One problem Kohaku is that all rivers are basically streams or creeks rather then anything one would call a river. So people arn't really going to brand it an outright bug since by all means a small bridge to get into a single nondescript house happens in reality.
Also because of how the game handles resources... the roof of the shack they call a house costs more then the bridge.
The river is 16 dwarf-squares across at that point, by actual measurement. If we use 2m per dwarf-square [1], that's a 32m river, and usually you'd need a few meters past the actual water's edge on either side for support, approaches, etc. For comparison, this is pretty close to the size of bridge you'd need to cross an 8-lane highway in the US (Euro lanes are frequently narrower, it might be closer to 10 lanes there). Depending on depth and flow rate, that's reasonable to call a river (rather than stream, creek, etc.). Prior to 1400, that would *not* have been a casual sort of construction; even now, this is not usually the sort of thing a few people throw up for the heck of it.
With only a quick look, the closest match I found was where the
Aar river (one of the major rivers that make up the Rhine) passes through
Bern, Switzerland. The
Old City of Bern (a UNESCO World Heritage site, with an unusually large amount of the medieval character preserved) had about 5,000 inhabitants, and was situated on a hilly peninsula created by a large loop of the Aar. The
1638 map is obviously later than our target pre-1400 (and the outer defensive works by then had cannon in mind), but you can clearly see the gaps left as the city built successive walls further out. The largely wooden houses were ravaged by a great fire in 1405, and rebuilt in stone afterward; so much of the surviving old city dates from just a hair after the end of our target timeframe.
The
Untertorbrücke has a fascinating history in its own right. Bern was founded around 1191, and their first attempt at setting up a bridge around 1254 triggered a war!
This 1470 manuscript illustration of the 1254 interdiction is an interesting resource. Things were resolved, and the wooden bridge completed by 1256; it survived a heavy siege in 1288. Construction was of oak and at least partially covered.
A 1460 flood severely damaged the bridge, and it was decided to rebuild in stone and a master architect was brought in; construction of the main way was finished by around 1467 when the bridge chapel was consecrated, but further work was put on hold due to cost overruns and various wars.
This 1477 manuscript illustration shows it in the usable but not fully defensible state it was in the interim. Construction resumed in 1484 and by 1487 it was considered complete. Further fortifications were added around 1517, and the state of the bridge around 1600 is visible on
this detailed map drawing. By 1757, the defensive value of the fortifications had become less useful and more of a hassle, and the renovation of the bridge basically consisted of removing the previous defenses, and putting it back much closer to its medieval core.
Note that this bridge remained the only bridge over the Aar in the city until 1834, and the wooden bridge added at that time was a much smaller footbridge. (There was a 1466 wooden bridge built elsewhere to replace a ferry, but that was well outside the city of the time.) Even this
1819 lithograph (from the viewpoint of the far bank) shows that the densely packed medieval city still contrasts with the more pastoral setting on the far bank; and this remains somewhat the case even today;
this high-res 2007 image (click through for much higher resolution version) and
this similar hi-res photo also from 2007 show the difference clearly.
The modern bridge length is listed as 52.5m, with two 14m arches and a 15m arch. Based on Google Earth measurements, the actual water distance, not counting the solid approaches, is about 43-45m. Given the uncertainty on the "actual" size of a dwarf square, this is of roughly equivalent size to the bridges we're talking about, probably about a third longer.
[1] Depending on debate, a dwarf-square is probably between 3' (~0.9m) and 20' (~6m) across, and typically assumed to be on the lower end of that range; I personally tend to think something in the 5' (~1.5m) to 2m (~6.5') range is the best fit, and normally use 2m for simplicity.