Tidal interface

Phil Collier & Nathan Daw Quadros

The coastline is defined by the line of intersection between the land-mass and a nominated tidal place. However, the coastline does not have a concise or unambiguous spatial or legal definition, creating uncertainty and potential conflict in the case of competing interests in the tidal zone. This also makes the delimitation of maritime boundaries dependent on the definition of the coastline somewhat problematic. A new approach for defining the coastline that will remove this current ambiguity in the tidal zone will make it feasible to create a single national cadastre covering the both onshore and offshore environments.

In addressing the spatial issues, the research aims to identify and resolve technical issues that impact on the consistent delineation of the coastline. This research uses a technique where by the various tidal datums can be mapped using a mathematical approach. Recent technology which enables coastal terrain data to be captured more accurately at a higher resolution will be supplemented with a harmonic tidal model to derive the required tidal datums.

The research has recently developed a system that produces the height of tidal datums (Highest Astronomical Tide, Mean High Water Springs and Lowest Astronomical Tide) at any given position on the Australian south-eastern coast. This information has been supplemented with foreshore terrain data from NSW to delineate the relevant coastline. The next stage of the project is attempting to calibrate the tide model to improve the definition of tidal lines within bays. This will expand the research into Victoria as the primary focus is Port Phillip Bay.

The importance of this research was recently recognised by the Australasian Hydrographic Society when the research was granted the society's annual education award.