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