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Mining the river
Riverwatch

Sunday, 21 June 2009

View from the Rio Tigre
Topic: Mining the river

First day on the Rio Tigre, I am shocked by what has already happened.  Steve picked me up at the airport and we drove along the waterfront (very nicely improved with pretty concrete ballustrades), through town, and out on the highway where major construction is happening. 

Get this - the highway is elevated!  12-20 feet on fill, all the fill coming from the rivers. I think Costa Rica has traditionally taken stuff from the river because it was there for the taking. The concession to take material from public property (riverbed) only costs an application fee and the hassle (in this case) of going through environmental review.

Up here in Dos Brazos the scene is tranquil, but Steve tells me of the devastation from last November's flood.  Riverbanks collapsing and needing to be shored up with more rock. Parts of the river are already channelized.  And the impact upstream within the Reserve?  I am told that the swimming hole I loved below the little waterfall on the upper river is no more - filled in with sediment washed down by the flood.  I hope the recent rains have scooped it out again.

What does this have to do with road constructiion? Removing material on the lower river, increased velocity, increased erosion, more flooding.  A river is a living organism, one part connected to the other, damage in one area effecting the entire stream. Americans are still trying to repair the damage from placer mining in gold rush days. You would hope that Costa Ricans would learn from our worst mistakes instead of needing to make their own!


Posted by riotigre at 4:21 PM EDT | Post Comment | Permalink

Saturday, 13 June 2009

Osa Treasure in Peril
Topic: Mining the river

Costa Rica is justly proud of its splendid system of national parks and protected reserves.  At the edges of this system are some of the most valuable biological treasures on the planet - tracts of primary rainforest and wetlands that protect many species now scarce in other parts of the country like the red-backed squirrel monkey, southern river otter, Baird's tapir, scarlet macaw, and yellow-billed cotinga.  Some of the greatest treasures are found on the Osa Peninsula in the far southern corner of the country, protected we had hoped by environmental laws as well as their remoteness from San Jose.

Yet in the past few months a danger of unprecedented proportions is threatening this beautiful place and all the creatures that depend upon it.  The danger is the opening of Osa streams to sand and gravel mining to obtain materials necessary for road construction.  Yes, everyone enjoys better roads and the materials have to come from somewhere. But the one place where they should never be removed is the beds of natural streams, particularly small fast-moving streams that run through important natural habitat as they do on the Osa. Here is why. 

In-stream mining - the mining of active stream beds - is one of the most destructive forms of mining ever devised.  It has been banned in the U.S. and many other countries because of its IRREVERSIBLE damage to living streams.  A hydrologist friend, Bruce Melton, P.E., describes it vividly:

What in-stream mining does to create such long lived environmental destruction starts with the removal of the existing river geometry. This "geometry" is what geologist refer to as the the shape and course of the river. It includes all of the little meanders and pools and riffles and rocks and bars and bends as well as the stream side vegetation. The in-stream mining (or placer mining), destroys this geometry and replaces it with a relatively flat surface that ends abruptly at the forest or meadow edge.

There are two major things that happen when this occurs. The overall speed of the river increases. This increases the erosion forces of the river and the number of times that erosion events occur per year.  The faster flowing water means that normally small, nondestructive events will now have a greater water speed and will produce more erosion.  This happens virtually every time a good runoff producing storm occurs, simply because the water can flow faster.  The faster flowing water also tends to spread out the rocks and sand and gravel in the river rather than deposit it in bars and riffles. This eliminates the deep holes and slow moving areas, which means that all of the creatures that rely on the deeper water to survive no longer have homes. The greater erosive force of the altered riverbed creates more erosion along the outside of bends in the river, and increases the rate that the river meanders, or moves around within the riverbed. This has an overall effect of increasing the sideways erosion of the river even more.

This increased erosion leads to the second important part of the destructiveness of in-stream mining. This is the loss of the riparian, or streamside environment.  This piece of the river ecosystem is extremely important to the river as a form of unique habitat that bridges the land and water. It is made up of species that generally only exist along the riverbank. These species not only provide unique vegetation and fruits for the environment, but have roots highly adapted to holding the riverbank in place against the erosive forces of the river. If the in-stream mining does not directly remove this streamside vegetation, the increased erosive force of the mined river will.  When the vegetation is lost, not only are the homes of the animals that require this unique vegetation lost, but the big holes under cutbanks that are protected by massive armor or overhanging roots are lost. All of this vegetation loss means more sun now hits the river. This completely changes the aquatic environment to one that is brighter (predators can see better) and warmer (many species can not tolerate greater warmth, which also does not allow the absorption of as much oxygen as does cooler water for the aquatic creatures to "breath".

 

This is the fate that is in store for the beautiful Rio Tigre river with no less than five commercial companies submitting applications for mining nearly the entire stretch of river between the Golfo Dulce Reserve and the coastal highway.  That's why we have launched an effort to Save the Rio Tigre.  Read more and find out how you can help on our website: http://riotigre.tripod.com.

 

 


Posted by riotigre at 7:41 PM EDT | Post Comment | Permalink
Updated: Sunday, 14 June 2009 11:56 AM EDT

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