Down by the riverside

It takes a special attraction to bring my neighbor Dédé Repellin down to Pont-en-Royans, and get him leaning over the stone parapet and staring down into the Bourne like a run-of-the-mill tourist.

Here's the special attraction:

This huge mobile elevator work platform enabled a couple of workers to install a plastic tarpaulin trough along the stone wall. Repair work will soon start on this section of the wall, and the purpose of the trough is to catch fragments of old stone and mortar instead of letting them drop down onto the vegetation on the banks of the Bourne. In other words, the future stone craftsmen will be able to work cleanly (no doubt from cables hung down over the parapet) without making a mess of the surroundings. Incidentally, the installation of the tarpaulins demonstrates the extent to which environmental issues are handled seriously these days. Not so long ago, workers would have simply let their rubbish fall down into the river.

Specialists in the domain of mobile work platforms (which is not my case) will recognize immediately that the device is not being used here in an orthodox fashion. The telescopic boom is designed to take the platform up in the air to a maximum height of some fifty meters, whereas it's being used here to attain a "negative height" (expression employed by the operator) whose maximum value is merely ten meters.

The French truck-driver operates the platform. The two fellows installing the tarpaulin were Portuguese and Polish, and they didn't appear to speak a word of French.

This stretch of the Bourne appears to be turbulent, but the volume and behavior of the water vary constantly, depending on the recent meteorological conditions up on the Vercors plateau. For the last few days, there has been no rain here, and this is a view of the Bourne this afternoon, taken at approximately the same spot:

Behind the big square rocks in the foreground, the waterfalls have disappeared. So, what is actually happening here as far as the river is concerned? To answer that question, we need to move upstream some fifty meters, to a point just above the patch of white frothy water in the upper right-hand corner of the previous photo. Here's what we find:

As you can see, somebody has built a small primitive dam here. The river is channeled into what looks like a tiny cavern, where it promptly overflows, as shown here:

Normally, the stream of water created by the dam should flow along the channel cut into the cliff, which you can see distinctly in the above photo. The problem is that a big chunk of the stonework has fallen out of this channel, creating a big hole that allows all the water to escape… whence the white frothy stream.

Exceptionally, the other day, when I was taking photos of the mobile platform, there was a huge volume of water in the Bourne. Consequently, some of the water leaving the dam actually got past the hole at the start of the channel. Then, however, it encountered a section of the rock channel where a dozen meters of the stone wall have disappeared, as seen here:

The waterfalls that I photographed the other day were caused by water spilling through this big break in the old channel.

Now, what was the intended purpose of the dam and the stone channel? A century ago, a local engineer built this system in order to canalize part of the flow of the Bourne into a narrow tunnel through the rock. At the point where this falling water rejoined the Bourne, a hundred meters downstream, it drove a turbine to generate electricity for the village of Pont-en-Royans. In the following photo, you can see the rusty remains of the equipment used to regulate the volume of water about to enter the tunnel.

But, because of the damaged channel, no water has entered this tunnel for half a century.

Today, down below the famous dwellings attached to the cliff face, visitors to Pont-en-Royans probably wonder why the ugly red-brick structure in the middle of the following photo is left standing.

This building, located at the exit of the tunnel, housed the turbine and other equipment for the generation and distribution of electricity. As far as I know, it's still full of archaic hardware. Meanwhile, it remains an element of the riverside landscape of Pont-en-Royans, protected automatically by the French national heritage authorities. So, even though the structure is unattractive and has been useless for ages, it's likely to be around for a long time to come.