Maybe not in Belgium, but I know there are people panning in other parts of Western Europe. You can find gold, it just may have been worked already..
BBC NEWS | UK | England | Staffordshire | Huge Anglo-Saxon gold hoard found
You don't need a raging river, a lot of guys use streams and I know Europe has plenty of those.
If you ever make it out this way, I'd be happy to take you for a day or two.
That's something that we don't have, since our history is rather young. People can detect stuff from the Revolutionary and Civil wars, but out here in the West, you only find things from the 1800's.... I don't think there is much Spanish Conquistador stuff to be found out here, maybe some ship wrecks.
I have been lurking on a gold hunting forum and there are a number of guys that go to the same area that I am. There is one guy that found at least a gram in a day. In the SoCal, area, the gold is a lot finer. You can find larger nuggets up to an ounce in NorCal. They aren't talking about where they are finding this color, but it's near where I am looking. Now that the river is slowing down, it is easier to cross. They keep referring to river crossings... I need to get up there on a day they are there and see if I can introduce myself, find an in...