Grey Water Research Grey water irrigation testing with popular native plants. By Todd Layt Summary…
Turf in recent research has proven to be one of the best erosion control products, testing far better than silt fences, coir logs and erosion socks for both erosion and silt containment.
Established turf by itself can easily handle 1.5 metres per second flows. Well established turf has been shown to handle flows of 2.5 to 3 metres per second.
The biggest problem with using turf in flow areas is that until establishment, it can shear away. Traditionally this was solved by using turf combined with netting and pegs, or turf secured with wire pegs.
Both netting and wire pegs can be dangerous hazards to foot traffic, 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.
Tests in the USA showed that the 150mm E-Staple took 12 times the force to remove compared to a round top 150mm steel staple, and more than 4 times that of regular 150mm steel staples.
Now that there are such strong biodegradable staples, it was decided to test which would fail first, the staple or the turf.
It was also decided to test what force is require to pull 6 x 150mm and in another test 6 x 100mm staples from the ground, pegged through Nara™ Native Turf and regular Wintergreen Couch turf.
All rolls were of good quality. A bamboo stake was secured to wire, and a weighing device attached. 10 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, 6 pegs were installed, 3 either side of the bamboo bar, with 3 of those being adjacent to the end of the turf roll.
To test the breaking point of Nara™ Native Turf, 12 150mm staples were used, 6 placed either side of the bamboo bar.
After each test the ground was compacted with a spade, and the end of the turf roll was cut off so a new undamaged end was available for testing.
After all testing was complete, the Nara™ Native Turf was installed, and 9 x 150mm staples were places in one roll, and 9 x 100mm staples in the other.
These were tested with 1 metre per second flows for 8 hours, with 2 metre per second flows of water for short durations.
Just below shows the average of 10 tests. Measurements are in Kilograms.
Nara no staples 2.959
Nara 100mm staples 8.358
Nara 150mm staples 29.046
Nara 12 150mm staples 37.747
Couch no staples 2.704
Couch 100mm staples 8.178
Couch 150mm staples 22.181
The 100 mm E-Staples took just over 8 kg to shear them from the ground. No staples broke through or tore through the turf. The turf remained intact.
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 29 KG to shear the 150mm E-Staples from the ground. The staples failed before the Nara™ Native Turf did.
The Wintergreen failed before the staples did. Some of the staples tore through the Wintergreen each time. The average shear of the wintergreen was 22kg.
To test what force would be needed to tear the Nara™ Native Turf, 12 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 NaraTM Native turf were laid in 1 metre per second flows for eight hours, with short 2 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.
Discussion Until recently pegs or staples usually pulled out before the turf broke. Now with the invention 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 stronger turf sod. The implications 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 capability.