Welcome to the Land Services GroupLand Services Group
SA Government logo.  Link to Ministers' web site Department for Transport, Energy and Infrastructure - Link to home page

    Home > Publications > Surveying-Drafting Manuals and Guidelines > Cadastral Survey Guidelines



Boundaries present themselves in one of two forms, either as natural or artificial boundaries. Natural boundaries are ambulatory in nature and the doctrine of accretion asserts that they may move in position providing that change is imperceptible in time.

Natural boundaries are those evidenced by naturally occurring phenomena such as the seacoast, inland waters and mountain ranges. The most common natural boundaries dealt with by surveyors in South Australia are defined by the mean high water mark (MHWM), or the centre line or banks of streams. Surveyors also deal with boundaries created parallel to natural boundaries (150 link reserves); such boundaries are generally not ambulatory.

Water boundaries are classified as being either riparian (streams) or littoral (shores, that is lakes or the sea and its inlets). It should be noted that the term riparian is commonly used to include littoral boundaries; unless otherwise specified this section shall do the same.

In South Australia disputes over riparian rights are rare as there is a relatively small proportion of land parcels with natural boundaries, due to the lack of substantial watercourses and fresh water lakes.

See PPG sections 12 and 19 for natural boundary plan requirements.


This section refers to some legislation relevant to the ownership of the seabed and the bed of the River Murray. As there is no specific legislation relating to the surveying of natural boundaries the following common law rulings and discussion has been presented to assist understanding.


a. Mean High Water Mark

A-G v Chambers is the precedent generally adopted for the extent of parcels bounded by tidal waters. This case was to resolve the question of the landward extent of the Crown's right to the seashore. While this judgement confirmed the extent as MHWM (also known as medium high water mark or ordinary high water mark, OHMW) it was somewhat imprecise in defining MHWM. The judgement refers to:

This point of the shore therefore is about four days in every week, i.e., for the most part of the year, reached and covered by the tides. 20

...the average of these medium tides in each quarter of a lunar revolution during the year...

...the line of the medium high tide between the springs and the neaps. All land below that line is more often than not covered at high water, and so may justly be said, in the language of Lord Hale, to be covered by the ordinary flux of the sea. This cannot be said of any land above that line...

Comment on this case has come from the Crown Solicitor (DL 3533/1967):

... misunderstanding has subsequently arisen from the Lord Chancellor's reference to "the medium high tide between the springs and the neaps". The words underlined are descriptive only and are not, in my view, juristically definitive: they could, without changing the meaning of the passage in which they occur, have been omitted. The highwater mark of the ordinary tides, not the average of spring and neap tides, fixes the boundary.

Hallmann (1994, para. 13.40) concludes:

Where lands are bounded by tidal waters, the common law rule is that the boundary is the mean high-water mark, ie. the mean of all high tides including the spring and neap tides taken over a sufficiently long period...

Logically, if the extent of the Crown's right to the seashore is MHWM then any land alienated from the Crown abutting the seashore, unless otherwise described, extends to MHWM. 'Low water mark' is a description of a boundary where it is clearly intended that parcels extend over part of the seashore.

It is quite common to find that the line located for the coast on early surveys of waterfront parcels was some distance inland from MHWM. In many cases this is not attributable to the ambulatory nature of the MHWM. The position located by these surveyors was often a line (sometimes labelled) of edge of vegetation, accumulation of debris, cliff edge or top of bank. Redefinition of the seaward boundary of a coastal parcel inland from MHWM would probably require evidence of intention by the Crown to retain a strip of land between that parcel and MHWM.

b. Tidal Rivers

Halsbury's (1998, para.355-14015) comments:

Where land is described as abutting a tidal …river, it is presumed, as with the seashore, that the mean high water mark constitutes the boundary. The common law distinguishes between tidal …rivers and non-tidal…rivers. Where the river is a tidal…the land forming the bed and channel through which the river runs, the alveus 19, belongs to the Crown up to the mean high water mark.

In the absence of any specific legislative definition, 'tidal waters' means those in which the tide ebbs and flows under the gravitational influence of the sun and the moon.

Hallmann (para. 4.4) clarifies that:

The tides must be in evidence for more than half of each and every year. Waters that do not answer that description, or waters that are only intermittently tidal so at times to be naturally cut off from the sea, are deemed at law to be non-tidal waters...

Anecdotal evidence suggests that prior to the construction of the Murray mouth barrages, salt water at times reached as far up the river as Mannum. Furthermore, it is thought that the river may have been influenced by the ebb and flow of tides as far upstream as Blanchetown.

c. Control of the Sea Bed

Raven v Keane confirms the extent, and status, of the foreshore : 'The foreshore, that part of the seashore between ordinary high-water mark and low-water mark, prima facie belongs to the Crown.'

Under Section 15 of the Harbors and Navigation Act 1993 adjacent land is vested in fee simple in the Minister. Section 4 includes in the definition of adjacent land:

land extending from the low water mark on the seashore to the nearest road or section boundary, or to a distance of 50 metres from high water mark (whichever is the lesser distance)...

