Wednesday, October 6, 2010

Erosion!

Costa Rica is experiencing one of the rainiest years in 40 years. In the last few weeks, there have been road washouts, bridge closures, and landslides all over the country. Many people are currently in shelters because of water or mud damage to their homes.
We’ve been fortunate in that regard. We had some serious erosion, but the house and driveway were not affected at all.



Last Wednesday morning around 6:00, we lost power and phone. We weren’t surprised, since we’d received over 4.8 inches of rain the day before and 5.05 inches the day before that. As you approach our house, on the left side of the driveway the rain was too much for several old trees, whose roots weren’t strong enough to hold, so we lost all the trees. They just slid down the steep hill onto the road below and beyond, taking part of the hill and the power lines with them. There was so much water going down the road, that many of the trees and mud were washed all the way down to the corner into the power pole there.

Sadly, those trees were loaded with orchids, bromeliads, and philodendron. Collie has retrieved a few orchids and paddle ferns. Most of the trees are over another steep embankment and not accessible.


Our engineer, Juan Carlos and Norm walked partway down the public road below us to assess

the damage and come up with a plan to stop further damage on the main area between our driveway and the road below. We were afraid that we’re going to need to build retaining walls and re grade. The mud was so thick in spots that they had to steady each other as they pulled their feet out of the sucking mud!
Thanks to Juan Carlos for the "before photos":


Fortunately, remedial work wasn’t as extensive as we thought it was going to be. We’ve decided on using a bioengineering solution, using vetiver plants instead of walls. Vetiver is a grass like plant that has been used internationally in Africa, Indonesia, Viet Nam, Australia, California and other places to mitigate disastrous situations and to stabilize land for agricultural purposes.




The Vetiver grass can grow to roots 3-4 meters (yards) long in a year. The stems are stiff and erect, therefore the plants can resist dislodgment by strong water currents. Because they trap nutrients, an area of vetiver plantings can also contribute to growth of other volunteer plants. See more here: www.vetiver.org / www.vetivercostarica.com





Mario, our part time gardener and two of his cousins spent a day clearing and re-sloping the area damaged by the slide, getting ready for planting. We hired a backhoe to clear away the mud and debris on the road below.










On Friday we ordered 1300 Vetiver plants which I was able to pickup on Sunday. Monday and Tuesday, Mario and his cousin Wilfreo planted the slope. We have another 500 plants on order that I’ll pick up today. We also have several hundred slips of a similar plant that Mario and his cousin prepared for us.

Those are from their farms and we’ll use them on other areas that are more stable. Because we don’t know if their plant is the same species we are not using it on the landslide area. The difference is in the length of the root system. They are both excellent but one has much longer roots.



The excessive rains are predicted to continue this green season and to also extend through November. That is 2 weeks longer than usual. Today is our fourth day without rain (so far) and the reprieve is a welcome relief for everyone. We received 4 inches on Saturday afternoon after the bank was re-sloped and it didn’t erode any further. The dry days allowed Mario and Wilfreo to put in 10 hour days on Monday and Tuesday. It took those two full days to plant the slope.



The weather has allowed for road clearing across the area and the placement of Bailey bridges across some of the washed out roads. It would be a huge relief for everyone if the predictions for excess rain over the next 2 months prove wrong. In the meantime we are working to anticipate any additional problems.