Geotextile Tubes for Riverbank Protection Under the Namami Gange Mission

The Ganga and its tributaries erode their banks along long stretches of their course. Every monsoon, high flows cut into soft alluvial soil, taking farmland, homes and embankments and carrying huge volumes of sediment downstream.

Stable banks support the goals of the Namami Gange Mission, and sand-filled geosynthetic containers are now widely used to protect them. Geotextile tubes, along with the smaller geobags, let engineers build heavy, flexible bank protection from river sand instead of quarried stone.

This article explains how geotextile tubes are used for riverbank protection in the Ganga basin, how the technology works, and what to look for when specifying the materials.

Namami Gange: A Mission to Rejuvenate the Ganga

The Namami Gange Programme is the Government of India’s flagship programme to clean and protect the river Ganga, run by the National Mission for Clean Ganga. It was launched in 2014, and in 2022 the UN named it one of ten World Restoration Flagships under the UN Decade on Ecosystem Restoration.

Its second phase, Namami Gange Mission-II, has a budgetary outlay of around 22,500 crore rupees and runs to March 2026. The mission covers:

• Sewage treatment
• Industrial pollution control
• Riverfront development
• Biodiversity and afforestation
• Protection and stabilisation of the riverbanks

Why Bank Protection Matters for a Clean River

Eroding banks put large quantities of silt into the water, destroy riverside habitat, undermine the ghats and embankments that communities depend on, and displace riverside families.

Controlling that erosion quickly, at reasonable cost and with little environmental damage is a job geosynthetics do well. Geotextile tubes and geobags are now used for river and shoreline protection in many Indian states, from West Bengal and Bihar in the Ganga basin to Assam and Gujarat.

The Riverbank Erosion Problem on the Ganga

The Ganga and its tributaries are large, sediment-laden rivers flowing across flat alluvial plains, and their banks are made of the same soft silt and fine sand that the water carries so easily.

During the monsoon the discharge rises many times over, flow velocities increase, and the river attacks its banks. It undercuts the toe of the bank below the waterline, and once the toe is gone the soil above caves into the river in large slumping blocks. In meandering reaches the river shifts sideways year after year, cutting away land on the outer bends.

Why Traditional Methods Fall Short

Traditional protection relies on boulder pitching, stone aprons and concrete revetments. The Gangetic plains have almost no natural rock, so every boulder has to be quarried and hauled hundreds of kilometres, which is expensive and carbon-intensive.

Rigid stone and concrete structures are also brittle: when the river scours the bed at their toe, they are undermined and collapse. Bank protection on these rivers needs to be:

• Heavy enough to resist the flow
• Flexible enough to follow the scouring bed
• Permeable enough to relieve water pressure
• Buildable from materials available on site

A geotextile tube meets all four.

Geotextile Tube Technology: How Geotubes Work

A geotextile tube, often called a geotube, is a large tubular container made from high-strength woven geotextile, designed to be filled with sand and to hold its shape under river flow. Ocean supplies geotubes for river, coastal and dewatering work.

Filling and Consolidation

The empty tube is positioned along the bank or bed, and a slurry of sand and water, usually dredged from the river itself, is pumped in through filling ports spaced along the crown.

The woven geotextile has a controlled pore opening that keeps the sand inside while the water drains out through the fabric. As it dewaters, the tube consolidates into a dense, heavy, stable mass, and repeated fill cycles bring it up to its design height.

Deployment Configurations

Once filled, a geotube is a large single unit, often several metres across and tens of metres long, that resists the drag and lift of the flow by its weight. Tubes can be:

• Laid as a continuous revetment along the bank
• Stacked in pyramids to form larger bunds and dikes
• Built out into the river as groynes and spurs that deflect the current away from a vulnerable bank

Because they are flexible, tubes settle with the bed instead of cracking, and because they are permeable, they relieve the pore-water pressure that damages rigid structures.

A geotube is filled with locally dredged sand instead of imported rock, so on an alluvial river it is much faster and cheaper to build. On the Ganga, where dredging is already part of river management, the same sediment can go into bank protection.

Geobags for Scour Protection

Geotextile tubes are usually paired with geobags, smaller sand-filled geotextile containers that handle the parts of the job a large tube cannot.

Geobag riverbank protection works on the same principle as the tube, a permeable geotextile skin holding a mass of sand, but the bags are small enough to place by hand or drop from a barge to armour specific zones.

The Role of Geobags at the Toe

The main role of geobags is toe and scour protection. The biggest threat to any bank structure is the river scouring the bed at its foot, so a launching apron of geobags is laid along the toe.

