Case Study: River & Flood Protection Project in West Bengal Using Ocean HDPE Liner – 750 Micron

West Bengal’s dense river network and heavy monsoon rainfall make it one of India’s most flood-prone states. For a riverbank stabilization and flood protection project in a high-risk river zone in rural West Bengal, Ocean Non Wovens supplied and installed 7,800 SQM of Ocean HDPE Liner, 750 Micron, chosen to resist hydraulic pressure and soil erosion.

Implementation highlights

Location: A flood-vulnerable river zone in rural West Bengal
Total Area Covered: 7,800 SQM
Product Supplied & Installed: Ocean HDPE Liner, 750 Micron
Installation Partner: Ocean Non Wovens technical field team
Project Duration: 21 working days

The problem on site

Sandbags, stone pitching and concrete blocks are the usual flood defences, but they are labour-intensive, and loose or rigid units are displaced or undermined by scour. On this stretch the project team faced:

• Continuous erosion during monsoon surges
• Riverbed scouring and land degradation
• Seepage weakening the embankment foundations
• Risk to nearby infrastructure and farmland

The embankment needed a flexible, impermeable layer that could follow the bank profile and cut off seepage through it.

Why Ocean HDPE Liner, 750 Micron

Ocean HDPE Liner, 750 Micron is a 0.75 mm high-density polyethylene geomembrane used for riverbank lining, flood barriers and hydraulic containment.

• Tensile strength: withstands water flow and mechanical stress during placement and service.
• Chemical resistance: unaffected by saline, acidic or polluted river water.
• UV resistance: carbon-black stabilised for exposed riverbank conditions.
• Low permeability: blocks seepage through the embankment, which removes the water pressure that drives internal erosion (piping).

How it was installed

1. Site preparation: surface levelling, debris removal and compaction.
2. Base layer: a protective geotextile was laid under the HDPE liner to prevent punctures from sharp aggregate.
3. Liner deployment: rolls were laid out with machinery and the seams heat-welded by extrusion welding.
4. Anchor trenches: liner edges were anchored in trapezoidal trenches to resist uplift and movement during floods.
5. Inspection and testing: vacuum-box testing, spark testing and visual inspection checked 100% of the seams.

Vacuum-box testing (ASTM D5641) draws a vacuum over a soaped seam and looks for bubbles; spark testing detects holes in extrusion welds made over an embedded conductive wire. Both are standard for extrusion seams, which have no air channel for pressure testing.

Results and long-term benefits

• Reduced erosion: soil loss and bank recession dropped after installation.
• Controlled seepage: lower seepage through the embankment reduces the risk of embankment failure.
• Land retention: farmland and infrastructure within the flood zone are protected.
• Lower maintenance: fewer repeat repairs than loose or rigid defences.

Details that affect long-term performance

• Cushion and slope design: a geotextile under the liner and a controlled slope reduce puncture and sliding risk.
• Welded seams: fused seams, tested along their full length, are as watertight as the sheet; simple overlaps without welding are not.
• Edge treatment: where possible, Ocean’s team uses bio-engineered turf reinforcement at the edges to combine civil and vegetative flood defences.

Ocean Non Wovens manufactures and supplies geosynthetics including HDPE liners, geotextiles, geocells and drainage composites for flood and river protection, with technical support, quality assurance and installation guidance for government agencies, contractors and private developers. Read more on flood control projects with geotextiles and geotubes, or contact Ocean Non Wovens to discuss your project.