Shoreline erosion is causing millions of dollars’ worth of damage around the world. Many options for shoreline protection exist, including sandbags, groins, jetties, detached breakwaters and wooden bulkheads utilizing a geotextile.
Bulkheads are very similar in design and construction to standard retaining walls. The crucial difference is a bulkhead is surrounded by water on one side. The constant movement of water in and out of the structure creates two serious problems: Washing out of backfill from behind the bulkhead and erosion in front and under the structure.
As such, the construction of a wooden bulkhead requires the use of a geotextile under the rip-rapped area in front of the wall and behind the center match planks creating the wall. The geotextile allows water to weep out the front of the bulkhead while preventing soil fines from migrating along with the water. A geotextile also prevents the erosion caused by wave action from undermining any rip-rap placed in front of the structure.
- Must Address Movement of Water
- Nonwovens for Clays, Coarse Sands & Aggregates
- Woven Filtration for Fine Grained Sands
The type of shoreline soils are crucial to choosing the correct geotextile. Nonwovens are cost-effective options that perform very well with clays, coarse sands and aggregates. Typically, a 4.5 oz./sy. nonwoven (US 120NW) or 6 oz./sy. nonwoven (US 160NW) are good choices for behind the wall. The choice of a nonwoven for under the rip-rap depends on the weight of the rip-rap and the method of placement. Consult our riprap installation guide for more information on this subject.
However, if the bulkhead is placed on a beachfront consisting of fine grained sands, a woven filtration geotextile is the proper fabric to use. Fine grained sands will cause nonwovens and woven separation, stabilization and reinforcement geotextiles to clog. Woven filtration geotextiles are manufactured from monofilament strands and have a unique property known as percent open area (P.O.A.). P.O.A. creates a clear path for the finest sand particles to pass directly through the fabric without getting caught in its matrix and causing it to clog. There are a wide variety of woven monofilaments from which to choose. In most cases, our US 670 or US 230 products are the best options.
If you have questions about which geotextile is correct for your wooden bulkhead, please contact US Fabrics at (800)518-2290.