Tides are a mathematical formula based on the position of the moon, sun and planets, adjusted for local conditions and air pressure.
The Broadmeadow is a special case, the tides above the viaduct are up to 3 hours different to those below - the estuary acts almost like a separate sea for much of the time.
http://www.dusac.org/node/12
Malahide
http://easytide.ukho.gov.uk/EasyTide...ictionLength=7
This is for Dublin Bay:
http://www.boards.ie/vbulletin/showp...6&postcount=30