-1
Recommended Check Dam Spacing
Slope
2%
3%
4%
5%
> 5%
Spacing (m)
30
20
15
12
10
Source: CDOT, 2002.
Check dams might be used at the following sites in the Malingua Pamba area:
- main road north of Malingua Pamba(site 04)
- below main road north of Malingua Pamba (site 53)
7.6
Runoff Diversion Channels
General Use: These structures can be constructed by digging a ditch into the soil or by building a berm
above grade (Figure 7-5). They can be used for a number of functions, including:
 To divert runoff to a sediment pond
 To divert runoff away from disturbed areas, including cuts and fills along roadways
 To divert runoff away from crops, houses, or other property.
Figure 7-5. Diversion ditch at a mine site
in western Colorado. Photo by R. Zuber.
Design considerations are similar to those for roadway drainage.
 Detail design of diversion channels is commonly done on a site-specific basis and requires the
following information:
o An estimate of the total precipitation from a design storm, such as a 10-year event
o Drainage area
o Slopes
o Type of land use and cover in the contributing watershed.
 Ditches can be trapezoidal or triangular in shape.
 Berms should be compacted soil or course material such as riprap.
 Routine maintenance, including the removal of excess sediment and/or debris, is imperative for
proper functioning of channels.
Runoff diversion channels might be used at the following sites in the Malingua Pamba area:
- along main road north of Tunguiche and below Chimbusi (site 18)
- Road to Tunguiche above (east of) Chimbusi (site 20)
7.7
Discharge Water Spreader
At locations where concentrated discharge flow is creating gullies, the flow can be spread out,
converting it to less erosive sheet flow (Figure 7-6). This is especially useful for pressure break tank
overflow pipes.
Following are design considerations for a discharge water spreader:
-
The discharge point of the overflow pipe should be at ground level. Pipe elbows may be needed
to bring the pipe from the tank overflow outlet down to the ground.
A tee is attached to the end of the discharge pipe, and perforated pipe is attached to both sides
of the tee. It is recommended that the pipe have a row of perforations facing downslope.
-
-
-
-
The perforated pipe lengths would vary according to the width of the area (an agricultural field
or grazing land) where overflow water would be most useful. The perforated pipe would be laid
approximately perpendicular to the slope (along the contour).
The ends of the perforated pipe would be securely capped forcing the overflow water to
discharge through the perforations.
The optimal diameter of the perforations is not known but is suspected to be in the range of 2 to
5mm. It is suggested that flow through 2mm perforations be tested. The perforations could
then be enlarged if needed.
It is unlikely that the perforations would be regularly clogged with sand. The tank over flow
water would come from the top of the tank and much of the sediment would have settled to the
tank bottom. Also, the perforations would be along the side of the pipe and not on the bottom.
It is suggested that a row of geotextile fabric, 0.5 to 1m wide, be placed and anchored under the
perforated pipe sections to minimize any erosion caused by water discharging through the
perforations. Most of the width of the fabric would be on the downslope side of the pipe.
Alternatively, a row of gravel, 0.5 to 1m wide, could be placed on the downslope side of the
perforated pipe.
Figure 7-6. Rough schematic of a discharge water spreader.
Discharge water spreaders might be used at the following sites in the Malingua Pamba area:
- Tanque Tingo (site 16)
- Irrigation tanks near Tanque 9 (site 60)
- irrigation tank east of Tunguiche (site 65)
- Tanque Don Julio (site 91)
- Tanque 6 below Tanque Don Julio (site 93)
- irrigation tank on steep hillside east of Chimbusi (site 98)
- potable and irrigation tanks in Chimbusi (site 100)
- Tanque Bodega (site 101)
7.8
Erosion Control Fabric
[Laura or Rob please insert text. Refer to notes I previously provided re: Jean Brown, etc.]
Figure 7-7. Example of handmade erosion control fabric. Photo by L. Baucus.
Erosion control blankets could be used at the following sites in the Malingua Pamba area:
- Road to Tunguiche above (east of) Chimbusi (site 20)
- Road to Tunguiche above (east of) site 20 (site 48)
- Road to Tunguiche above (east of) site 48 (site 49)
7.9
Mulching
[Laura please insert text including Jean Brown’s opinions on pine boughs]
Mulching could be used at a number of sites to hold topsoil while newly-planted vegetation is getting
established.
8.0
Site-Specific Treatments
Table 8.1 provides site-specific, preliminary recommendations for materials and plantings needed at 44
sites evaluated in July 2011. The table groups sites by priority with the high priority sites first. Table 8-2
presents summaries of estimated materials needed for by each site priority grouping.
In the tables, figures for trees, shrubs, grasses, and erosion control material are for the estimated area
of coverage in square meters needed. Topsoil/abono (compost), riprap/boulders, cobbles, cobbles, and
concrete are given in estimated cubic meters required. Figures for discharge water spreaders and steel
pipe (or other materials to protect suspended pvc pipe across gullies) are for length of materials needed
in meters. Figures for diversion ditches are lengths in meters of ditches to be constructed. No specific
materials are needed to construct diversion ditches other than picks and shovels for hand excavation.
