India has a coastline of more than 7,500 km. What this means in climate change terms is that people living along this coastline, particularly along the cyclone-prone Bay of Bengal, are vulnerable to the fallouts of climate change such as sea-level rise, saline water ingress and increasingly frequent severe cyclones. A method the Indian government has adopted to deal with such impacts is the construction of geotextile tubes. Geotextile tubes are engineered structures that are tube-like sacks filled with sand and sometimes covered with gabions--a wire box filled with small rocks. They are usually constructed between the high- and low-tide lines.
"Coastal erosion is [happening] because of events like cyclones and storms which are occurring more frequently nowadays because of climate change. Geotextile tubes is a mitigation measure," said R. Sundaravadivelu, professor in the ocean department at the Indian Institute of Technology, Madras (IIT-M). "It is for the protection of the coastline in places where the soil is too weak to take the weight of stone [embankments]." Embankments may comprise bricks, stones or concrete and are frequently used as flood defense systems.
Given the frequency and intensity of cyclones and storms, are geotextile tubes effective in mitigating the impact of climate change? For how long can these geotextile tubes hold against the vagaries of weather and at what cost? IndiaSpend surveyed the existing geotextile tubes and spoke to experts and locals to find the answers.
India's two geotextile tubes
India has two geotextile tubes. One is in Uppada, a village near Kakinada, the headquarters of Andhra Pradesh's East Godavari district. This was the country's first geotextile tube; its construction began in 2007 and was completed in 2010. The other is in Pentha, a village in Kendrapara, Odisha. Both Uppada and Pentha were severely eroding villages. Sea erosion at Pentha is about 10-15 metres per annum, according to a report by IIT-M. Erosion at Uppada is around 1.23 m per annum, found the researchers at Andhra Pradesh Space Application Centre.
IIT-M was the project consultant for both the geotextile tubes. Sundaravadivelu was part of the IIT-M team that was in charge of the geotextile tubes design.
There's also a submerged variant of the geotextile tube in Kadalur, Tamil Nadu. "This was built by the National Institute of Ocean Technology (NIOT) about two-three years ago as an experimental project," Sundaravadivelu explained. But as a sea-erosion mitigation technique, geotextile tubes in India are "not experimental", he said, adding that while there is scope for additional research and analysis, geotextile tubes are "an established technology".
IIT-Madras has also made suggestions to build a geotextile tubes in Sagar Island in West Bengal.
The cost of constructing a geotextile tube
The geotextile tubes in Uppada cost about Rs 16 crore, according to Ummudi Jaan, the sarpanch who oversaw its construction. The one in Pentha cost almost Rs 33 crore, according to a Right to Information (RTI) reply received by this reporter. And the geotextile tubes proposed to be built in Sagar Island is set to cost Rs 77 crore.
"Compare this to real estate value, cost of water-logged and saline paddy fields, roads and highways lost to the sea, loss of land in villages where people stay… land is precious and has to be protected from erosion," Sundaravadivelu said.
Amphan, the super cyclone that hit India in May last year, ranked fourth in the 2020 global list of climate disasters that resulted in widespread financial damages. It was also the costliest tropical cyclone of the year, with losses amounting to more than Rs 95,386 crore in cities in India, Bangladesh and Sri Lanka, IndiaSpend reported in December 2020.
State of disrepair
IndiaSpend found that maintenance work at geotextile tube sites has not been carried out at regular intervals, thereby reducing the effectiveness of both the geotextile tubes. Scientists and locals also noted fallouts such as increased erosion in areas lying beyond the geotextile tubes.
Construction of the geotextile tube in Uppada began in 2007 and was completed in 2010. The executing authority was the irrigation branch of the water resources department of the Andhra Pradesh government.
The geotextile tube is about 1.5 km long of which 500 m washed into the sea about three years ago, the locals told us. The rest lies in tatters and is beyond repair. "It [geotextile tube] is fully damaged. It is not useful now. It will not protect us," said Sathibabu, 39, an Uppada resident, who goes by his first name. He noted that there are 15,000 households in Uppada. Earlier the state government would undertake "patch work" but in the last 10 years "even that has not been done", he added.
"This needs immediate attention," Sundaravadivelu said, after looking at the photographs shared by IndiaSpend. "Surveys have to be conducted every year and maintenance has to be carried out every five years. We [IIT-M] had suggested a scheme under which maintenance should be carried out. It doesn't look like this has been done."
