Type	Hosted Feature Layer
Update Frequency	Every 10 years
Contact Details	data-request@mhl.nsw.gov.au
Relationship to Themes and Datasets	Water theme
Accuracy	Based on ground truthing. The field trips were planned to coincide with predicted ocean tides higher than 1.80 m ISLW calculated from data recorded at the tide gauge maintained by MHL located at Middle Head in Sydney Harbour. This meant that although a survey may not have been done on the highest predicted tides (approximately 2.00 m ISLW) the difference would be generally not more than 20 cm. The actual difference would be less than this by the time the ocean tide had travelled to the extremities of the estuary. So the threshold of 1.80 m was selected as a compromise between needing to survey the highest tides and having a useful number of tides to work with on any one field trip.
Standards and Specifications	Open, public dataset
Aggregators	DPE Manly Hydraulics Laboratory
Distributors
Dataset Producers and Contributors

For the purpose of this survey a definition of tidal limit had to be adopted and so it was decided that the limit of tidal influence would be the point along the estuary at which the water level no longer responded to the ocean tide. Put simply, the most upstream point at which the water level moved up and down with the tide. This would be the point to which the ocean tidal influence would ultimately penetrate if there was no (or negligible) freshwater flow in the system. After a flood event in a major river it may take one to two months before the freshwater inflow reduced to that of the previous baseflow conditions. In smaller creek systems, after a flood event it may only take one or two weeks for the restoration of the tidal limit.