Two months after 8 consecutive floods landed in Hoi An area in October and November 2020, the bank of Thu Bon river of Triem Tay village in Dien Ban town, Quang Nam was still in ruins. The lush, green two-year-old forest was almost dead when, leaving dry branches mixed with garbage from upstream pouring in, accompanied by the fishy smell of dead fish.
“Trees soaked in water for 20 days cannot survive,” said landscape planner Ngo Anh Dao, who has planted dull forests along the 650m long shore of Triem Tay and neighboring Cam Kim commune since 2018. Sad is sad, she said, but this is the law of nature.
The cork tree is the body
According to TS. Ngo Anh Dao is “a pioneer tree and a sacrifice for the posterior generation behind.” As a result, although the number of poor trees is only 1/3, the riverbank of Trem Tay village does not erode like in the previous years when floods came.
This poor forest is the outermost layer of an ecological soft embankment coping with landslide. Anh Dao put it to the test at her farm An Nhien after the historic flood in 2017 seeped 12ha of the riverbank area. Before the embankment was constructed, each time the flood came, the banks of the Trem Tay River would recede more than ten meters deep and many villagers determined that they would have to leave sooner or later.
TS. Ngo Anh Dao, the concept designer of the ecological embankment. Photo: Yen Duong
The ecological soft embankment model is the result of many years of observation and research by TS. Anh Dao goes downstream of Thu Bon river. She does not consider this as a new invention but simply a process of restoring indigenous ecosystems.
“This is a very sensitive and fragile area,” said the female landscape planner, when she was under pressure from the water pouring in from the Truong Son mountain range, and the pressure from waves and storms. Just comparing the map of Thu Bon river basin from 1984 with the present, anyone can recognize the appearance, swelling and disappearance of floating dunes. If more than 30 years ago, there were four large and small sand dunes in front of Trem Tay, over time, the side of the mudslide, now they have formed a large dune deviating to the north, causing the flow from upstream to crash into the bank of Trem Tay village and the neighboring Cam Kim commune. Therefore, every time the flood comes, the Trem Tay bank will slide and the other sand dune bank accretes.
The villagers of Trem Tay seem to be too familiar with this harsh law of nature. At the age of 54, Pham Duoc had to move his house twice despite being born and raised in this village. His first home was at the head of the village but by the age of twenty, he was forced to move to the middle of the village. In 2009, the commune authorities urged him to continue to move, but because of “comfortable housing, a garden, a chicken”, he decided to stay. However, after the historic flood in 2017, when the water flooded to 1.6 meters deep, he got scared and decided to demolish the house, sell the land and move to his current home at the end of the village.
“I wanted to build a house to leave for the children, so I accepted it,” he was told. Each time like that, he “is not sad” because “has to accept it.”
Also because of the desire to keep the village and have a passion for planting trees, this builder began to work as TS’s farm housekeeper. Anh Dao from 2016 on a piece of land at the end of the village abandoned because some people have retreated inland like Mr. Can. Others, especially the young, have quit farming because their rice land is either no longer available or salty, and go to work on tourism in Hoi An or Da Nang.
On this wasteland, Mr. Can and other workers have built wooden houses with modern designs, combining the high structure of stilt houses with indigenous materials such as bamboo and grass. The houses are mixed with nursery gardens and research of diversity of plants.
Standing from the house overlooking the river bank is a bamboo forest that villagers planted in the 1980s to prevent floods. “Thanks to this bamboo forest, when the flood comes, the flow will decrease”, he is explained. “Like when water runs through that basket.”
In front of the bamboo forest, along the riverbank is the ecological embankment.
Use “soft” against “hard”
Different from the commonly applied concrete hard revetment in Vietnam, the soft revetment does not resist the destruction of waves and floods but backs and accepts it – more similar to the village motto of living with floods. This 200 years old.
“The current popular philosophy is that people are fighting against nature, conquering nature with hard solutions and ignoring the understanding of coastal ecosystems, the access between water and land”, PhD. Mr. Dao analyzed. “Thinking like conquering nature, using it hard against the power of nature will be terrible because its destructive power will be even greater.”
Principle TS. Cherry mentioned that the law is immutable in physics: punching a wall with your hand will always hurt more if you punch the mattress with the same force. And given the increasing intensity and destructive power of storms and floods due to the effects of climate change, new coping measures are becoming more and more imperative to minimize damage from dike breaks.
