Engineers take pride in the fact that they can direct the great sources of power in Nature. Sometimes Nature throws off these man-made shackles and demonstrates that she has more power than we had previously imagined.
This was the case at Carr Bridge, on the edge of the Cairngorms, where the Highland Railway from Aviemore climbs up over the mountains enroute to Inverness. North of the station the line crosses a small mountain stream that would often run dry.
The Highland Railway's experienced engineers had constructed a substantial 4.6m span stone arch bridge over the burn, with foundations into the hard mountain gravel. The rail level was 10m above the bed of the burn.
On 18th June 1914 a tremendous storm broke out in the hills to the north. An Inverness-bound train left Carr Bridge station at 15:25 running ten minutes late. As the train proceeded slowly up the 1:60 gradient, Driver Ross saw "water coming through the bridge pretty heavy, but nothing to alarm anybody".
The first unusual thing he noticed was the engine swaying when nearly across the bridge. He kept his train going but was brought to a standstill by the automatic brakes. As he jumped down from the locomotive he saw that the fourth carriage had gone down into the burn on the downstream side.
Passengers quickly abandoned the third and fifth carriages as they tilted on the edge of the collapse, but the fourth carriage fell completely into the maelstrom, with the roof and one side torn off by the force of the water. Four passengers escaped, some clambering out of the upturned carriage, however five people lost their lives. When the flood subsided only small sections of the upstream wing walls were left, with 8-tonne sections of masonry found over 200m downstream.
The cause of the accident was clearly the flood waters undermining the foundations of the bridge, but what was revealed by the investigation was the extraordinary nature of the flood that afternoon. Robert McKinnon, a local farmer had never seen a flood like it in 35 years experience.
The burn had never been deeper than 1.5m under the bridge, but that day the water level rose to 6m as it cascaded through the arch. A considerable amount of debris washed down by the storm had built up a dam across the bridge and included the remains of a 1730s road bridge that was previously 800m upstream. The large body of water and debris suddenly released by the collapse of the road bridge could have been the event that triggered the final destruction of the railway bridge.
Lieutenant-Colonel Druitt concluded his report with "the collapse of the bridge was due to no want of attention or care on the part of those responsible for its maintenance, but due to an event that could not have been foreseen and guarded against".
Would our society today have accepted the accident as an unfortunate but unforeseeable event, or would they be looking for someone to blame?