Section 18 (4) provides that this land: "...if within the area of a council but not within a harbor - under the care, control and management of the council..."

Land vested in the Minister under Section 15 also includes land underlying the territorial sea adjacent to the State. Under the Seas and Submerged Lands Act 1973 the territorial sea extends seaward for three nautical miles from low water mark, agreed baselines, or from bay closing lines joining the headlands at the mouth of true bays.

In relation to Council boundaries the Crown Solicitor (HB 1059/25) advised that:

...the proper interpretation to be placed upon the words "coast", "seacoast", or "seashore" where they, or any of them, are used, without being defined, to fix the seaward boundary ... of a Municipality or a District Council District, is that the boundary extends to low water mark... [italics added].

In recent times the boundaries of some National Parks have been extended to lowest astronomical tide. Lowest astronomical tide is defined as the lowest height of the surface of the sea which can be predicted to occur under average meteorological conditions and under any combination of astronomical conditions.

Go back to Contents page


An obvious point is expressed by the Manual of the NSW Integrated Survey Grid (1976, para 22.4): 'The determination of the limit of mean high water presents no difficulty when the foreshore is steep. On flat grades and where mangrove swamps exist, great care is necessary.'

Where it is necessary to locate on site the present position of MHWM the following methods should be considered. It is recommended that surveyors utilise the current year's SA Government Tide Tables (available from Service SA , 108 North Terrace Adelaide). These tables provide instructions for tidal predictions. Where additional tidal information is required beyond that in the Tide Tables:

  • consult Australian National Tide Tables 1(ANTT), or
  • seek advice from Flinders Ports Pty Ltd.

The main methods utilise a value which is the average of all the high tides for the local area. This value can be observed at the appropriate time or set out using the relationship between the tide gauge and height control. The two main methods shall be referred to as:

  • observing the water's edge, and
  • setting out the MHWM contour.

The advantage of observing the water's edge is that at appropriate times the MHWM is self evident. A problem with this method is that it is only suitable in calm conditions; at locations where swell waves are less than 0.5m at breaking 2. The method is often capable of use in South Australia because much of the coast in settled areas is protected from swells of this magnitude.

Setting out the MHWM contour overcomes uncertainty involved with breaking waves. However, this method is only practical for those parts of the coast within levelling distance of AHD control or a tide gauge. An additional problem with levelling from AHD control is that the uncertainty of the relationship between the local MHWM and the AHD increases the further one is from a tide gauge.

Due to the problems inherent in these methods it is recommended that wherever possible, a sample point located by one method be checked by the other.

a. Observing the Water's Edge

1. from Tide Tables determine the Standard or Secondary Port adjacent to the area of interest. If not adjacent to a Port some interpolation of predictions at Ports either side will be required.

2. if Secondary Ports are used in step 1, determine the Standard Port3 it is related to.

3. obtain the mean of the high tides4 for the Standard Port. (This has been done in Table 1 by averaging predicted high waters 5.)

4. predict from the Tide Tables the time of day the tide equals this height at the Standard Port 6.

5. if a Secondary Port is used apply the time difference of high water at the Standard Port.

6. locate the edge of the water at this time. Particular note should be taken of the page headed 'Accuracy of Predictions and Weather Effects' in the Tide Tables.

If it is not practical to observe the tide at the predicted time of MHWM, or if the high water on a day does not reach the MHWM plane, then a less direct method can be used:

1 - 3 as above.

4. mark the edge of the water at a convenient time (preferably closer to high water than low water).

5. predict from the tide tables the tide height at the time of observation 7 .

6. adjust the marks at step 4 by levelling up or down the beach the height difference between MHWM and the height determined at step 5 (for Secondary Port predictions this height difference must be adjusted by the Ratio of Rises quoted in the Tide Tables).

For both of these methods it is advisable to observe the edge of water on two days, especially if the first day's weather conditions are abnormal. For verification, or greater accuracy, actual tide readings at the Standard Port should be obtained from Flinders Ports and appropriate adjustments made to the predicted determination of the tidal plane.

Standard Port MHWM above Chart Datum AHD above Chart Datum MHWM above AHD
Cape Jervis 1.10 0.87 0.23
Port Adelaide 2.01 1.45 0.56
Port Giles 1.79 1.54 0.25
Port Lincoln 1.23 0.83 0.40
Port Pirie 2.41 1.93 0.48
Thevenard 1.51 0.99 0.52
Victor Harbor 0.87 0.58 0.29
Wallaroo 1.34 1.14 0.20
Whyalla 2.18 1.70 0.48

Table 1 - MHWM at Standard Ports 8

Note: Values in this table must be used in accordance with the qualifications expressed in this section.

Chart datums for Ports may change in subsequent years. Check the current year's Tide Tables for an indication of such changes. The value for MHWM above AHD will not be affected by changes to chart datum.

b. Setting Out The MHWM Contour

Table 1 shows the AHD value for MHWM for the Standard Ports in South Australia9 .

