Ground movement

Guidance on meeting the requirements for cadastral survey datasets (CSDs) that are being prepared under the Cadastral Survey Rules 2021 (CSR 2021) to redefine parcel boundaries affected by ground movement.

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Overview

There are areas throughout New Zealand where ground movement has had an effect on cadastral boundaries both in the horizontal and vertical sense. The movement can be classified as either shallow surface movement or distortion resulting from deep seated seismic rupture. Shallow surface movement generally presents in the form of slow down- slope surface flow, rapid land slip or earthquake-induced liquefaction. Fault zone movement occurs when the bedrock is deformed along a fault line. The resulting ground deformation can present as surface shear or lateral distortion at ground level and as relatively uniform block shift.

The Canterbury Property Boundaries and Related Matters Act 2016 (CPB Act) was enacted to deal with boundary movement resulting from the Canterbury earthquake sequence, 2010 to 2022. This act stipulates that all boundaries within greater Christchurch are deemed to have moved with the movement of land caused by the Canterbury earthquakes, unless that movement was a landslip. The provisions of the CPB Act are only applicable within the greater Christchurch area and not to the rest of New Zealand. Consequently, some rules only apply in greater Christchurch.

For more information see Re-establishing Canterbury earthquake affected boundaries in greater Christchurch

The requirements for dealing with boundaries where ground movement has distorted the land in excess of the relevant accuracy tolerances are set out in Part 8 CSR 2021.

Primary parcel boundaries being re-established and identified as affected by ground movement are dealt with in rule 109. This requires that those boundaries must be defined by survey and ground marked, if practicable, unless they can be accepted under rule 15, (r 109(1)). Further aspects of rule 109 are discussed in subsequent paragraphs.

Requirements for non-primary parcel boundaries on affected land are dealt with in rule 110.

Specific CSD requirements for redefinition of affected underlying parcel boundaries in greater Christchurch are contained in rule 111.

See Re-establishing Canterbury earthquake affected boundaries in greater Christchurch

Key terms

Affected boundary – means a boundary where ground movement has distorted the land in excess of the relevant accuracy tolerances of the CSR 2021 and that has not been subsequently defined by survey and recorded in an approved CSD (r 108).

Canterbury earthquakes – defined under section 4 of the CPB Act as meaning any earthquake in Canterbury in the period starting on 4 September 2010 and ending on 13 February 2022, and includes any aftershock in that period.
Section 4 of the CPB Act

Canterbury earthquake movement – means the movement of land caused by the Canterbury earthquakes (whether the movement was horizontal or vertical, or both), unless the movement was a landslip, as defined under section 8(2) of the CPB Act (r 108).
Section 8(2) of the CPB Act

Earthquake – the shaking and possible deformation of the earth’s surface resulting from the sudden release of locked parts along a fault line.

Disturbed survey mark – means an old survey mark that is in a different position from where it was originally placed, but does not include a change of position due to Canterbury earthquake movement or fault zone movement (schedule 2 CSR 2021).

Fault zone movement – means movement on a fault caused by the deformation of bedrock (r 108).

Greater Christchurch – defined under section 4 of the CPB Act as the districts of the Christchurch City Council, the Selwyn District Council and the Waimakariri District Council.
Section 4 of the CPB Act

Ground movement – means both deep-seated movement and/or shallow surface movement resulting from a natural event including landslip, earthquake, slumping, or surface flow.

Landslip – defined under section 4 of the CPB Act as the movement in greater Christchurch by way of falling, sliding, or flowing of materials that - (a) formed an integral part of the ground before the movement; but (b) had become loose material after the movement (other than by liquefaction).
Section 4 of the CPB Act

Lateral spreading – lateral spreading refers to landslides of saturated soil deposits that have a fluid-like flow down gentle slopes. These can be triggered by earthquake-induced liquefaction.

Liquefaction – earthquake liquefaction is the process by which saturated, unconsolidated soil sediment near the surface is converted into a suspension during strong and prolonged earthquake shaking. The effect on structures and buildings can be devastating and is a major contributor to urban seismic risk.

Shallow surface movement – movement that is shallow and limited to surface layers, such as that caused by liquefaction of soils or landslip.

Slow ground movement – the rate of movement is normally considered to be gradual and imperceptible, and typically measured over a period of several years. Also known as creeping land movement.