The combined estimate for coverage by trees, shrubs, grasses, and combinations of vegetation types is
15,421m2 (1.54ha) plus abono (compost), manure, or topsoil as needed. Obviously, hand planting such a
large area of vegetation would require an intense effort. Therefore, it may not be practical for the
community to plant the entire recommended area in one season. The community needs to be involved
in deciding which areas have the highest priority for planting in the first season.
Treatments are not recommended at the two low priority sites which are located along the Malingua
Pamba – Pucara road. This road is currently used only by foot and animal traffic due to several large
slope failures, most notably the one at Site 32. While the road has been reopened in the past by earth
moving equipment, repairs appear to be undone frequently by new slope failures. In the opinion of the
erosion control specialist, reconstructing and maintaining this road for the long-term across a very steep
and unstable slope would be prohibitively expensive given the resources available.
9.0
Implementing An Erosion and Sediment Control Program
9.1
Initial Program
The Malingua Pamba community can start immediately implementing an erosion and sediment control
program before deciding on priority areas for treatment and implementing any on-site mitigation. Pam
Gilbert, founder of Centro Educativo La Minga, has offered to work with Ignacio Sacotoro, principal of
the Malingua Pamba Collegio (high school) to start a plant nursery and seed bank in late 2011. Student
volunteers would be responsible for cultivating seedlings and gathering seed for native trees, shrubs,
and grasses to be used in erosion control efforts starting in 2012. The school currently has a small
(23mx10m) garden that can be used for this purpose (Figure 9-1), and expansion in other unused areas
near the school is possible.
Table 8-1
Table 8-2
Figure 9-1. Malingua Pamba colegio garden.
The erosion control specialist evaluated many sites which members of the community considered high
priority. They now need to evaluate the finding and recommendations of the specialist and decide
which areas with erosion/sedimentation problems should be addressed first. As noted above in Section
8.0, it is probably impractical to try to address all the identified problem sites in 2012. A new list of
priority sites should be prepared by the community prior to the next visit by EWB and the SOIL Fund
sometime in 2012.
The first erosion mitigation project will involve several steps once the nursery-seed bank program has
produced the necessary seeds and seedlings and the community has decided on a list of priority sites:
a. Obtain funding for materials that will need to be purchased from outside the community
b. Order any materials needed from outside the community such as riprap and pipe. Erosion
control fabric to be produced in Rio Bambo will need to be ordered several months in advance.
c. Have materials delivered prior to the scheduled start day for work
d. Make sure that sufficient hand tools (shovels, pick-axes, etc.) are available for the work
e. Hold training session(s) for community members who will be involved in the mingas (work
parties) which will perform the work. Consider employing the services of local agricultural
engineer, Jose Calvapiño, and permaculture specialist, Jean Brown to conduct the trainings.
f. Carry out erosion/sediment control measures at selected sites, under the direction of the
EWB/SOIL Fund volunteers. Consider also using Jose Calvapiño and/or Jean Brown to oversee
work at the first few sites.
g. Document the mitigation work performed with photos and notes.
h. Monitor the success and failure of the first year program in order to make any needed changes
in future mitigation work.
9.2
Parallel Program to Reduce Erosion Associated with Farming
As demonstrated in the nearby community of Samil Pamba (elevation 3700m), erosion and
sedimentation related to cultivation and grazing can be greatly reduced through the introduction of
terracing (Figure 9-2). Jose Calvapiño, an agricultural engineer based in Latacunga, is currently working
with several farmers in Samil Pamba who are practicing sustainable, organic agriculture using terraces to
improve topsoil and greatly reduce its loss through erosion and sedimentation. Some of the techniques
employed are as follows:
- Terraces are constructed along the contour by hand from the existing soil. Terrace width is a
function of slope angle: the steeper the slope, the narrower the terraces.
- Terraces are shaped to slope back slightly into the hillside causing some rain and runoff water
to pond at the back of each terrace. The water slowly infiltrates into the sandy soil and
percolates toward the front of the terrace providing soil moisture for crops.
- Shrubs and deep-rooted grasses (for example, pasto milim) are planted at the base of each
terrace and on the terrace face below. This vegetation helps anchor the terraces in place and
further slow the flow of water down the slope.
- Tall vegetation at the ends of the terraces combines with vegetation at the base and face of
the terraces to provide wind breaks which reduce wind erosion and provide protected microenvironments for each terrace.
- A mixture of crops including several types of potatoes and beans are planted on the terraces.
Monoculture planting is avoided. Cultivation is by hand rather than with machinery. No
chemical fertilizers or pesticides are used.
- Livestock are integrated into process to enrich the soil prior to planting. For example, on new
or fallow terraces sheep and goats are tethered to posts during the day and placed in pens
during the night. The posts and pens are moved daily resulting in a useful distribution of
manure in areas to be planted.
Figure 9-2. Successful organic farming with terraces in Samil Pamba.
It is recommended that a similar program be introduced in Malingua Pamba. The process could start
with a class showing the benefits of organic agriculture using terraces and include a tour of farms at
Samil Pamba. A demonstration project could be initiated in Malingua Pamba if a farmer can be found
who wants to participate. Alternatively, a demonstration project can be initiated by colegio students.
Jose Calvapiño and Jean Brown would be ideal professionals to provide education and oversight for a
demonstration project.
10.0
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