Potarch

A potarch is a type of river crossing, specifically a submerged bridge typically constructed of timber. These were historically common in Scotland, often used to ford rivers where the current was too strong or the banks too steep for a conventional ford. A potarch is essentially a low-level bridge, built so that the roadway is at or slightly below the normal water level of the river. This means the bridge is often submerged, requiring knowledge of the river depth and hazards to cross safely.

Potarches offered several advantages. They were relatively inexpensive to build, requiring less material and engineering expertise than a high-level bridge. They also presented a lower profile, which was strategically advantageous in times of conflict, as they were less visible and harder to damage. Furthermore, they could withstand flood events better than bridges with high arches, as the water would simply flow over them rather than exerting pressure against the structure.

However, potarches also had significant drawbacks. Their submerged nature made them dangerous, particularly in periods of high water or poor visibility. The roadway was prone to becoming slippery with algae and debris. They also required regular maintenance, as the timber was subject to decay and damage from the river. The use of potarches has largely declined with the advent of modern bridge-building techniques.