--- title: "Holding the River Steady: Ocean Double-Twisted Gabions at a Lock-Cum-Bridge in Malappuram, Kerala" date: 2026-09-16 author: "Sales Team" url: https://oceangeosynthetics.com/double-twisted-gabions-at-a-lock-cum-bridge/ --- September 16, 2026 | [Case Studies](https://oceangeosynthetics.com/category/case-studies/), [Gabion Box](https://oceangeosynthetics.com/category/gabions/) # Holding the River Steady: Ocean Double-Twisted Gabions at a Lock-Cum-Bridge in Malappuram, Kerala A lock-cum-bridge at Malappuram in Kerala needed bank protection and scour defence that could stand up to a monsoon-fed river. Ocean Non Wovens supplied 190 units of **Ocean Hexagonal Woven Double-Twisted Gabion** for the works, used for bank protection, retaining and scour defence around the structure. ## Project snapshot A lock-cum-bridge does two jobs at once. It regulates the flow and level of a river and carries road traffic across it, so the structure and the banks around it are permanently exposed to moving water, changing levels and high monsoon flows. At Malappuram, the banks and approaches needed protection that would not crack or be undermined in that environment. ## Why gabions suit river structures Kerala’s rivers are short, steep and fed by an intense monsoon, so they rise quickly and carry a lot of energy. Around a fixed structure like a lock-cum-bridge that energy concentrates: the flow accelerates through the regulated opening, scours the bed at the foundations and attacks the banks immediately upstream and downstream. If the river undermines the toe of a bank or the base of an approach, the structure itself is at risk. The traditional answer was mass concrete or stone masonry. Rigid protection has two weaknesses here. It is largely impermeable, so unless it is well drained it holds water pressure behind it, and it is brittle, so when the river scours the bed at its foot or the ground settles, it cracks. Gabions are flexible, permeable and built from stone, which is why they are a standard choice for river training, bank protection and retaining walls in hilly, high-rainfall regions. ## What a hexagonal double-twisted gabion is A gabion is a box of steel wire mesh, filled on site with hard stone and stacked to form a structure. The Ocean gabions used here are made from **hexagonal woven mesh** in which each pair of wires is twisted around the other twice, a construction known as double-twisting. If a single wire is cut or damaged, the twist stops the mesh from unravelling, so the box keeps its shape and strength. A welded or single-twist mesh does not have this safeguard and can open up at a single break. The wire is heavily coated against corrosion, with zinc or zinc-aluminium galvanising and, for submerged conditions, often an additional **polymer coating**. Filled with sound stone and laced to its neighbours, each gabion becomes a heavy unit, and a wall of them behaves as one flexible gravity mass. In India this mesh is covered by IS 16014, and internationally by EN 10223-3 and ASTM A975. These standards set wire diameter, mesh size, coating mass and tensile requirements. ## Why gabions were chosen over rigid alternatives - **Flexibility:** When the riverbed scours or the foundation settles, the structure deforms and redistributes load instead of cracking. - **Permeability:** Water that seeps into the bank drains out through the stone fill, so the pore pressure that overturns poorly drained rigid walls does not build up. - **Local materials:** Gabions are filled largely with stone sourced near the site, which cuts the cement and reinforcement that would otherwise be hauled in. - **Speed of construction:** They need no formwork or curing and can be assembled and filled by hand, which suits river sites with difficult access and a short dry-season window before the next monsoon. ## Site conditions - High monsoon flows make **velocities around the regulated opening** severe, with a constant risk of bed scour at the toe of the banks and near the abutments. - The banks are often soft and become saturated in the rains, which raises pore-water pressure and makes them prone to slipping. - Water levels swing between full regulation and drawdown, so the banks go through repeated wetting and drying, and a falling river leaves water pressure trapped in the bank. - High rainfall keeps the ground wet for much of the year, so any protection structure must drain freely. - The works had to be completed within the limited dry period. ## How the gabions work on this structure ### Retaining and bank protection As retaining walls, the gabions hold the approach embankments and riverbanks in place with a heavy **gravity mass** that resists the earth pressure behind, with walls built to a batter or in steps. As revetment on the water-facing slopes, they armour the bank against the drag of the current and wave action. ### Scour aprons At the toe and around the abutments, gabion aprons deal with scour. Because a gabion apron is flexible, it settles into a scour hole and keeps covering the bed, where a rigid apron would be undermined and break. ### Drainage, filtration and vegetation The **permeability of the stone fill** relieves the water pressure that builds in a saturated bank, so the structure drains itself through the seasons. Where a gabion retains fine bank soil, a geotextile filter goes behind it to let water through while holding the soil back, so the bank is not washed out through the stone. Over time silt collects in the voids and vegetation establishes on the face, which binds the structure further and blends it into the riverbank. ## Installation and site practice A gabion structure is only as good as its construction. The key steps are: 1. Units arrive folded, then are assembled and laced together with the specified tying wire so adjacent boxes act as one. 2. The foundation is levelled, and a **geotextile filter** is laid where the structure will retain soil. 3. The gabions are filled with hard, well-graded stone larger than the mesh opening, hand-packed at the exposed faces to minimise voids. 