This method involves levelling from AHD control to set out the appropriate contour value for MHWM. The marking of this contour can then be located in a horizontal direction for cadastral purposes. The following should be carefully considered:

1. Values of AHD for MHWM as distance increases from Ports requires intelligent interpolation (that is, not necessarily linearly) between them to obtain the AHD value for MHWM at the site of interest. Note that this is not always valid because of tidal peculiarities in the Gulfs; it may be necessary to obtain expert advice from Flinders Ports.

2. The Manual of the NSW Integrated Survey Grid (para. 22.5) has the following comment:

This method cannot be used with accuracy in positions within estuaries and streams unless reliable information on tidal gradients is available. Tidal gradients vary with the shape of an estuary and distances from the open sea...

3. It may be possible for surveyors to determine an AHD value for MHWM to a greater precision than that shown in Table 1. Chart datum definitions (height difference to adjacent benchmarks) for Standard Ports are shown to three decimal places in the Tide Tables. It will be necessary, however, to connect the datum benchmark to AHD control as these benchmarks do not necessarily have a published AHD value.

4. For determinations at Secondary Ports (or for the purposes of interpolation using a Secondary Port) a chart datum value of MHWM can be determined using the value at the Standard Port, the Ratio of Rises, and the respective values of MHWS10 . Again the value becomes more uncertain as distance from these Ports increases.

5. This Secondary Port value of MHWM above chart datum can be converted to AHD if Flinders Ports are able to provide a height difference to an adjacent benchmark, which the surveyor can then level to AHD control11.

If working close to a tide gauge (or its datum benchmark) there is an alternative method of setting out the MHWM contour that does not require AHD connections. With a chart datum value of MHWM, obtained as described in a3 or b4 above, level direct from the tide gauge or its datum benchmark. Levelling from the datum benchmark requires the height difference to chart datum (see Tide Tables for Standard Ports or Flinders Ports for Secondary Ports).

c. Other Methods

The methods described above are generally adequate for all cadastral surveys. On rare occasions a more accurate determination of the MHWM plane may be required at a site than is obtainable by these methods. This can be achieved by establishing a temporary tide gauge adjacent to the area of interest and recording and averaging all high water values over an appropriate period.

Surveyors experienced in determining MHWM by methods a and b have noticed that a second seaweed line can sometimes be taken as a useful approximation for MHWM for medium to low energy beaches (that is where storm waves seldom exceed 1m). This method of determining MHWM may be suitable as an alternative to graphical methods.

This seaweed line method is to be avoided if at all possible by surveyors not experienced in determining MHWM by the more objective methods. While it has been known to sometimes give good results, it assumes an arbitrary balance between the stage of the tide, the slope of the beach and the amount of wave set-up and run-up. These vary greatly and the method has no logical support. Because wave run-up can be quite large (commonly over a metre in height), this method can lead to large errors if applied on open coasts.


It is anticipated that there will be an increased requirement for surveys to determine contours for land to be subdivided and to establish heights for coastal development. Developers of coastal land are frequently required by local councils and the Development Assessment Commission to provide this information; this is likely to increase as more development is assessed for safety against extreme tides and the effects of sea level rise.

Where benchmarks are not conveniently located, sea level or seaweed marks have commonly been used as survey datum. However this does not always provide sufficient accuracy; the datum used needs to be sufficiently accurate to enable the development to be assessed. It would be desirable for surveyors to indicate the likely range of error when they use these approximate methods, though this has not been common practice in the past.

Where heights are likely to be critical, the accuracy needs to be at least within 0.1m. This is normally only achievable by levelling from AHD benchmarks.

To avoid the cost of levelling to a distant AHD benchmark this standard may be relaxed where land is well above the likely effects of extreme tides allowing for sea level rise (1.5m or more above the extreme wave swash level, which may be discernible from seaweed or other flotsam, or from local knowledge).

An approximate AHD value for the site may be derived by either of the two following methods. These approximate methods should only be used where the subject land or proposed development is sufficiently elevated to cover the estimated error in the method. Height accuracy from these methods to within 0.3m would be expected, and survey should only be carried out when this is attainable.

a. Height Transfer from the Nearest Tide Gauge

This method is only suitable in calm conditions, at locations where the swell waves are less than 0.5m at breaking, and if the site is within 50km of a tide gauge:

1. establish the height of a new benchmark, at the site, in relation to the sea water level and note the time of day.

2. make the appropriate adjustment for tidal travel (refer to Tide Tables) to the site and obtain from Flinders Ports the actual recorded tide at the adjusted time.

3. level from the tide gauge or its datum benchmark12 to AHD control.

4. deduce the height of the new benchmark at the site.

5. estimate the accuracy limits, taking into account the distance from the gauge, wind and sea conditions and any other factors, and indicate this on the survey drawing, together with notes on the method used.

b. Simultaneous Levelling

If there are no nearby tide gauges, but there is AHD control within 20km of the site of interest, the following method may suffice in some instances. As for the previous method, it requires calm conditions and an absence of any significant swell waves:

1. one party levels from sea water level to AHD control.

