We just sold a period house that was both on a fairly busy (rural) A road and had a river at the end of the garden.
Having lived there three years - during which time we fully restored it from total unmortgageable wreck to dream home - we found the road noise was getting progressively worse and despite fitting DG with acoustic glass and spending way too much on a high-end spec we couldn't tolerate it any longer!
One of our main priorities when buying this house was no A roads!
The price was low when we purchased, but that was to compensate for the condition as well as location in proximity to the road. When selling we knew our target market would be smaller and the price we could achieve would be considerably less than if it was in a quieter village. That's something to consider if you don't intend to stay forever - or if, like us, you have a change of heart and need/want to sell quickly.
We found a buyer within five weeks, but had priced realistically and got asking price.
As for the river, it's all relative - ours was a very long way from the house (150'?) and the house was on much higher ground. There was no historic flooding and certainly nothing during our ownership and this caused no issues for our buyer/their lender. Obviously if the river was adjacent to the property this might be a different story!
It's really hard when you're looking for the forever home and yet what you've found has certain drawbacks - I know, we've made a compromise too far ourselves in the past - but imho, if you're that uncertain it may not be the one for you......