The Japanese public works company Taisei has developed an innovative process to revegetate slopes that are susceptible to landslides during rains. The use of old tatami mats both maintains the terrain while vegetation is first developing, and reduces pollution caused from the incineration of tatami mats used to cover the floor of most Nippon homes.

Plants, the best allies of slopes, help prevent rains from leaching the soil. Their roots hold the soil and stabilize it.  Unstable slopes are often the scene of mudslides and dramatic landslides, especially if located near roads and houses.

In the Japanese tradition, tatami mats are made from woven rice straw. The method proposed by Taisei is to cut and enclose the tatami in linen bags of one square meter. The cushions created are arranged in a diamond shape along the slope, allowing the rainwater to drain. Trees can then be planted in the spaces created between the cushions. After five years, when the trees’ roots are strong enough to hold water, the bags will degrade naturally, without outside intervention. This technique would reduce investment 40% compared to the conventional method.

Tatami mats, cheaper and greener

The conventional method, the most popular at present in Japan, usually uses a mixture of plant seeds and mud injected into the ground. A stainless steel mesh is then applied to hold the mixture in place against the rain and protect seedlings against the elements. The technique is particularly expensive because of the use of pumps to plant the mixture. In addition, seeds, imported, could be detrimental to the maintenance of local biodiversity.

Taisei has already tested their new method on a baseball field and will continue their research on different soil types and perhaps use it during their own civil engineering projects.

Credits : Hugues Chataing Bulletins électroniques / Taisei

Translated by Genny Cortinovis

Related content : Japan, revegetation, tatami