2. another party simultaneously levels from sea water level to a new benchmark at the site of interest.

3. assuming sea water level adjacent to the AHD control and the site of interest at the same time is on the same plane, deduce the height of the new benchmark.

4. estimate the accuracy limits and indicate on the survey drawing as in step 5 of method a.

Go back to Contents page


Halsbury's (para.355-14020) describes the extent of riparian ownership:

Where the river is non-tidal and runs through the centre of adjoining land, in the absence of statutory provisions, the boundaries are determined according to the common law rule of ad medium filum aquae, which literally means 'to the centre line of the water'. Under this rule, ownership of a non-tidal river, lake or pool is presumed to be divided between the riparian owners down the middle line of the stream.

The middle line is determined according to the usual position of the banks of the river rather than extraordinary periods where flooding or deluge has occurred. The entire area between the banks, including areas that are left uncovered when the water levels are low, represents the relevant alveus 19in this context.

Halsbury's then clarifies the conditions under which the riverbed is excluded from riparian ownership:

The express description of land as 'abutting' a non-tidal river within a certificate of title or plan, without mention of the ad medium filum rule, will not prevent the application of the rule unless clear and express words indicate that the rule is inapplicable. The ad medium filum aquae rule is presumptive and may be rebutted by proof that title to the centre line of the alveus was not intended to pass pursuant to a Crown grant or a subsequent conveyance of title. However, such proof must be unequivocal in nature and either be:

(1) expressly incorporated into the grantor conveyance of land; or

(2) implied where the circumstances indicate that the transferor of the land intended to retain the relevant area for a particular purpose.

An implied intention to rebut the presumption of land ownership ad medium filum aquae will not arise in the absence of strong supporting evidence.

One of the cases cited by Halsbury's is Lanyon Pty Ltd. v Canberra Washed Sand Pty Ltd wherein the judgement says:

...the law holds that it is the exclusion of that land which must be evidenced by the terms of the grant and not its inclusion, and that if not so evidenced that land will be deemed to have been included in the grant ... no description in words or by plan or by estimation of area is sufficient to rebut the presumption that land abutting on a ... stream carries with it the land ad medium filum merely because the verbal or graphic description describes only the land that abuts on the ... stream without indicating in any way that it includes land underneath that ... stream. [italics added].

In cases where the riverbed is excluded from riparian ownership, what is the limit of the riverbed? One definition comes from the case Kingdon v Hutt River Board:

The Hutt River…has defined banks, but the flow of water between such banks is irregular. During the dry months, and for the greater part of the year, it flows in a small channel considerably to the east of the claimant's land. In wet weather the flow is greatly increased, and seven or eight times in a year during such wet weather the water flows from bank to bank, and this flow of water is called by the witnesses "ordinary freshes." In very wet weather the river is "in flood," and then it overflows its banks.

Where a river has defined banks, but the flow of water between the banks is irregular, being confined to a small channel during the dry months and for the greater part of the year, but greatly increasing during wet weather and extending occasionally, in each year, from bank to bank, whilst in exceptional instances, happening once in every two or three years, when the rainfall has been long continued and of great severity, it overflows the banks, the "bed" of the river (in law) extends from bank to bank. It is not confined to the channel in which the water is for the time being flowing in dry weather, nor does it extend beyond the banks to land over which the water flows in time of flood.

Another definition comes from The State of Alabama v The State of Georgia:

...the bed of the river is that portion of its soil which is alternately covered and left bare, as there may be an increase or diminution in the supply of water, and which is adequate to contain it at its average and mean stage during the entire year, without reference to the extraordinary freshets of the winter or spring, or the extreme droughts of the summer or autumn.

…and in such places on the river where the western bank is not defined, it must be continued up the river on the line of its bed, as that is made by the average and mean stage of the water...

While Alabama refers to the limit of the bed being adequate to contain the river at its mean height, Kingdon's definition of the bed appears to be higher. It includes the banks up to a height beyond which the stream is considered to have overflowed in flood. This height would appear to be the top of the bank that contains the stream in its normal flow

Hallmann concludes (para 13.64, 13.65) that while NSW legislated a definition for the limit of the bed of a river (adapting the definition in Alabama) the Kingdon definition would be applicable for cases not falling within that legislation.

Apparently there was a definable top of bank in Kingdon's case. It may be that Alabama is applicable in the absence of a definable top of bank as it included consideration of stretches of river with low and flat banks where during freshets water spread as far as half a mile beyond the river.

a. Dams

The precedent established by Yeomans v Peter is relevant where a lake bed is excluded from riparian parcels alienated after construction of a dam. Hallmann (para 13.50) summarised the judgement:

...it was held that the boundaries of an artificial lake, as contained by a dam wall, would, in absence of evidence to the contrary, be fixed by the line representing the level of the water when the lake was full to the top of the dam wall.

b. River Murray

Two issues in particular should be considered with respect to exclusion of all or part of the bed of the River Murray from its riparian parcels:

1. Legislation

The Control of Waters Act 1919-1975 stated at Section 5:

Where any watercourse to which this Act applies forms the boundary, or part of the boundary, of any land which after the date of the passing of this Act is alienated by the Crown, the bed and banks of such watercourse shall, notwithstanding such alienation, remain the property of the Crown and shall not pass with the land so alienated, unless the alienation is made pursuance of some agreement existing at the date of such passing and inconsistent with this Section. [italics added].