Subsidence – occurs when earth and rock fall into a cavity that has formed below the ground’s surface. It is a natural process, although it can also occur as a result of people’s activities, for example, landfill and mining. Gradual geothermal subsidence can also occur when deep-seated pressures decline over time.

Sudden ground movement – movement of the earth’s surface from earthquakes (most common), explosions, landslides and subsidence.

Uniform block shift – consistent translation and rotation in a manner that maintains shape but not position or orientation.

What is an affected boundary?

An affected boundary is defined in rule 108 as a boundary where ground movement has distorted the land in excess of the relevant accuracy tolerances and that has not been subsequently defined by survey and recorded in an approved CSD. The applicable accuracy tolerances are set out in rule 27(1) (boundary points), rule 29(2) (water, water centreline and irregular boundaries), and rule 57 (permanent structure boundaries). Both horizontal and vertical boundaries can be affected by ground movement.

The following diagrams illustrate ground movement scenarios and whether a boundary is considered affected.

Figure 1 below illustrates where the distortion of a right-line boundary due to ground movement is less than the accuracy tolerances which means it is not an affected boundary.

Boundary not affected by ground movement

Figure 1: Boundary not affected by ground movement

Figure 2 below illustrates a class A, B or C boundary where ground movement has distorted the land by more than the relevant accuracy tolerances. The boundary is an affected boundary and will need to be defined by survey unless it is permitted to be accepted. In this example the distortion is not due to fault zone movement or to Canterbury earthquake movement and therefore the boundary is re-established in its original position.

Class A B or C boundary which is an affected boundary

Figure 2: Class A, B or C boundary which is an affected boundary

Boundaries affected by fault zone movement

The redefinition of a boundary affected by fault zone movement must reflect the distortion resulting from the deformation of the bedrock (r 109(2)).

Some affected boundaries may have changed orientation, been extended, compressed, or changed shape (distorted) as a result of the ground movement. When defining by survey, examples of redefining in terms of fault zone movement include:

  • the creation of new boundary points at new angles in a right-line boundary
  • new bends in an irregular or water boundary
  • showing a difference in the shape of a permanent structure boundary
  • redefining the RLs of height-limited boundaries.

A boundary changed by fault zone movement will hold the same relationship to relevant physical evidence as it did prior to the earthquake. For example:

  • A boundary that coincided with a fence line will continue to coincide with that fence line.
  • Boundary points will retain the same relationship to nearby survey marks affected by the same localised movement.

Figure 3 below illustrates scenarios where fault zone movement has distorted existing parcel boundaries.

Illustration A shows a distorted boundary within the accuracy tolerances hence no new boundary angles are created. The boundary must retain its original shape.

Illustration B shows a distorted boundary outside of the accuracy tolerances hence new boundary angles must be created. These boundaries require the annotation on the CSD title diagram, “Boundary includes new angles due to fault zone movement” (r 104).

Existing parcel boundaries distorted by fault zone movement

Figure 3: Existing parcel boundaries distorted by fault zone movement

A boundary of land subject to uniform block shift resulting from fault zone movement will have maintained its relativity with local survey marks and other physical evidence although its absolute geographic position will have changed. In these cases, the local survey marks and other physical evidence will be able to be used in re-establishing the boundary in terms of that block shift.

Water and water centreline boundaries affected by ground movement

An affected water boundary that is to be retained in its former position under rule 10(2) or (3) must be accepted (r 109(4)). The affected water boundary does not have to account for erosion and accretion that occurred prior to the ground movement.

Likewise, an affected water centre-line boundary that is to be retained in its former position under rule 11(2) must be accepted (r 109(5)).

Where the affected boundaries are accepted under rules 109(4) and (5), the annotation “Boundary not surveyed since ground movement” must be added against the relevant boundary on the title diagram (r 104).

For further information on water and water centreline boundaries see the following guidelines:

Defining new non-primary parcel boundaries over affected underlying parcels

Rule 110 is applicable to cases where the underlying parcel is not being created by the survey. Two scenarios are provided for:

(a) boundaries affected by Canterbury earthquake movement, and

(b) boundaries affected by movement other than Canterbury earthquake movement.

In scenario (a), if a new non-primary parcel boundary coincides with or intersects an affected underlying parcel boundary that is class A or B, the underlying parcel boundary must be defined by survey and ground marked if practicable (r 110(2)).

