Spring & neap tides
Tidal range often changes regularly, i.e. every fortnight (14 day period)
Spring tides - times of greater tidal range; coincide with full moon or new moon
- Tidal range during spring tides is usually 20% higher than mean tidal range
Neap tides - times of lower tidal range; coincide with first or third quarter
Tidal range during neap tides is usually 20% lower than the mean tidal range