Why would you think that medieval people would build such impractical bridges?
After all, there are surviving medieval bridges, which are perfectly capable to allow river traffic.
Stone Bridge in Regensburg, Germany from the 12th century
Edit: the OP is interested in non-navigable bridges.
There is consensus in the comments, that in terms of economy a ...
I will try to explain the complexity of this question using the Duchy of Normandy as an example.
Duchy of Normandy
As reported by Wikipedia in the Duke of Normandy page the duchy arose out of a grant of land to the Viking leader Rollo by the French king Charles III in 911. with the Treaty of Saint-Clair-sur-Epte. Rollo receive the duchy in exchange for his ...
Neither in the Anne Boleyn - Wikipedia account or any other account that I have read has contained the name of the executioner.
William Kingston, the Constable of the Tower, in his writings didn't use the name of the executioner.
Henry commuted Anne's sentence from burning to beheading, and rather than have a queen beheaded with the common axe, he ...
So the question is limited to Middle Age England.
The various kingdoms in Anglo Saxon England were gradually united over several centuries, with the more or less official date of foundation of the Kingdom of England being 927. A few centuries earlier was the period of what is called the Heptarchy.
The name Heptarchy implies there ere seven Anglo-Saxon ...
There was a difference between the hierarchy of ranks and the hierarchy of feudal positions.
The hierarchy of ranks might go from landless knight or man of arms to lord of a manor to count to duke to king.
The hierarchy of feudal positions might go from a fief holder who had no vassals of his own to his immediate superior overlord to his overlord's lord ...
The Wikipedia article on the Buyid dynasty is clear about the fact that the Buyids conquered the Abbasids and made them into a vassal state. So they did not "emerge as allies", but rather as ememies.
At the same time however, the Buyid did depend on the Abbasid to rule, particularly in Baghdad. Here is a relevant footnote from an article which spells that ...
The old London Bridge (1209-1831) not only had arches wide enough for river traffic, it had a lifting drawbridge in the middle to allow tall ships to pass through it. It’s true, however, that the current through the arches was very rapid because of the obstruction to the river from the bridge’s structure.