The Act specifically included application to the River Murray in Section 3 (1) by stating "This Act shall apply to - (a) that portion of the River Murray which is situated between Mannum and the eastern boundary of this State... ." The Control of Waters Act was repealed by the Water Resources Act 1976; the later not having provisions similar to Section 5.

Regulation 13 of the Harbors and Navigation Regulations 1994 specifies that the River Murray upstream of the sea mouth does not vest in the Minister.

2. Weirs & Barrages

Any riparian land alienated (from the Crown) prior to 1940 as far upstream as Blanchetown may be limited to MHWM (see Table 2 and section 12.3b). See section 12.7a for comment on innundation of MHWM.

Structure Date of Completion AHD Elevation
Lower Pool
AHD Elevation
Upper Pool
Barrages 1940 Tidal 0.75
Lock 1 Blanchetown 1922 0.75 3.30
Lock 2 Waikerie 1928 3.30 6.10
Lock 3 Overland Corner 1925 6.10 9.80
Lock 4 Bookpurnong 1929 9.80 13.20
Lock 5 Renmark 1927 13.2 0 16.30
Lock 6 Murtho 1930 16.3 0 19.25

Table 2 - River Murray Pool Levels

The situation for land between the barrages and Blanchetown alienated after 1940 is less certain as damming of a tidal river cuts it off from the ebb and flow of tides.

For parcels upstream of Blanchetown, alienated after construction of river locks and weirs, raising the water level should not logically affect the presumption of ad medium filum aquae. Where, however, the river bed has been excluded from riparian parcels:

  • if the pool level is above the historic banks, the pool level, being the normal river level in the absence of banks, would be the appropriate extent for the limit of the stream bed in accordance with Alabama's case (see section 12.6). This contour may be set out in accordance with Table 2.
  • if the historic banks are not inundated the extent of ownership of riparian parcels would be unaffected by the timing of alienation relative to weir construction.


For the doctrine of accretion (or erosion) to apply two factors must be present:

  • an ambulatory boundary, and
  • a gradual and imperceptible change caused naturally.

When redefining natural boundaries surveyors must assess the evidence collected to determine whether the doctrine of accretion is applicable.

At common law where movement of a natural boundary is not gradual, natural and imperceptible the boundary becomes fixed in the position immediately prior to such movement. The surveyor must compile whatever information is available to ascertain the boundary position at that time.

The natural and imperceptible criteria require particular qualification. Discussion of this and other consequences of accretion and erosion follow.

Unintentional interference with the tidal flow led to the case Brighton and Hove General Gas Co v Hove Bungalows Ltd:

The general law of accretion applies to a gradual and imperceptible accretion to land abutting upon the foreshore brought about by the operations of nature, even though it has been unintentionally assisted by, or would not have taken place without, the erection of groynes for the purpose of protecting the shore from erosion.

The general law of accretion also applies where the natural accretion, gradual and imperceptible, abuts upon land of which the former boundary was well known and readily ascertainable. [italics added]

In the case Verrall v Nott even though the process of accretion had been facilitated by the erection of a rubble wall by Verrall it was held:

That Verrall was entitled to the benefit of any accretion to his land from the sea, although the original boundary of his land was ascertainable.

That Verrall was not prevented from taking the benefit of accretions because of the erection of the rubble wall.

Hallmann (para 13.45) also refers to the above two precedents dealing with actions leading to unintentional accretion and then confirms that:

In other cases, however, where the landowner's acts can be shown to have been intended to cause accretion, the doctrine does not apply: A-G v Chambers (1854); A-G of Southern Nigeria v John Holt & Co. (Liverpool) Ltd (1915).

Southern Centre of Theosophy Inc v State of South Australia confirmed that the doctrine of accretion is applicable to non tidal lakes, and that '...accretion may also occur where the deposits are carried by the wind, if they become settled and extend the boundary of the land into the water...' (Hallmann para 13.44).

This judgement considered the criteria of imperceptibility in some detail. The court accepted that in certain conditions of wind and weather, movement of sand was detectable, however:

Movement of parts of the dunes, or of drifts of sand upon the dunes, is not the same thing as movement of the land boundary out into the sea. The one may be observable but does not, of its nature, constitute the other. The real question is how long it takes for a consolidation to take place bringing about a stable advance of the land.

Eligibility to accretion where the boundary was surveyed as right (straight) lines, also shown as medium high water and a fixed area given, was investigated in 1980 at North Haven. The accretion was due to the Outer Harbor Breakwater. Two international cases supported the claim:

  • State of Penang v Ben Hon Oon. Re Lord Cross:

    It is ... well settled that if the boundary of land conveyed is the line of medium high tide the mere fact that the acreage of the land conveyed is given and that the position of the line of medium high tide at the date of the conveyance can be established - whether or not it is delineated on a plan - will not prevent land which subsequently becomes dry land through the gradual and imperceptible recession of the sea from being added to the land conveyed.

