Flood Mitigation Structures Using Geotube - Case Study

Flooding is gradually becoming a common thing during the rainy season. Each year, the sea level is rising about 3mm as a result of a billion tons of ice melting every year.

This has much to do with global warming and almost every country has contributed in one way or another.

Due to the rise in sea levels globally, coastal erosion has become an underlying issue that needs to be attended to immediately. As floods have caused heavy damage to lives and properties throughout the world, flood mitigation has become critical.

Those living in coastal regions have suffered long enough from the devastating effects of floods, and this is why governments have initiated rapid coastal developments to prevent the exacerbation of erosion hazards.

The use of Geotube can mitigate floods in affected areas which, in turn, saves lives and properties. In this post, we look into a case study and how floods can be mitigated using Geotube.

What is Geotube?

Geotextile tubes or Geotubes for short are long woven polypropylene tubes that are mainly used for flood protection, longshore protection, breakwaters and dams.

During Geotube installation, geotextile sheets (permeable, yet soil-tight) are used to drain excess water from the geotextile tube using various container types.

The tube height is decreased as a result of this drainage and needs to be pumped several times to achieve the desired height.

Oftentimes, these geosynthetic containers are applied as storage ballast, earth dam improvement, filters, scour repair and protection, earth dam improvement, armour, and core for hydraulic structures.

Case Study

Almacen River is a major river in Bataan, the Philippines. It has its headwaters in the Natib Mountain, extending down to Hermosa and exiting through the Orani Channel to Manila Bay.

During the rainy seasons, residents of Hermosa, Dinalupihan, and Orani suffer from yearly flooding along these areas. This is because the Almacen River’s severe siltation is caused by the lahar deposit in the upstream river heading to Mount Pinatubo.

Solutions

To mitigate the adverse effect of terrible floods, the Public Works initiated the use of Geotube. Geotube is a silt depo that can address the problems caused by a flood.

Geotube installation will be laid at the river mount and the 4.0 km river of lahar deposit will be dredged to help deepen the river channel.

The idea is for the dredged space to accommodate a larger volume of water during the rainy season. In turn, this will help address the recurrent issue of severe flooding in the surrounding municipalities of Orani and Hermosa in Bataan, Philippines.

Construction

First, Geotube is furnished and laid with a scouring apron. The geotextile installation is protected with a revetment protection structure that serves as a mass gravity structure.

This primary protective function is resistant to erosion and harsh weather conditions.

Experts fill the Geotube by hydraulically pumping sand slurry via the filling ports.

The fill is in the form of sand/water slurry so that Geotube can allow the flow of fill material.

River water may also be used to create the sand/water slurry which is why during Geotube installation the supply of water is free and abundant at the site.

The Geotube, which is now permeable, allows the excess water to flow through the geotextile skin while sand is retained within the Geotube. The installed Geotube serves as gravity massed building blocks to protect against or prevent erosion along the Almacen River.

Details of The Project

Geotube installation serves as riverbank protection for the Almacen River Improvement project. This allows the usage of dredged material along the river as filling soil for slope protection and river embankment.

The installed Geotube acts as an onsite spoil bank area which implies that the use of offsite materials isn’t needed. Thanks to this dredging project, Almacen River’s waterways have been improved as it diverts floodwaters away from the villagers and their farmlands.

Benefits of Geotube Installation

When compared with traditional methods, Geotube installation offers over 85% less CO2 emission.
It reduces disposal at sea for dredged material.
Geotube reduces fuel transport and consumption of excavated material.
Wastewater is used as a resource.

Final Thoughts

The use of Geotube speeds up the completion of the project. Since Geotube installation is fully mechanical, manpower requirement during installation is reduced.

Moreover, using Geotube technology offers a better environmental alternative and more economical method of breakwater construction.