I received an email from Yoann Copin in Madagascar who is working with a large mining operation. He would like to know if anyone has had experience stopping/slowing soil erosion using either lawn grasses or bamboo. I would like to ask the network, and your newsletter, read by a large number of people with experience in erosion control, might be able to provide an answer.
The following is his statement:
“The mining operation in question will be the largest in the world to date. It will displace a huge amount of soil to reach an important mineral deposit. The consortium will excavate the soil that contains the mineral, mix it with water and slosh the sludge through a huge to be constructed duct down from the mid-plateau region of Madagascar to the East coastal (160 km) port of Tomasina where the slurry will be separated; the extracted mineral hauled off to other countries, while billions of tons of slurry will be spread about in nearby mountain range. So much for the environmental impact! The same company a year or so ago asked a guy to put in vetiver on a newly bared slope to prevent erosion. Unfortunately, the person was inexperienced and did the Vetiver Network a huge disfavor. The job was poorly executed; spacing too large and many of the plants died or were washed away. As the project is getting on and the company is scrambling for solutions, they don’t want to hear about vetiver, claiming it does not work and have closed the door. They have hired a large firm that has convinced them to use lawn grasses and bamboo. Our Vetiver Network guy who was working on a very successful vetiver application for mining project in the South of the country (http://www.vetiver.org/Graphics_Images/MAD-sandunetxt.pdf) when the call for tender was issued, and only found about the catastrophic application after it had failed) needs to find proof that compared with the Vetiver System, specialized lawn grasses (one variety must be from South Africa) and bamboo, which are “known and proven plants” can’t do the heavy soil retention that vetiver can.
What we are looking for is any research, experiences and testimonies of applications of any lawn grass or bamboo to stop/slow soil erosion.”
Criss Juliard, The Vetiver Network (International), Morocco.
The same mistake was made in Thailand. I have seen a lot of plots in which vetiver slips were planted too far apart and not in contour line. As a result the soil was washed away when it rained. You were right, these people have done a lot of damage to the Vetiver Network. As for bamboo, its root to shoot ratio is so wide that the root cannot support the weight of the above-ground part and most likely blown down by strong wind, especially when the soil is soggy wet after heavy rains. This has happened in Thailand when a depression that brought heavy rains to fall to the steep slopes where bamboos were growing,
ReplyDeleteNarong Chomchalow
I don’t have any research proving that lawn grass is not useful for soil conservation, only obvious anecdotal evidence in the fact that I would not use it as it has a root system extending only a few centimetres into the soil which is not capable of withstanding the effects of runoff or being buried under silt. Apart from that there is plenty of research showing that the variety of lawn grasses can’t withstand silt inundation, droughts, fire, wind, grazing or differing soil conditions. Bamboo has shallow roots and can be washed right out of the ground by extreme runoff. Bamboo is the worst possible plant to protect river banks as it can be easily washed out in a flood, transported down river as a massive clump to wash up against even large bridges, forming a “Beaver Dam” capable of destroying the whole structure.
ReplyDeleteWith ‘grass’ being used to control erosion Paul Truong knows how ineffective the strip cropping was in the Darling Downs, as opposed to the vetiver hedges. On the Big Island of Hawaii, I was faced with a problem of handling the enormous sediment output from the Hutchinson’s Sugar Mill in Punalu flowing over our ranch on its way to the sea. This was soil washed from the roots of the sugarcane after it had been mechanically harvested. Usually, in Hawaii, this ‘effluent’ was dumped into the sea but it left such a signature that it could be detected from satellite imagery. As we were not allowed to introduce vetiver grass into Hawaii then, we diverted the runoff into absorption banks that built up terraces. This was very successful - so successful that Hutchinson’s Sugar Mill wanted to charge us for their soil. Vetiver hedges would have been ideal for this job, and will be in Madagascar. One of the major benefits of VS is that you can run the hedges for kilometres without fear of them ‘overtopping’ or bursting. Constructed banks, which do not filter runoff, but accumulate it, have a limit of about 300 m before necessitating spillage in to a drainage outlet. So you would need a lot of constructed banks to be safely effective, also when the constructed banks have filled with silt, they would have to be built ‘higher’, a vetiver hedge would do that ‘automatically’.
Surely in Madagascar there is enough evidence that VS works, couldn’t the mining people be taken there and shown the results?
John Greenfield
Board of Directors, The Vetiver Network International, New Zealand
<27@xtra.co.nz>
You can contact Roberto Neumann, http://www.inta.gov.ar/salta/contactos/cv/Neumann.htm
ReplyDeleteHe is on the VTN and has extensive experience with bamboo.