  • Frost v Palmerston North - Kairan a River Board:

    The mere fact that the original boundary has been accurately defined (such as by a reliable survey), and is still definable - will not prevent a land owner from being entitled to an accretion.

Hallmann advises (para 13.38):

Where land in a Crown grant is described as bounded by "measured lines along" the margin of a coastal "lake" (really an inlet) which is tidal, the legal opinion is that the high-water mark is intended to be the boundary, the "measured lines" merely indicating the approximate position of the high-water mark as it was at the date of grant. Such a construction would not apply, however, if the land is described as bounded by " measured lines near" the margin or bank. Presumably, the above constructions would apply to similar descriptions relating to the seashore or to the bank of a tidal stream.

The legal principles involved where a right line, fixed boundary, inland from the coast becomes gradually submerged are somewhat obscure. See Horlin (1994) for discussion of this issue.

Willis (1974, p.14) proposes that the method for apportioning accreted lands to abutting owners depends on the facts of the case. Three methods referred to are:

1. prolonging the side boundaries,

2. joining the previous terminus of the side boundary to the new riparian boundary such that it intersects the new riparian boundary at a right angle, or

3. give to each owner a share of the new shore line in proportion to what was held in the old shore line.

Refer to Willis for a fuller explanation and examples.

a. River Murray - Effect of the Locks and Barrages

The construction of the locks and barrages along the River Murray has complicated boundary redefinitions in the area. The barrages have had a significant effect in the low lying areas around Lakes Alexandrina and Albert. In many instances the intentionally raised river level is above the old limit of the lake or river bed meaning the doctrine of accretion is not applicable and the now fixed boundary is lost. That is, the extent of tidal influence is no longer evident and the historic bank of the river is permanently submerged.

The locks and weirs have caused only minor inundation upstream and may not have raised the river level above the original river bank. If so, the riparian boundary probably remains ambulatory and locatable.

In areas of inundation there are various methods for determining the position of the historical limit of the river bed, either to enable delineation of a lost boundary or to determine if the historic bank is still above water. Some of these methods are outlined below:

1. By Survey

Many of the original surveys of the river located the edge by line and offset. This position may be re-established from a combination of the original surveyors field work and physical evidence of the boundaries.

2. By Vegetation

In a number of areas, particularly in the lower reaches, considerable inundation of lands adjacent to the river has been caused by the construction of the barrages. In some of these areas a line of trees are found at the edge of the historical bank.

3. From Records Held by SA Water

In the years around 1907, the old EWS Department undertook a detailed topographic survey of the River Murray; numerous cross sections were taken. These records contain some information regarding the position of the bank and river both horizontally and vertically and could provide assistance in redefinition of the river banks in some areas. Contact the Dams & Civil Unit of the Engineering Group of SA Water.

4. By Scale and Plot

In cases where no other evidence exists the historic edge of river can be fixed by scaling from the original survey plan.

Go back to Contents page


In 1835, prior to his departure for South Australia, Colonel Light was instructed in all surveys to reserve as public roads all land within a minimum width of the coast, each side of navigable rivers, and around lakes.

Initially most waterfront roads were fixed during survey of abutting Sections with the landward boundary parallel to and 150 (or 100) links from the waterfront. Colonel Light's instructions were not always uniformly applied and many grants were made with waterfrontages, provision of the roads not continuing to the same extent after about 1845.

Whenever the first opportunity arose after 1898 to dispose of parcels by grant or offer for lease, provision was made for a reserve along the coast and River Murray. In most cases the landward boundary of this reserve was not surveyed, but was merely delineated on existing survey records as a broken line. Very few were dedicated as public roads, and eventually became known as the 150 link reserve. They were not reserves in the sense of having been reserved or dedicated under the Crown Lands Act, but were simply areas of Crown land.

In the 1970s concern by the Surveyor-General about the status of the boundary between the 150 link reserve and adjacent land led to a legal opinion that it was necessary in each case to consider the terms of the land grant, or certificate of title, as to the nature of the boundaries so granted 16.

In the majority of cases the reservation of waterfront land operated as an exception to the land granted. Even though the term '150 link reserve' implied an ambulatory inland boundary it was opined that this would be an unusual step, the usual course being the immediate and permanent fixing of boundaries at the date of the exception. Due to the complexity of the matter the Surveyor-General was advised against the issue of a general direction to surveyors.

