Strengthening the Bambolim Dam Project with Ocean Geobags (PET)

For the Bambolim Dam Project in Goa, Ocean Non Wovens supplied and installed 2,000 SQM of Ocean Geobags (PET) to protect the embankment slope against erosion. The bags were filled with local soil and stacked along the slope, forming a flexible, permeable armour layer that holds the embankment through the monsoon.

Project background

Goa is one of India’s smallest states, and its reservoirs and dams supply water for irrigation and local communities. The Bambolim Dam project was taken up to strengthen the embankments, control soil erosion and improve slope stability.

Goa receives around 3,000 mm of rain a year, nearly all of it in the June to September monsoon. Intense rain and fast runoff erode embankment slopes, scour the toe and weaken the soil. Stone pitching and cement blocks are the traditional answer, but they are costly, rigid, and need quarried stone brought to site.

Why geobags

Geobags are bags of high-strength geotextile, filled on site with sand or soil and placed as a revetment. They are widely used for erosion control, slope stabilisation and embankment protection on rivers, coasts and hydraulic structures. In dam embankment work they offer:

• Erosion resistance: The filled bags form a protective layer against flowing water and wave action.
• Flexibility and permeability: The bags move with the embankment as it settles, and water drains through the fabric, so pore pressure does not build up behind them.
• Lower cost and easier logistics: Empty bags are light to transport, and the fill is usually local soil, so far less stone has to be hauled in than for pitching.
• Vegetation: Grass can root into and through non woven bags, which binds the slope further.
• Durability: UV-stabilised PET geobags resist sunlight, abrasion and microbial attack.

What the geobags do at Bambolim

Ocean Non Wovens supplied 2,000 SQM of Ocean Geobags (PET), made to the requirements of the dam embankment.

• Slope protection: Bags filled with locally available soil were placed systematically along the embankment slope to prevent erosion during heavy monsoon inflows.
• Drainage: The permeable fabric lets water flow out of the embankment in a controlled way, preventing excess hydrostatic pressure.
• Settlement: Embankments settle unevenly over time. Unlike rigid concrete, the geobags follow that movement without cracking or dislodging.
• Vegetation base: The geobags give vegetation a stable base, and the roots strengthen the slope against erosion.

After installation

• Erosion: Post-installation monitoring of the embankment showed a 40% reduction in visible erosion and scouring within the first monsoon season.
• Vegetation: Within six months, native grass began to cover the geobag-protected slopes, adding root reinforcement.
• Water supply: The dam supports irrigation for nearby farmland, and the improved slope stability kept supply uninterrupted during peak agricultural seasons for over 600 farming households in Bambolim and neighbouring villages.

Specifications of the Ocean Geobags (PET) used

• Material: High-strength polyester (PET) non woven fabric
• Size: Project-specific, sized for easy soil filling
• UV resistance: UV-stabilised for durability in Goa’s tropical climate
• Tensile strength: Designed for the hydraulic and soil stresses on the slope
• Installation: Soil-filled and stacked layer by layer, with joints staggered so the bags interlock

On geobag revetments generally, the points to check are fill level (bags filled to roughly 70–80% so they can flatten and interlock), closure of every seam or tie, a geotextile filter behind the bags on fine soils so the embankment soil is not washed out through the gaps, and a toe that is keyed in or apron-protected against scour.

Ocean Non Wovens manufactures and supplies geobags and other geosynthetics for dams, reservoirs, riverbanks and coastal works, sized to site conditions. More hydraulic projects are on the case studies page.