Geosynthetics

ENTRY DATE: 22.04.2015 | LAST UPDATE: 22.04.2015

CATEGORIES:

  • Coastal Regions
  • Materials and equipment

TECHNOLOGIES MATURITY:

Applicable immediately

Technology Owners:

Manufacturing and designing companies

Needs Address

Measures against erosion, storm surges, flooding, inundation

Adaptation effects

  • Flood control, barrier reinforcement, and erosion management through drainage control
  • Provide protection against damage from waves or currents

Overview and Features

Man-made products, such as geotextiles and geo membranes, used in water separation, diversion, or filtration; land protection; and the reinforcement of existing flood barriers to reduce coastal flooding and erosion in areas with periodic or episodic flooding or slow-moving erosion. Geotextiles are porous fabrics made of synthetic materials that have a very tough texture and are filled with sand or a sand fluid-mixture. They include bags, mattresses and tubes. Geomembranes are nonporous barriers used primarily for containment. 

Cost

  • Cost of purchasing the material
  • Cost less to build and maintain than large scale hard coastal structures

Energy source

Machinery fuel to produce materials, etc.

Ease of maintenance

Geo synthetic sheets need replacing if/when damaged by strong wave forces

Technology performance

  • Geo synthetic wraparound revetments, which are sand slopes that are reinforced by geotextiles, can survive 10,000 to 36,000 waves, depending on the construction design (Recio-Molina and Yasuhara, 2005)
  • Different applications more effective than others e.g. a breakwater constructed from geotextile mattresses or sandbags can offer more lateral stability than one made of geotextile tubes or other geo synthetic products
  • Not strong enough to protect coasts against strong forces such as Tsunamis or extreme storm surges
  • They can alter sediment flow patterns and may adversely affect ecosystems

Considerations

  • Implementation is relatively simple as their use requires relatively low levels of technology
  • Easily damaged by strong waves, causing breakage, exposure of under-layers and hence potential damage to ships propellers
  • Difficult to implement in turbid, turbulent water
  • Coarse boulders or shingle should not be used as core material
  • Rock outcrops can tear and damage geo synthetic sheets

Co-benefit, suitability for developing countries

  • Replacement of geo synthetic layers reduces need to replace under-layers saving in material, material transport and placement costs
  • Lack of affordability and accessibility in developing countries
  • Site-specific conditions and techniques must also be considered

Information Resources

Chu, J., S. W. Yan, and W. Li. 2012. Innovative Methods for Dike Construction: An Overview. Geotextiles and Geomembranes. 30 pp. 35–42. Available at: http://www.sciencedirect.com/science/article/pii/S0266114411000094 [30 November 2014]

Koerner, R. M. 2012. Designing with Geo synthetics. 6th edition. Indianapolis, IN: Xlibris Publishing Co.

Recio-Molina, J. and Yasuhara, K. 2005. Stability of modified geotextile wrap-around revetments (GWR) for coastal protection. Geosynthetics International, 13, No. 1.

USAID, 2014. C-cap takes a 'whole-of-island approach' in Kiribati. C-CAP Newsletter Summer Edition 2014. Available at: https://drive.google.com/file/d/0B6XV438G4yW9ODFGNUwwa3AzODQ/view [08 April 2015]

Yan, S.W. and Chu, J. 2010. Construction of an offshore dike using slurry filled geotextile mats. Geotextiles and Geomembranes 28(5): 422-433