SPP-05 Surveys of Water Boundaries

Version 1 - 18/07/2018

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1 Introduction

Surveys of land bounded by water can involve complex legal situations and surveyors need to be aware of the principles involved. Obviously any survey to locate a high water mark boundary must not only adhere to legal principles but such practical considerations as cost limitation factors must also be considered. The practice adopted by some surveyors in the past has been to select a position on the ground, taking due regard of local evidence in the form of debris etc. This approach is a practical one, cost effective and tending to preserve what many believe is the basic intention of such boundaries, i.e. alienated land shall seldom if ever, be subject to inundation, although surveyors would need to comply with the accuracy requirements of the Licensed Surveyors Act 1909 and Regulations (in particular regulation 5 of Licensed Surveyors Regulations 1961).

2  Tidal Waters

The current statutory definition (i.e. LAA) of High Water Mark for tidal waters is the ‘ordinary high water at spring tides’ and it is generally accepted that this is equivalent to the definition of Mean High Water Springs in the Australian National Tide Tables. A recent Queensland case has confirmed this assumption.

It is considered good survey practice to carry out high water mark surveys of tidal waters by using levelling techniques to set out an adopted high water mark contour and relating the survey to a recoverable datum, preferably AHD. Survey performed in this way is usually recoverable and more consistent within itself and with other surveys. The Survey Inspection Team of Landgate can make available to surveyors AHD values of high water mark for any part of the State. These values have been determined from the Australian National Tide Tables and Public Works Department of Western Australia publication 47574- 2, and are accepted by the Inspector of Plans and Surveys as being in accordance with the LAA definition of high water mark for tidal waters.

In situations that require greater accuracy a field survey should be carried out. The field survey should establish an adequate amount of tide data for the specific area from which the horizontal location of mean high water, or any other required datum, at specific points on the shore may be obtained. The Survey Inspection Team can advise on the methods of determining a reduced level of high water mark from observations made.

3  High Water Mark on a Tidal River or Estuary

In a tidal river or estuary the tidal range could be expected to be less than the open sea and the times of high and low tide could be expected to lag behind those of the open sea. Winter flow would make the observation of tide heights less reliable so more cycles would need to be observed. Because tidal phenomena reflect cyclical astronomical conditions, elevations based solely on tidal data are usually permanent and recoverable.

The introduction of non-tidal constituents into the calculation process may compromise the reliability of the datum. The masking of the tidal effect by non-tidal forces such as seiche is an example of this condition. Seiche, which occurs in bays and harbours, is the oscillation of water due to barometric pressure and other non-astronomic forces and should be ignored in determining mean high water mark. Where the tidal influence in a river or stream is minimal and in fact negatived by fresh water run-off, a mean water level elevation should not be used for boundary purposes. This situation would require the use of the ordinary high water mark (ie. non-tidal waters definition) for boundary determination purposes.

The accuracy of these determinations is related to the factors involved. Errors could range from a few centimetres to a few decimetres depending on the care taken and the length of the period of observations.

4  Inland (Non-tidal) Waters

There are significant differences in the legal definitions of high water mark for tidal and non-tidal waters. For non-tidal waters the common law states that the ordinary high water line (mark) is an observable physical mark that can be evidenced by terrestrial vegetation, changes in the soil, surface markings (erosion, shelving and litter) and geological characteristics.

The use of ‘ground evidence’ for locating the position of high water mark is valid if such determinations are based on the principle of ‘the limit of useable land’. In most cases, by this method for non-tidal waters, surveyors have adopted the ‘top of bank’ position as defining the ordinary high water line (mark).

Some surveyors, especially last century, erroneously adopted the top of the ‘high bank’ (ie the bank of the floodplain) as the position of the ordinary high water line. As a result, some surveys have been found to be up to hundreds of metres in error.

Where a parcel extends to the centre thread of an inland watercourse (ad medium filum aquae) the survey should define both banks and the centreline of the watercourse.

5  Survey Method

In the past, survey regulations have required that high water mark surveys be carried out using offsets or insets at regular intervals from a traverse line. The use of radiations to each bend in the water boundary from selected traverse stations is considered a more reliable and efficient method compatible with modern survey equipment including GPS.

6  Doctrine of Accretion and Erosion

The doctrine of accretion and erosion applies to tidal and non-tidal boundaries where the change in the position of the boundary is gradual and imperceptible. Where this situation does not apply, the bank must be defined in the same position as immediately before the change. Generally reclaimed land from tidal waters becomes Unallocated Crown Land and inundated land retains its previous tenure.

7  Title Amendment for Water Boundaries

Where large differences from original are encountered in the position of a water boundary and the change has occurred gradually and imperceptibly, a certificate of title can be amended by an application made under section 170 of the Transfer of Land Act 1893. The application would normally need to be based on a new survey plan (see plan example 42) and the survey should identify the impact of the application on any affected adjoining parcels, including those across a watercourse, if applicable. To meet the requirements of section 77 of the Legal Practitioners Act 1893, a section 170 of the TLA application should be prepared by a ‘certificated practitioner’.

8  Freshwater Bay Surveys

Surveyors should be aware that the Melville Water and Freshwater Bay Road Act, 1912 (the Act) empowered the Surveyor General to ascertain and determine the high water mark at Freshwater Bay and Melville Water (i.e. from Mosman Park to Nedlands) for the purposes of the Act. On approval of the Minister for Works such determination became final and conclusive.

Although the Act was repealed in 1966 a survey of the high water mark at Freshwater Bay (shown on Original Plan 5982) was approved by the Minister for Works in 1955. This determination of the high water mark has fixed the boundary between the Swan River at Freshwater Bay and the land (Freehold and Crown) above high water mark. Unfortunately, the Act provided no specific mechanism as to how the Freehold Titles to the land abutting this section of the river were to be amended. The result today is that a number of Freehold Titles reflect a direct access to the Swan River that is not the true legal position.

The river boundaries of land affected by Original Plan 5982 can be defined with some certainty following a renovation of the survey in 1993 by the Inspecting Surveyors. Surveyors should ensure they have a full search when working in the area.

Surveyors defining any river boundaries affected by the Act but outside Original Plan 5982 should seek advice from the Surveying Inspectors at Landgate.

This page was last updated on: 17 Mar 2020