Illustration of three-layer ecological soft embankment used to cope with the landslide of TS. Ngo Anh Dao. Illustration: lambinh
In the design of the ecological embankment, the cork tree is TS. Cherry brought back to plant from Quang Tri, is the outer layer of the buffer protecting the village shore. The roots of this plant are of two types. The main root is poked straight down, possibly up to ten meters deep. The secondary roots, also known as lung roots, are precipitated when immature, soft and swaying with the waves. When the tree grows, this lung root hardens, protrudes from the mud about 60-80cm, very hard. Therefore, cork trees have the ability to accumulate mud, hold soil, and reduce the destructive power of underground waves.
Next to the cork layer is a layer of grass, including native grasses such as hammer grass, grass with bald roots that can be up to 3m deep below the ground, next to the pangasius is a two-leafed tree, the roots are even deeper. tens of meters. These are easy-to-live, fast-growing plants with good soil holding capacity.
The last layer is a row of casuarina trees planted from 2017 that are 8m high. In addition to the ability to hold soil, the height and softness of the conifers help to both block waves and windbreak.
These three layers together create a green vegetation reinforced with bamboo biological “lock” layers to support soil retention in the early years when the layers are young, the roots are not deep enough.
With the initial results achieved, TS. Anh Dao is confident that the philosophy behind this model is the right direction for the sensitive downstream areas that are suffering from both natural disasters and natural disasters. The flood discharge of dozens of hydroelectricity upstream; exploitation of sand in the river bed; monoculture agriculture, improper exploitation of groundwater, causing subsidence; along with tourism development, regardless of the fragility of the ground here, all contribute to increasing the risk of landslides in the area, he explained.
Natural balance
Realizing the initial efficiency of the project, in addition to the affordable price – the construction cost of 1 meter of ecological embankment is only 1/5 of the cost of building the concrete embankment – Hoi An government plans to extend 900m of longitudinal embankment. According to the territory of Phuoc Thang village in the neighboring Cam Kim commune, where after the flood in 2017, the bank fell 50 meters deep into the mainland.
However, the ecological embankment is not without its risks. “An embankment requires a tree to develop to a certain extent to be effective,” said Nguyen The Hung, vice president of Hoi An city. This is a fact to consider when choosing the time to start planting trees for ecological embankments because according to the experience of the Hoi An people, every three to five years a big flood will repeat and the poor forest also needs that many years. to be able to cope with floods.
The most obvious evidence is the initial failures in the construction of ecological embankments by TS. Cherry. In fact, the horticultural forest she planted in 2018 was the second test after the failure of 2017, when the historic flood hit and killed the immature cork trees that were only one year old.
Pham Duoc, born and raised in the village of Trem Tay, had to move his house due to the impact of floods and landslides. Photo taken on January 26, 2121 in Trem Tay village (Dien Phuong, Dien Ban district, Quang Nam province). Photo: Yen Duong
Therefore, each ecological embankment requires a deep understanding of the local soil and climate. Invited by the authorities of Dak Nong and Dak Lak to study the replication of an ecological embankment model for the Krong No riverbank, which is suffering from severe landslides, PhD. Anh Dao cannot carry the whole model from An Nhien. The key thing that does not change is the principle of using measures of “soft, back and forth” instead of “forward and conquer”.
Post-flood cleaning in An Nhien continues after Tet. Meanwhile, the poor forest has begun to show signs of revitalization. “Maybe I will leave it alone, the cork tree will grow back on its own, or I will plant more, depending on the budget”. Anh Dao said.
What is important according to the doctor is the long-term perspective. Once the embankment ecosystem is returned to its natural equilibrium, other social and economic benefits will follow.
Since the ecological embankment, shrimp, fish, birds, wild ducks, many insects have created a new source of livelihood for the village. Each spring, “so many birds can not sleep at night,” he shared. The green embankment on the transparent river also contributes to attracting more tourists to visit this ancient village.
If before 2015, Trem Tay land was sold for 1 million / m2, not many people bought, now, the land price has increased 15 times thanks to community tourism projects, resorts and the belief that village land will is kept. Walking around the road surrounded by the tea tree fence of the village, you can see that people are taking advantage of repairing and repainting their houses to make them more stable and spacious. From the past two years, young people working away from home have come back with plans to do tourism and open shops. All just wait for the disease to pass to be ready to revive.
Le Giang Lam
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(This article is supported by the Rainforest Press Foundation in partnership with Pulitzer Center)
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