When the river scours the bed, the bags at the edge of the apron roll down and cover the newly exposed slope, which stops the scour advancing. This falling-apron behaviour adjusts itself to the scour depth, which a rigid apron cannot do, and it protects the foundation the geotubes stand on.

Geobags are also used for:

• Filling the gaps between and behind tubes
• Building up levels
• Repairing and reinforcing existing structures

A geotube core with a geobag apron and infill makes a flexible bank protection system that adjusts as the bed changes, which is why the two are often specified together.

Woven Geotextiles for Filtration

Filtration and Separation

Beneath and behind the sand-filled units sits another layer: the woven geotextile filter. Before any tubes or bags are placed, a filter fabric is laid over the prepared bank and bed.

Its job is filtration and separation. It lets water pass freely while holding the fine foundation soil in place, so the river cannot wash bank material out from under the protection, a process called piping.

Without this filter, water moving in and out of the bank as the river level changes would gradually flush away the fine soil and hollow out the foundation until the structure settled or failed.

Fabric Engineering and Testing Standards

Woven geotextile is also the material of the tubes and bags themselves, so the fabric has to retain the sand fill and withstand abrasion from sediment-laden flow for its design life. These fabrics are specified and tested for:

• Apparent opening size: ASTM D4751
• Water flow (permittivity): ASTM D4491
• Tensile strength: ASTM D4632 (grab) and D4595 (wide-width)
• Ultraviolet durability: ASTM D4355

In India, guidance from the Central Water Commission, the Ganga Flood Control Commission and the Central Board of Irrigation and Power informs their use on rivers.

Ganga River Stabilization With Geosynthetics: How It All Works Together

The Complete System

Ganga river stabilisation with geosynthetics is a layered system in which each element has its own job:

1. The woven geotextile filter protects the foundation soil.
2. The geotube core provides the heavy, flexible, permeable mass that holds the bank line.
3. The geobag apron guards the toe against scour and lets the structure adjust as the bed changes.
4. Geocells and erosion control mats hold the surface against rain and runoff on slopes above the waterline and let vegetation establish.

The system deforms with the river bed and lets water through instead of standing rigid against the flow, so local scour or settlement does not bring the whole structure down.

Environmental Fit With Namami Gange

Geosynthetic bank protection fits the aims of Namami Gange in several ways:

• It uses locally dredged sand instead of quarried stone, avoiding quarrying, long-distance haulage and the associated carbon
• Geotextile tubes are also a sediment-management tool: the same technology dewaters dredged material and treated sludge
• Stable banks put less silt into the river, which supports the mission’s goal of a cleaner river

Project Case Studies

Sand-filled geosynthetic protection has been used on several of India’s large rivers and coasts.

West Bengal – Ganga Erosion Reaches

On the Ganga in West Bengal, districts such as Malda and Murshidabad have lost land and homes to the shifting river for decades. Sand-filled geotube revetments and geobag aprons can hold the bank line using dredged river sand, and they can be built during the dry working season before the next flood.

Assam – Brahmaputra Dyke Protection

The Brahmaputra in Assam, outside the Ganga basin, is one of the most braided and erosive rivers in the world. Geotextile tubes and geobags have been used there to protect vulnerable dykes and embankments where stone is scarce, which makes it a useful reference for similar works on the Ganga.

Gujarat – Shoreline and Bank Protection

Along the coast and rivers of Gujarat, geotextile tubes have been used for shoreline and bank protection and for reclamation bunds, under very different water conditions from an inland river.

Ocean’s own river protection projects include 9,000 Ocean geobags on the flood-prone banks at Chhapra, Bihar and riverbank protection on a Namami Gange project. More are listed on our case studies page.

Product Specifications at a Glance

The table below summarises the main geosynthetic products used for riverbank protection on a programme like Namami Gange, with their functions and the standards that apply.

The right grade for any location depends on the flow velocity, bank height, scour depth and design life, so each reach needs its own product selection.

Why Ocean Non Wovens for Riverbank Protection Projects

River protection at Namami Gange scale needs materials of consistent quality delivered in volume to difficult riverside sites.

Ocean Non Wovens is an Indian manufacturer and supplier of geotextile tubes, geobags, woven and non-woven geotextiles, geocells, geogrids and HDPE liners, tested to Indian and international specifications.

Ocean Non Wovens supplies materials for:

• Riverbank protection and flood control
• Scour defence and erosion control
• Dewatering and sediment management
• Highways, expressways and defence infrastructure
• Railways, water resources and industrial developments

For engineers and agencies on bank-protection works, that means one source for the geotextile tubes, geobags and filter fabrics a river stabilisation job needs, with technical support to specify the right product for each reach and flow condition.

If your project involves geotextile tubes, geobag riverbank protection, scour defence, filtration or erosion control, talk to Ocean Non Wovens.