As for the 500 m tube that has washed away into the sea, he said "vandalism" could very likely be a factor. But in general, he explained, geotextile tubes have a life of only 20 years.
"These observations [about the tattered state of geotextile tubes] are correct," said Tiru Kulkarni, president, geosynthetics division, Garware Technical Fibres Ltd (GTFL). GTFL was the contracting agency in charge of constructing the geotextile tubes at Uppada and Pentha, and Kulkarni oversaw the construction of both. "Maintenance is a key component but it has not been given the kind of importance it should have been. What we are looking at is the power of the ocean which is quite immense. The structure [geotextile tube] is subject to tidal conditions day in and day out which are severe especially during monsoons."
IndiaSpend contacted Aditya Nath Das, principal secretary, department of irrigation, government of Andhra Pradesh, requesting for an interview. This department is responsible for the geotextile tube's upkeep. This copy will be updated if and when a response is received.
The brunt locals have borne
In October 2020, there was a depression in the Bay of Bengal, and many houses close to the beach in Uppada village--lying within the damaged 500 m of the geotextile tube -- were damaged due to strong winds, said D. Prasad, another resident of Uppada.
"Each time a cyclone hits the Bay of Bengal coast, Uppada sees [its] impacts," said N. Veerabhadra Rao, development associate, M.S. Swaminathan Research Foundation (MSSRF), Chennai. Rao noted how precarious the lives of people living along the Uppada coastline are given how the Bay of Bengal has become a hotbed for tropical cyclones. "During depression, wind speeds are about 50-70 kmph," he said, explaining how there can be significant damage even if depressions don't go on to form cyclones. Cyclones entail much greater wind speeds, over 80-100 kmph.
"We live in the mouth of the sea and it slowly keeps coming inward. It has come inwards by around 100 m in the last 50 years. A lot of land has already gone into the sea," said Balraj, 60, Uppada resident. He echoed Sathibabu's statement that many in Uppada want to be relocated to a safer place.
"We want to be shifted to another place. We wrote letters to the MLA [Dorababu Pendem] three months back [October]," Sathibabu had told us.
"In the last few years, many houses [close to the shore] are getting damaged because the geotextile tube is damaged," said T. Kondamma (60). In the last 20 years, Kondamma has lost three of her houses to the sea.
Overall, in the last 40 years, around 1,500 houses, two government guesthouses, a bus stand and some temples have gone into the sea, said Ummudi Jaan who was the sarpanch of Uppada from 2006 to 2011. "Ours is the first geotextile tube in the country. It cost Rs 16 crore. It has controlled erosion here but now one section [of the geotextile tube] has gone into the sea. Since construction, no repair and maintenance work has been carried out. Now the tube is damaged. It cannot be repaired. It has to be replaced. Cost will be around Rs 200 crore."
Looming threat of a disaster
Construction of the geotextile tube at Pentha began in 2013 and was completed in 2016. The project was executed by the Odisha Water Resources Department (WRD) with funding from the World Bank's Integrated Coastal Zone Management Project (ICZMP).
"At the time of [the geotextile tube's] construction, the shoreline at Pentha had advanced by 600 metres compared to where it was in 1975," said Jugal Kishore Tripathy, ex-executive engineer at WRD, Odisha. Tripathy oversaw the construction of the geotextile tube.
This geotextile tube is relatively well-maintained but is in tatters, too, at some places.
"We built this house after the geotextile tube was constructed but now we don't feel safe. The rocks are getting washed away," said Kaikeyi Rawat (45).
Similarly, Gayadhar Behera (63) built his house after the geotextile tube was constructed. "We feel safe now but there should be bigger stones [as embankment]," said Behera, whose house is 300 m from the sea. 'Bigger stones' refer to tetrapods like those on the Marine Drive in Mumbai.
"They [people living in Pentha] are farmers and plumbers who used to live in thatched houses and shift [inwards into the land] when needed. Around 3-4 years back [after the construction of the geotextile tube], they started building pakka houses," said Ashis Senapathi, a Kendrapara-based journalist.
After visiting Uppada beach and seeing the [state of the] geotextile tube, I know what will happen, Senapathi added, noting how the broken geotextile tube in Uppada barely offers the kind of infrastructural protection that villages along the coast require.
Assessing resilience of geotextile tubes
"We continuously monitor the geotextile tubes. In Pentha and Uppada, there is an accretion of the shoreline, maybe about 100-200 metres," said Sundaravadivelu, explaining that the shoreline has advanced into the sea, as opposed to the erosion that was happening earlier. "Erosion has been controlled and the spillage of water into land areas like roads and houses adjacent to the coastline can be avoided," he claimed.
