Photo of the Week for 17 March 2002

Damaged bridge in the Coed y Brenin

Flood damage in the Coed y Brenin, Gwynedd

Last summer, at the beginning of July, there was a violent storm in the Dolgellau area of North Wales. Torrential rainfall caused sudden flooding, which badly affected the area. My husband has recently started a Ph.D. with the Arid Zone Studies Department of Bangor University, and this flood event is one of the things he is investigating. Jo, a full-time student on the M.Sc. course at Bangor is also using this flood as the basis for her dissertation.

Having acquired various items of surveying equipment, Graham and Jo set off to measure the river cross sections, which would enable Jo to calculate volumes of water flowing during the flood and to correlate these with the recorded rainfall. My role in this activity was as interested spectator, holder and passer of bits of equipment, occasional recorder of readings and photographer.

One of the most obvious results of the flood was the number of bridges damaged or destroyed. Many of these were old, so must have survived floods in the past. The main photo shows a bridge near the old gold mines at Gwynfynydd, just a little way downstream from the waterfalls. The fallen tree, lying in the river, has come down since the flood, which scoured the river beds clean of vegetation and carried huge tree trunks downstream to pile up against the bridges.

The first site we surveyed was at the base of a bridge that had been completely swept away by the storm run-off. Not only had the span been pushed down, but it had been moved a fair distance downstream.

The end of the road. The arch of the bridge.

Looking downstream, the arch of the bridge can be seen lying in alignment with the natural rock formation.

At the second survey site, Graham discovers that it's not possible to cross the river without getting wet. Graham crosses the river.
Jo using the theodolite. Whilst Jo manages to keep reasonably dry, perched on a rock with the theodolite.

Several local people, out walking in the forest, were curious as to what we were up to. It's just not possible to do surveying work secretly; the long orange and white stripy poles are such a giveaway. They were all interested in the study and one couple, who lived above the washed out bridge, had further information about the night of the flood and the damage caused.

There is more surveying to do, then the calculations, plotting of graphs and the writing up of the findings, but it was certainly a spectacular event and it will be many years before the river beds are covered in moss and vegetation again, as they were before the flood occurred.

The newly scoured river bed.
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