It's true, and it is not just a Dutch problem. Basically all major river systems change throughout the centuries: meandering arms evolve and others get cut off; river deltas grow and change shape and of course human activity shapes the landscape (canals, irrigation, drainage of swamps and floodplains etc.). The ancient city of Eridu for example was a coastal city around 5000BC and today lies hundreds of km inland.

I've recently been thinking about this with regards to borders. There are plenty of borders around the world that rely on rivers as a boundary, but river's aren't static, and meanders shift all the time.

Of particular interest to me was the England/Scotland border, as I was visiting the area, and noticing that it doesn't always follow the path of the river Tweed.

When a river is a border, that is by nature always changing, how do countries decide which bit of land/islands are sovereign?

https://twitter.com/Coding2Learn/status/1397595858632388608

It seems like this is adding some vectors on a gridded base map. But OSM has every object in a vector form, also coastlines etc. So I don't think there is a technical reason why coastlines would have to be fixed for a historical map. On the timescale of ages and millennia, rivers in delta planes are also usually not very static.

I live in the Fens in England and noticed the same thing. You can set it back 1000 years and not only is the Fens still drained, there are artificial drainage channels that weren't dug out for another 600 years. It seems an assumption has been made that rivers and coastlines don't change over time but it's so far from true! For me it's one of the most interesting, and scary, things when looking at old maps. Does the data model support changing natural features like rivers and coastlines?

Have a look at https://www.topotijdreis.nl, it’s a fantastic resource on the national and hyperlocal level.