Native Turf And New Biodegradable Pegs Make A Strong Team For Erosion Control
By Todd Layt
19 November 2013
Turf in new research has demonstrated to be one of the best erosion control products, testing much better than coir logs, silt fences, and erosion socks for both silt containment and erosion control. Established turf grass as a stand-alone can easily handle 1.5 metres per second flows. Well established turf has been shown to handle flows of 2.5 per second. The biggest problem with using turf in flow areas is that until well rooted out, it can shear away. Traditionally this was resolved by using turf combined with plastic netting and pegs, or turf secured with wire pegs. Both netting and wire pegs can be dangerous hazards to foot traffic and animals, and they are both expensive methods. New E-Staple biodegradable pegs, which have been designed to grip into the ground are proving to be far superior, lower cost and safer. Trials in the USA showed that the 150mm E-Staple took 12 times the force to take out compared to a round top 150mm steel peg, and more than 4 times that of regular 150mm steel pegs.
Now that there are such strong biodegradable staples, it was decided to test which would fail first, the staple or the turf. It was furthermore agreed to test what force is require to pull six 150mm and in another test six 100mm staples from the ground, pegged through Nara™ Native Turf and regular Wintergreen Couch turf grass. All rolls were of good quality. A bamboo stake was secured to wire, and a weighing device attached. Ten separate measurements were taken for each test, and the averages calculated. Each end of the roll of turf was weighed without pegs installed. Then for both Nara™ Native Turf and Wintergreen Couch, Six pegs were installed, three either side of the bamboo bar, with three of those being next to the end of the turf grass roll. To test the breaking strain of Nara™ Native Turf, twelve 150mm staples were used, 6 placed either side of the bamboo bar. After each test the soil was compacted with a shovel, and the end of the turf roll was severed and removed so a new undamaged end was accessible for testing. After all testing was complete, the Nara™ Native Turf was installed, and Nine x 150mm staples were placed in one roll, and nine x 100mm staples in the other. These were tested with one metre per second flows for eight hours, with two metre per second flows of water for short durations.
The one hundred mm E-Staples took just over eight Kilograms to shear them from the ground. No staples broke through or tore through the turf. The turf remained unbroken. The staples approximately tripled the force it took to lift the turf from the ground; stapled compared to unstapled. There was no significant difference between the Nara™ Native turf and the Wintergreen Couch.
The results with the 150mm E-Staples was different. The Nara™ turf stayed intact, and took an average of twenty nine KG to shear the 150mm E-Staples from the ground. The staples failed before the Nara™ Native Turf did. The Wintergreen turf failed before the staples did. Some of the staples tore through the Wintergreen each time. The average shear of the wintergreen was twenty two kilograms. To test what force would be needed to tear the Nara™ Native Turf, twelve x 150mm staples were placed around the Bamboo bar on the Nara™. It took on average 37.8 kg to tear the Nara™ native turf. Many of the staples still pulled out, and the Bamboo bar often broke.
Two rolls of Nara™ Native turf were laid in one metre per second flows for eight hours, with two metre per second flows of water for short durations. None of the Nara™ Native Turf washed away, showing that a combination of 150mm E-Staples and Nara™ Native Turf work well in water flow situations.
Until recently pegs or staples usually pulled out before the turf broke. Now with the development of the E-Staple, most types of turf will tear or fail before the staple is sheared from the ground. However, Nara™ Native Turf has a far denser array of stolons and Rhizomes, making it a far sturdier turf sod. The consequences of this are; that with the 150mm E-staples, newly installed Nara™ native turf can withstand far higher velocity water flows than Couch turf before failing. This also has implications for slopes and batters, providing a far stronger initial erosion control ability.