Bridges are an essential part of river landscapes; it is overly simplistic just to say they exist to get from one bank to another. They beg the question, why go there? Why are bridges built where they are?
I think that the answers to those questions are more complex than they first appear and I’m no expert on this (or any other) subject. It is not good enough just to say that they exist to link communities or to provide a through route. Seperate communities spring up either side of bridges and the existence of one is directly due to the other. Where bridges exist for roads or tracks it is relevant to know why the road or track was built in the first place. The building of a bridge is a complex exercise and not undertaken in any age without good reason.
In some case I think the trackway may have preceeded the bridge and that originally it would have forded the river at a shallows. I can see that the construction of a bridge in shallow water has to be easier than where it is deeper. Likewise some bridges are clearly built where rivers narrow and again the ease of build is clear for all to see. Other reasons could include local geology and defensive imperative particularly where bridges have a long history.
There are many bridges on the Aylsham Navigation of varying shapes and sizes but the biggest and busiest is the Horstead to Coltishall bridge carrying, as it does an A road with all the comensurate traffic that designation brings. It is the primary road route to the regions capital in Norwich from North Walsham and an entire stretch of coastline. If the bridge wasn’t there a very long detour would be involved. Imagine then the effects of the flood in 1912 which did wash this bridge away as the photograph below (courtesy of Norfolk County Council) shows.
This photograph, I believe, was taken very soon after the flood as the river hasn’t yet returned to normal flow and it is still attracting spectators on the opposite bank through the bridge. My guess is that this is an inspection party assessing the damage and if I’m right I wonder if they had any inkling that it would take three years to rebuild. It’s destruction caused economic and communication difficulties throughout until it was re-opened.