Tripathy, too, said that there is sand accretion at Pentha.
But these claims are disputed.
"Erosion is still happening at Kakinada. Every time there is a cyclone, waves come onto the [Uppada beach] road," said Y.R.S. Rao, head, deltaic regional centre, National Institute of Hydrology, Kakinada. The road is located 30 m from the sea. "The geotextile tube [at Kakinada] has also sunk into the sand."
"There is no sand accretion in Pentha. The geotextile tube was supposed to help with sand deposition and coast stabilisation but this is not happening," said Biraja Pati, advisor, Nature's Club, a Kendrapara-based volunteer-run environmental and social organisation.
Geotextile tubes also come at other costs like increased erosion in areas that lie outside the length of the geotextile tube. "There has been a lot of erosion near Konapapapeta since the time the geotextile tube was constructed," said Jaan. Konapapapeta is located about 10 km from Uppada.
"If you stand on the road and look to your left, you will see a lot of erosion north of the geotextile tube. Before, the erosion was here [in Uppada]. Now the erosion site has shifted," Pati added.
Sundaravadivelu disputed these claims. "There are no negative erosion impacts [like increased erosion in areas that lie beyond the geotextile tube when the structure is parallel to the coastline," he said, adding that the adjacent coasts may erode "because of other, natural reasons".
Not all experts agree.
"During south-west monsoons when there are high-wave energy conditions and waves approach obliquely from the south and south-west, such structures [geotextile tubes] reflect waves onto areas lying to their north," explained Nageswara Rao, professor emeritus, department of geo-engineering, Andhra University. "So, erosion [in areas lying in the north of such man-made structures] is bound to happen," he stressed.
Konapapapeta also lies north of Uppada.
"To a certain extent this [increased erosion in areas lying outside the length of geotextile tubes] is true. When you strengthen a part of the beach, the waves tend to attack the next weakest part," said Kulkarni of GTFL. "It should be possible to study this and design the periphery of the geotextile tube in a way that this effect is mitigated."
This phenomenon of increased erosion towards the north of engineered structures within 3-5 years of construction has been observed in other places too. "We have seen this in Ennore port [in Chennai], in Visakhapatnam and in Odisha. This is what happens if you don't pay attention to wave dynamics while building ports and structures like geotextile tubes," told Rao, adding that the beach is also lost while noting that beaches are "part of the sea, not the land" given how wave activity extends into the beach.
Natural protection still better than engineered structures
For long-term protection of coastlines in an increasingly turbulent Bay of Bengal, natural solutions would work best, experts say.
"Any coastal protection is not a long-term solution. It has its own life," Sundaravadivelu said, referring to geotextile tubes, and making a case for preserving mangroves. "Wherever mangroves are growing naturally, we should not destroy it. This is much better protection than anything else."
Kulkarni concurred that mangroves offer the best coastal protection. "This is because mangrove roots run very deep and the way they grow, they act as a soft barrier for waves and break wave energy," he explained.
During the 1999 super cyclone that hit coastal Odisha, villages located in the shadow of mangroves suffered less damage than those located within embankments and those which had neither mangroves nor embankments, according to a study by the Wildlife Institute of India (WII). WII is an autonomous body under the Ministry of Environment, Forests and Climate Change (MoEFCC).
One criticism he had of geotextile tubes, Tripathy said, was that "it's too costly for us [state of Odisha]", pointing to a need to look to other solutions, including planting mangroves. "In the 1970s, Pentha had mangroves," he said.
It is 100% true that mangroves are better at protecting the coast than any artificial structure, Senapathi noted. "The area where the geotextile tube is [located] was also a mass Olive Ridley turtle nesting site. In 2003-04 around 50,000 turtles laid eggs there. Natural areas are always better and they should be maintained that way."
Vishal Bhargav contributed to this story with satellite imagery.
This story was produced with the support of the Earth Journalism Network through our Bay of Bengal Climate Resiliency Initiative. It was originally published in IndiaSpend on 25 May 2021 and has been lightly edited for length and clarity.
Editor's note: This story was updated on 9 June 2021 to replace the trademarked name for the erosion mechanism, geotube, with the generic name, geotextile tubes.
Banner image: A geotextile tube at Pentha village in Odisha's Kendrapara district / Credit: Rishika Pardikar.