4. Internal connecting wires are placed in taller units to stop the stone bulging the faces. 5. Each course is laced to the one below, and walls are stepped or battered as the design requires. The usual causes of a sagging gabion wall are undersized or poorly graded stone, loose lacing and a missing filter layer behind the wall. ## Durability and maintenance The service life of a gabion structure rests on the **wire coating and the stone fill**. Galvanising, plus a polymer coating where specified, protects the wire against corrosion where the units are wet or periodically submerged. The stone fill is inert, and because the structure is flexible and self-draining it avoids the cracking and pressure failures of rigid walls. Maintenance is usually limited to periodic inspection, especially after floods, for damaged wire or displaced stone. Gabions also have a smaller environmental footprint than concrete for this work. They use local stone and no formwork or curing, they keep groundwater moving through the bank, and as silt and plants take hold they green over instead of sealing the riverbank in concrete. Double-twisted mesh is just as useful away from rivers. At a [coal plant project in Singrauli, Madhya Pradesh](https://oceangeosynthetics.com/double-twisted-hexagonal-wire-mesh-coal-plant-singrauli/), Ocean supplied 140 pieces of the same hexagonal wire mesh for gabion and slope protection works on mine-disturbed ground. ## About Ocean Non Wovens **Ocean Non Wovens** supplied 190 double-twisted gabion units for the bank protection, retaining and scour defence works at this lock-cum-bridge. The company is an Indian manufacturer and supplier of gabions, non-woven and woven geotextiles, geocells, geogrids, geobags and HDPE liners, producing to Indian and international specifications. Ocean Non Wovens supplies river training and bank protection, retaining structures, highways and bridges, airports, railways, water resources and environmental engineering, industrial developments and defence infrastructure across India. For gabion works, slope protection, reinforcement, filtration or containment, Ocean Non Wovens can supply the product to suit the site conditions. **Related:** [gabion boxes and mattresses](https://oceangeosynthetics.com/products/gabions/) · [gabion retaining walls for slope protection](https://oceangeosynthetics.com/landslide-mitigation-and-slope-protection-with-gabion-retaining-wall/) · [non-woven geotextile filters](https://oceangeosynthetics.com/products/geotextile-manufacturers/) Get Ocean Geosynthetics in your Google feed[![](https://oceangeosynthetics.com/wp-content/uploads/2026/07/google-g-logo.svg)Add us as a preferred source on Google](https://www.google.com/preferences/source?q=https://oceangeosynthetics.com/) [![How Ocean Non-Wovens Biaxial Geogrid helped ensure the success of a construction project in Bhubaneswar, Odisha](https://oceangeosynthetics.com/wp-content/uploads/2023/07/Ocean-Non-Wovens-Biaxial-Geogrid-300x225.jpeg)](https://oceangeosynthetics.com/biaxial-geogrid-for-construction-project-in-bhubaneswar-odisha/) [Case Studies](https://oceangeosynthetics.com/category/case-studies/) [How Ocean Non-Wovens Biaxial Geogrid helped ensure the success of a construction project in Bhubaneswar, Odisha](https://oceangeosynthetics.com/biaxial-geogrid-for-construction-project-in-bhubaneswar-odisha/) Ocean Non Wovens supplied Biaxial Geogrid for the construction of a new road in Bhubaneswar, Odisha. The soil along the alignment is prone to erosion,… [See More](https://oceangeosynthetics.com/biaxial-geogrid-for-construction-project-in-bhubaneswar-odisha/) [![picture showing geotextile sheet](https://oceangeosynthetics.com/wp-content/uploads/2021/11/Geotextile-300x221.png)](https://oceangeosynthetics.com/what-is-geotextile-sheet/) [Geotextile](https://oceangeosynthetics.com/category/geotextile/), [Insights](https://oceangeosynthetics.com/category/insights/) [Know Everything About Geotextiles](https://oceangeosynthetics.com/what-is-geotextile-sheet/) Geotextiles are permeable fabrics laid in or on soil. In road building they are used mainly for separation and filtration: they stop fine soil migrating… [See More](https://oceangeosynthetics.com/what-is-geotextile-sheet/) [![Workers laying HDPE geomembrane in an excavated pond with thermal power plant cooling towers behind](https://oceangeosynthetics.com/wp-content/uploads/2026/10/ocean-singrauli-thermal-hdpe-photo-300x225.webp)](https://oceangeosynthetics.com/ocean-hdpe-liner-thermal-power-project/) [Case Studies](https://oceangeosynthetics.com/category/case-studies/) [Case Study: Ocean HDPE Liner Installation for Thermal Power Project in Singrauli](https://oceangeosynthetics.com/ocean-hdpe-liner-thermal-power-project/) For a thermal power project in Singrauli, Madhya Pradesh, Ocean Non Wovens supplied and installed 20,000 square metres of Ocean HDPE Liner-100 Micron. 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