An example of the reservation by exception is given in the case McGrath v Williams:

The plaintiff claimed to be the owner in fee simple of a piece of land fronting on the north of Shoalhaven River, which is tidal. The land in question was granted by the Crown in 1843 to plaintiff's predecessors in title. The grant was subject to certain reservations, including a reservation of "all land within one hundred feet of high-water mark on the sea coast, and on every creek, harbour and inlet of the sea." The plaintiff sought to bring the land down to high- water mark on the Shoalhaven River, under the Real Property Act, claiming that the hundred feet reservation had been eroded away. The Crown objected to the plaintiff's application on the ground that the reservation in the grant enabled the Crown at any time to take possession of a hundred feet from the existing high-water mark at the time of such taking of possession. Held, that the reservation operated by way of exception from the grant, and that consequently the hundred feet must be measured from high-water mark as at the date of the grant.

Similar relevant cases on reservation by exception are found in Smith v Renwick and A-G v Dixon.

The case of Allen Taylor & Co Ltd v Croll confirmed that the same principle applies with respect to waterfront roads excluded from land grants. The landward boundary is fixed at the time of grant so the road benefits from any accretion.

Accurate determination of the MHWM or river edge is essential to determining the landward boundary of the reserve. This landward boundary was not directly fixed by survey, it was not marked on the ground so that it could be fenced, and it generally cannot be relocated by directly retracing the surveyors measurements, as there are none.

The date of creation of the 150 link reserve may be obtained from withdrawn Hundred Plans located at the Public Search Counter of the LTRO. The date the land was leased from the Crown can be found in the Crown Lease books held by the Registrar-General.

For new or widened reserve requirements see section 8.4.

a. Coastal Reserves

Determining the landward boundary of the coastal reserve can be a difficult task, where there has been natural and imperceptible movement of the MHWM. Often the original survey was carried out some time before delineation of the reserve, which in turn may have been some time prior to alienation/exception. Consequently there is no record of the position of the MHWM at the time of exception of the 150 links.

One method of determining this landward boundary is as follows:

1. plot the high water mark located by the original survey.

2. using one of the methods in section 12.4, determine and plot the position of the present MHWM.

3. from records held in the LTRO, determine the date the land adjacent to the coastal reserve was alienated.

4. determine the position of the MHWM at the time of alienation by proportioning between the original and present determination of the MHWM.

5. set out a line 150 links back from the position derived for the MHWM at step 4 17.

b. River Murray Reserves

Surveys adjacent to the River Murray commenced in the 1840s, initially around Lake Alexandrina. By 1870 most of the Hundreds up to Morgan had been surveyed. Surveys between Morgan and the State border were completed by 1920. The definition of the landward boundary of the 150 link reserve is the main problem facing surveyors re-establishing boundaries adjacent to the River Murray due to the affect on the river of the construction of the weirs and barrages:

  • In some cases the historic edge of the river (see sections 12.6 and 12.6b2) will have been inundated. Parcels alienated prior to the construction should be located 150 links from a point as determined by one of the methods described in section 12.7a.
  • On the other hand, inundation of the historic edge of the river where alienation occurred after construction would be treated differently. Consistent with the principles in Yeomans v Peter (section 12.6a), the landward boundary of the reserve is considered to be 150 links from pool level. This can be measured from a contour set out in accordance with Table 2.
  • The timing of alienation in relation to construction would be irrelevant where the historic edge was the bank 18 and it has not been inundated; the 150 links should be measured from the bank at the time of alienation/exception.


The following list contains information relevant to natural boundary law. While far from exhaustive it does provide a range of reference material. Not all will be specifically relevant to the South Australian system.

Books & Articles

Butt (1995), The Laws of Australia, The Law Book Co.

Brown (1980), Law Relating to Land Boundaries and Surveying, Association of Consulting Surveyors, Queensland.

Hallmann (2nd edition, 1994), Legal Aspects of Boundary Surveying as apply in New South Wales, The Institution of Surveyors, Australia, New South Wales Division.

Halsbury (1998), Laws of Australia.

Horlin (1994), Submerged Boundaries, The Australian Surveyor, Vol.39 pp40- 45.

Manual of the NSW Integrated Survey Grid (1976), NSW Department of Lands.

Moore (1968), Land by the Water, The Australian Law Journal, Vol.41 pp532- 542.

Weidener (1979), Surveying the Tidal Boundary, Surveying and Mapping, Vol.39 pp333-342.

Willis (1974), Notes on Survey Examination, NSW Registrar-General's Department.


Allen Taylor & Co Ltd v Croll (1923) LVR 87

A-G v Chambers (1854) 43 ER 486

A-G v Dixon (1904) 273 AC 277

A-G of Southern Nigeria v John Holt & Co (Liverpool) Ltd (1915) AC 599

Brighton and Hove General Gas Co v Hove Bungalows Ltd (1924) 1 Ch 372

Frost v Palmerston North - Kairan a River Board (1916) NZLR 643

Kingdon v Hutt River Board (1905) 25 NZLR 145

Lanyon Pty Ltd v Canberra Washed Sand Pty Ltd (1966) 115 CLR 342

McGrath v Williams (1912) 12 SR (NSW) 447

Raven v Keane (1920) GLR 168

Smith v Renwick (1882) 3 LR (NSW) 398

Southern Centre of Theosophy Inc v State of South Australia (1982) AC 706

State of Alabama v State of Georgia (1859) 64 US 515

State of Penang v Ben Hon Oon (1971) 3 A11 ER 1163

Verral v Nott (1939) 39 SR (NSW) 89

Yeomans v Peter (1895) 16 NSWR (Eq) 197

Case Reference Abbreviations

AC                English Law Reports, Appeal Cases

CLR              Commonwealth Law Reports

Ch                 Chancery 1891-

ER                 English Reports

GLR              Gazette Law Reports (NZ)

