Bio-dyke protects Bangalipur community

April 26th, 2017

Healthy natural capital provides a buffer between flood hazards and communities. In flood emergencies it provides protecting ecosystem services and in normal time it is a livelihood resource. The vegetation growing along the strengthened river bank in Bangalipur, Bardia brings hope to at least 40 households and provides a site for others to ‘see and learn’.

There are 135 households living in Bangalipur; 40 households in this community are at risk of flood from the Aurahi Khola, a tributary of Karnali River.

The flood affects the community in three ways: it erodes the bank away and destroys agriculture and settlement; deposits sand and silt which damages harvests and makes it difficult to cultivate crops in the future; and during high flood events, the flood can inundate settlement leaving people homeless. Over the last 15 years the river has eroded three bigha (2.028 hectare) of agriculture land owned by 10 families rendering some of them landless. If this issue is not addressed the remaining 40 vulnerable household will be displaced.

Working in isolation, communities did not have the capacity to construct any kind of embankment. The Nepal Flood Resilience Project (NFRP) brought communities together and a representative body was formed – the community disaster management committee (CDMC) of Bangalipur.

The committee led a vulnerability and capacity assessment (VCA) which identified the Aurahi Khola riverside and nearby households as the most vulnerable to flooding. To address this problem the community identified the need to strengthen the embankment and flood defence structures and included it in their disaster risk management plan.
Although initial community priority was for high investment concrete structure or a pile of stone filled gabion boxes, they agreed on vegetative measures of bio-dyke technology using locally available resources and mobilising communities through the leadership of the CDMC. The project supported the communities in survey and design, cost estimate, funding for materials that needed to be purchased or hired and the communities provided the locally available materials and labour. A written agreement was reached in between the CDMC and the project outlining the objective, roles and scope of work for both sides.

River bank before constructing bio-dyke

The bio-dyke building
A junior engineer was brought in to technically advise and guide the work. Members of the community worked together to smoothen the bank slope between 30-45 degrees. A base foundation was dug out at the bottom of the bank slope. Then, grip walls were built in the foundation of sand bags supported with bamboo poles and systematically interlocked by gabion iron (GI) wire. These tow walls used 12 ft long bamboo poles in two rows running parallel at one metre and each driven into 8 ft deep holes dug by a driller and sand bag piled in between.

Piling sand bags along the slope to construct the bio-dyke

At every 20 m intervals along the bank, bamboo spurs (3 m long, 1.5 m wide and about a metre high) were constructed in the same way – filled with sandbags to deflect water flow away and to prevent water directly hitting the embankment. Sand bags were then piled up along the smooth bank slope – they were guided and interlocked with bamboo poles and GI wire. Lastly, the sandbags along the bank slope were covered with top soil in between hedge rows at 1-2 metres. Before the onset of monsoon (the growing season), locally available seedlings were brought from nurseries and transplanted on the slopes. The plants included bamboo, Napier and bushes that establish and extend their root systems rapidly. Bamboos were chosen at the face – the tow wall side. The community put a hedgerow of plants to prevent the slope from grazing and trampling. The community members monitored the area and prevented grazing.

Opportunity to test
The bio-dyke aimed to stabilise the 220 m river bank protecting about six bigha (4.056 hectare) land of 10 families. On the 26 July 2016, one of the biggest recorded floods in the river occurred, providing an opportunity for the community to test the strength of their structure. Although the dyke is yet to naturally stabilise to attain its full strength, it defended the flood well without major damage. The flood was 3 m high and rose over the bioengineering structure but there was no bank cutting and the land at the back was well protected. “There’s also less sand and silt brought in our field,” said Namrata who is one of the land owners. The coordinator of CDMC is ‘pleased to see the success’ and said, “We will extend the dyke further.”

After bio-dyke construction at Bangalipur, Bardia

The process built capacity within the community on how to build a bio-dyke. One hundred and thirty five community members worked on the process and have learned how it is done, increasing their awareness on the importance of riverbank protection. “We are now confident, we can do it,” one of the CDMC members said. He informed us that they are approaching local government to advocate for funding allocation to extend the embankment but the ongoing restructuring and elections may ‘lead to waiting for another fiscal year’.

All information of this story were collected by Buddhi Kumal, Lok Pokharel, Narayan Ghimire and Prakash Khadka.

6 responses to “Bio-dyke protects Bangalipur community”

  1. John Says:

    It’s really good that the community is engaged in protecting their homes while educating them on how to do it. I’m quite impressed with the finished bio-dyke. I hope they can continue protecting their homes.

  2. David Durston Says:

    A great story,but why print it in a faint grey typeface that makes it tiring to read. It is rood story : be bold in printing it.

  3. Margaret Johnson Says:

    Heartwarming that the community was able to organise to work together on this great project. Hopefully they could raise money between them or secure a loan from microfinance to get the next stage under way.

  4. Victor njeru Says:

    Great work – very simple and cost-effective.
    A question : do you have any scientific facts and formulae to support the structural strength of the dyke . Am also impressed that it worked. What’s the retained water depth? Surrounding Soil type/ borrow pits, deposition, etc. More information please. Thank you

  5. Nicola Says:

    What a great story. I found it very interesting that the bank supported provided protection even though the flood went over the top – it is preventing the erosion that is the primary goal.

  6. Dinanath Bhandari Says:

    Yes Nicola. Thank you.

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