Bridges Are The Single Point Of Failure On A Long Route

Long routes are usually resilient. A blocked path can be walked around and a closed section skipped. A missing bridge is different, because there is frequently no second option.

Rivers do not offer alternatives

A bridge exists where crossing is otherwise impossible or dangerous. That is the reason it was built, and it means the alternative was already unacceptable.

On a large river the next crossing may be a long way upstream or downstream, and reaching it usually involves roads rather than paths.

The detour therefore changes the character of the walk as well as its length, which is why a bridge closure is reported far more urgently than a path closure.

They fail in the conditions that made them necessary

Footbridges are damaged by floods, and floods happen when the river is at its most impassable. The structure is removed at the moment the crossing matters most.

Debris does much of the damage. Trees and material carried by a spate lodge against the deck and supports, and the accumulated obstruction takes the load of the whole flow.

This is why many upland footbridges are built high above normal water level and are still lost, and why some are designed to be removed for winter.

Replacement is slow for reasons unrelated to construction

A new footbridge in a remote place requires design, consents, funding and materials delivered without vehicle access, frequently by helicopter and in a weather window.

Ownership is often unclear. A bridge on a right of way may be the responsibility of a landowner, a highway authority, a national park or a charity, and establishing which takes time.

Where the structure served a small number of walkers, the case for spending a substantial sum has to be made against other priorities, and some bridges are simply never replaced.

Temporary crossings carry their own risk

After a failure, informal arrangements appear: a fallen tree, a cable, a line of stones. These are unmaintained and unassessed, and they attract people who would not have forded the river.

Route managers generally sign the closure and specify a detour rather than acknowledging the improvised crossing, which walkers frequently interpret as excessive caution.

The reasoning is that an informal crossing is at its most inviting in low water and still present when the river rises, and the second condition is when people attempt it.

Planning should identify them in advance

A route reduced to its structures is a short list, and checking the status of each before departure takes little time compared with discovering a gap on the fourth day.

Path associations and land managers publish closures, and on established long-distance routes this information is generally current because a bridge failure affects everyone using it.