LVR (NSW)  Land & Valuation Reports

LR                 Law Reports

NSWR          NSW Reports 1960-1970

NZLR            New Zealand Law Reports

SR                 State Reports

US            United States Supreme Court Reports Lawyers Edition 1754-1956

1http://www.bom.gov.au/oceanography/tides/MAPS/sa.shtml also has predictions for current week.

2Even after averaging out the water level fluctuations, breaking waves induce a higher still water level inside the breaker zone. This higher still water level will vary with the slope and nature of the coast, but is generally about a tenth of the offshore wave height. On exposed coasts the tide heights at the beach will nearly always be between 0.1m to 0.6m higher than those deduced from nearby tide gauges depending on the prevailing wave height.
Back to Reference

3 See ANTT for additional Secondary Ports. Those possibly useful include Arno Bay, Elliston, Port Neill and Port Stanvac.
Back to Reference

4 Note MHWM is not the same as the average of mean high water springs (MHWS) and mean high water neaps (MHWN) (see section 12.3a). The average of MHWS and MHWN can be significantly different to averaging all the high tides (for example, at Port Adelaide the former is 0.18m lower than the later).
Back to Reference

5 In averaging the predicted high waters for a full year, it is noticed that the average of the high waters for the months closest to the equinoxes (March or September) gives a close approximation to the full year average. Similarly, the average of all the high waters in both of the months closest to the solstices (June and December) is a close approximation.
Back to Reference

6The interpolation between high and low waters is sinusoidal, not linear. This interpolation can be determined from the ‘Table for Finding the Height of Tide at Times between High and Low Water’ in the Tide Tables or the following formula (derived from ANTT):



  • t is the time at which tide is at height h.
  • t1 and h1 denote the time and height of the tide (high or low) immediately preceding the tide height h.
  • t2 and h2 denote the time and height of the tide (high or low) immediately following tide height h.
  • the arc cos function is solved in degrees.

Back to Reference

7 This interpolation can be determined from the ‘Table for Finding the Height of Tide at Times between High and Low Water’ in the Tide Tables or the following formula (derived from ANTT):



  • h is the tide height at time t.
  • t1 and h1 denote the time and height of the tide (high or low) immediately preceding time t.
  • t2 and h2 denote the time and height of the tide (high or low) immediately following time t.
  • the argument for the cos function is in degrees.

Back to Reference

8 In Table 1 MHWM above chart datum has been determined by Land Boundaries Branch from Tide Tables. This was done by averaging all the predicted high waters for the months of March, June, September and December. Cape Jervis's value was determined from 2008 predictions (when chart datum lowered 0.30m), Wallaroo's value was determined from 2005 predictions (chart datum lowered 0.10m). Port Lincoln values were determined from 2004 predictions (chart datum raised 0.20m). Port Adelaide's (Outer Harbor) value was determined from 2001 predictions (chart datum raised 0.27m), Victor Harbor's from 1999, Port Giles's from 1998, and the remainder from 1997.
Back to Reference

9 The values for AHD above chart datum in Table 1 are taken from Tide Tables.
Back to Reference

10MHWMSecondary = MHWSSecondary - RR(MHWSStandard - MHWMStandard)


  • RR = Ratio of Rises (from Tidal Data and Levels table in Tide Tables).
  • MHWMStandard = MHWM above Chart Datum from Table 1.
  • MHWS from Tidal Data and Levels table in Tide Tables.

Back to Reference

11At some Secondary Ports tide gauges no longer exist, however the chart datum benchmark may still be extant.
Back to Reference

12Obtain the height difference from chart datum to the datum benchmark from Tide Tables for Standard Ports or Flinders Ports for Secondary Ports.
Back to Reference


16 In a minority of cases the reservation operates as a defeasance, expressing the grant as being subject to a public right of way 150 links wide adjoining the coast. The grant retains contingency with the sea/river and the right of way is an ambulatory ribbon 150 links wide.
Back to Reference

17An example of this process is seen on DBP 52, Hundred of Carribie.
Back to Reference

18It is assumed historic edges determined as MHWM, above the barrages, have been inundated.
Back to Reference

19Alveus is defined as "the land forming the bed and channel through which a stream ordinarily flows".
Back to Reference

20 May not be applicable to areas such as South Australia that have mixed tides, that is, two high tides per day having marked inequalities in height. A tidal datum based on the higher of these two daily high waters is referred to as mean higher high water.
Back to Reference

Email the Web Administrator
URL: http://www.landservices.sa.gov.au
Last Modified: 13/04/2010 4:40:03 PM
Go To Top Go To Top
Back Top