This will be the closest approach to date by an object this large that we know about in advance and an event of this type will not happen again until 2028.
It would not affect the tides or anything else.
If YU55 were to hit Earth, it would exert a force the equivalent of 65,000 atomic bombs and leave a crater 10km wide and 610m deep.
There are concerns of it having an affect on our poles as it gets closer. It was also blanked out on google earth's space viewer so not to concern civilians. For more information there are numerous topics on www.abovetopsecret.com