For further information see the guideline about Re-establishing Canterbury earthquake affected boundaries in greater Christchurch

In scenario (b), the non-primary parcel boundaries may be inaccurately determined and the requirements in rule 51(2) apply.

For more information see Defining non-primary parcels using the control network

New unit title and cross lease developments

If a new unit title or cross lease development is to be created over an existing primary parcel with affected underlying boundaries, then a new underlying parcel must be created before the development can deposit (r 110(4)(a)). All affected boundaries must be defined by survey (r 109(1)).

A new underlying parcel must also be created where any of the affected boundaries of the underlying parcel have already been redefined, but not recorded in the tenure system. An example of this is an affected boundary redefined in a boundary reinstatement Survey Office (SO) CSD.

A new development can be interpreted as where there is no existing unit title or cross lease development or where an existing development has been cancelled.

For registration under the Land Transfer Act, creating a new underlying parcel requires a LT CSD defining the full extents of the underlying parcel. This CSD will need to be approved prior to the unit title or cross lease CSD being submitted.

Existing unit title developments

Underlying affected boundaries on an existing unit title development that retains a record of title may be accepted, provided that a new non-primary parcel boundary does not coincide or intersect with it (r110(5)).

Also see Unit plans in areas of ground movement

Height-limited boundaries

For height-limited boundaries where there has been uniform uplift or subsidence of the ground surface over the full horizontal extent of the height restricted boundary, then the boundary is not an affected boundary. The boundary may have moved either upwards or downwards with the ground movement and any pre-ground movement reduced level (RL) defining the height-limited boundary may be no longer correct. A height-limited boundary may remain unaffected even where it has moved in a vertical direction that is different to vertical movement affecting related PRMs. If a potential RL change to an existing height-limited boundary is identified, then it is suggested advice should be sought from LINZ.

Where height-limited boundaries are recorded on an existing unit development then all reduced levels must be expressed in terms of the previously deposited CSD for the unit title development (r 62). The requirements for referencing a new height restricted boundary point are detailed in rule 61.

If an unofficial datum is used under rule 62(1), then one or more vertical control marks within 1000m of a new height-limited boundary must be included in the survey (r 18(2)). If no vertical control mark exists within 1000m then a vertical control mark at any distance must be included in the survey (r 18(3)). The vertical control mark used must be provided with a reduced level in terms of the existing unit title development datum.

For more information see Permanent reference marks and vertical control marks for height-limited boundaries

Ground marking and occupation information

Rule 109(1) requires each point on an affected primary parcel boundary to be marked, if practicable.

A boundary reinstatement survey may be used to mark a boundary point that is on an affected boundary, but it must be a complex boundary reinstatement survey. (r 114(2)(b)).

For more information see Complex boundary reinstatement and CSD requirements

An existing boundary mark that is deemed disturbed and no longer marks the boundary may be removed or driven below the surface under rule 37(1). Disturbed survey marks must be treated as a new survey mark. Where a survey mark is removed, the disturbed position must be recorded in the record of survey and survey diagram along with an annotation to indicate the mark has been removed (rr 80(1), (2), (5), 82(a), (b), (c) & 89(b)).

Occupation information in accordance with rule 81(2) must be provided in relation to any affected boundary points that are required to be marked by rule 109(1).

For more information see Occupation and physical features

Survey reporting

Rule 6(a) requires a surveyor to 'gather all evidence relevant to the definition of the boundary and its boundary points' when defining a boundary by survey. Rule 72(i) requires information considered in reaching decisions made about defining an existing boundary by survey to be included in the survey report.

Examples of relevant evidence where there has been ground movement may include:

  • the condition of reference and boundary marks and the ground conditions immediately surrounding these marks
  • visible evidence of a fault trace, slump lines, or liquefaction of soils
  • broken or cracked fencing or kerbs or building foundations
  • visible evidence of repair to, or reinstatement of, occupational features damaged by soil liquefaction or fault trace
  • photographic evidence including historical aerial photographs or photographs taken immediately before and after the ground movement event
  • local knowledge from occupiers, neighbours, and present or past owners
  • Local Authority records
  • news media articles
  • engineering reports.

The survey report should include details of the investigations carried out to determine the type and nature of the ground movement. Factors such as historic movement in the locality, soil geology, seismic events, climate events and manmade earthworks could have had an influence on the ground movement.

For more information on reporting see Content of a CSD – Survey report

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