There are plenty of visitor moorings in York, most of them marked as 48 hours. Favoured ones are alongside Museum Gardens on the right after you have gone upstream under Lendal Bridge. There are other moorings at King's Staithe and Queen's Staithe either side of the river before Ouse Bridge. There are however no flood safe moorings available for visitors, they are all occupied by the trip boats. If a flood is likely (keep an eye on the weather 30 or 40 miles away in the Dales) you'll need to run away downstream to Naburn Lock or upstream to Linton Lock (quite a long way). There is a water point near Lendle Bridge but it is where the trip boats pick up passengers all day long so you can only use it early in the morning or after the boats stop in the evening.