Geomorphological Assessments

Geomorphological assessments cover the geology, landform evolution (which often must include the Holocene and Pleistocene Epochs), present forms and processes, and predict future change for various scenarios including climate change projections. Such assessments provide the basis for all our investigations.    The following areas of coastal investigation in which we work often result from protection and management legislation of which the Resource Management Act (RMA 1991) and the New Zealand Coastal Policy Statement (NZCPS 2010) are the most relevant.  Implicit, and in some situations, explicitly stated in giving effect to the requirements of the legal directives is coastal geomporphology.


Coastal Environment

Policy 1 of the New Zealand Coastal Policy Statement (NZCPS, 2010) refers to the coastal environment and lists a range of determinants to be considered in its demarkation. Geomorphology plays a central roll in identifying the landward extent of the coastal environment and some counicls are also defining a corresponding Coastal Protection Area in District Plans.    

Natural Character

Section 6(a) of the RMA refers to preservation of natural character and NZCPS (2010) Policy 13 provides instruction on its preservation with geomorphology again playing a central roll.  Local government Plans are now beginning to incorporate Natural Character.

Outstanding natural Landforms and Landscapes

Section 6(b)  of the RMA refers to the identification and protection of outstanding natural features and landscape and NZCPS (2010) Policy 15 describes protection measures including identification with geomorphology playing a key roll. Local government Plans are beginning to incorporate outstanding natural landforms and landscapes.

Coastal Management

Section 5 of the RMA refers to the promotion of sustainable management of natural and physical resources, and understanding the geomorphology is necessary to achieve this objective. Many coastal reserves have Coastal Management Plans which are regularly updated.  In addition, these plans may required Resource consents.  Geomorphological assessments are the starting point for any such planning/management.   In addition, most of the NZ coast is eroding or unstable (fluctuating shoreline) and sand stabilization programmes are required. Again, resource consents may be part of such programmes and once again geomorphological assessments are the starting point for any such programmes.


Tangata whenua

Present revisions planned for the RMA will give Maori more influence in resouce management and protection, and the NZCPS 2010, Policy 2, list measures that must be taken into account when giving effect to the Treaty of Waitangi in relation to the coastal environment.   Maori have a unique association with the land, especially the coast, so natural processes that maintain or change it are of fundamental importance when it comes to participating in development decisions.  Maori have invariably lacked such specialist scientific knowledge and CSL have been  able to unravel the local geomorphology and present it in a clear and effective way.


Coastal Hazard assessments

Coastal hazards can threaten infrastructure, property and personal safety, and include the following erosion of beach, dune, inlet and cliff; burial by wind-blown sand or cliff failure;  inundation from tsunami, storms and hinterland flooding, and waves and currents (especially rips) threatening beach users.

Local Government Plans have, in the past, had some form of hazard zoning to control building development; however, assessment methods and the resulting implementation into landuse zoning could vary considerably between practitioners and councils. The revised NZCPS (2010) Policy 24 provides a range of criteria to more consistently assess the potential hazard, and Local Government agencies  (District and Regional Councils) are now having their assessments updated.  Of particualr note is Policy 24  (1)(c) which specifically refers to assessments having regard for geomorphological character.

Policy 24 also refers to potential hazard and hazard risk and this is addressed by identifying the unlikely level of occurrence (1 to 9% chance) with the High Court recently requiring the worst case (less than 1% chance) be used. To assist planners in converting hazard risk into District Plan zones (Policy 25 and 27) for different types of development e.g. new infrastructure, subdivision, additions to existing buildings etc), relative probabalistic software has now been developed that defines a continuum of probabilities rather than the single low probability (potential) value required in an assessment. CSL assisted in the development of this software and, unlike most other consultances in New Zealand, we are thus able to apply the technique in our erosion hazard assessments.

Policy 24 requires the assessment period now be at least 100 years compared with 50 years (Building Act) or even just 10 years (District Plan review period) as used prior to 2010. In addition, climate change effects must be incorporated within the assessment rather than just be considered.   These requirements have resulted in hazard setbacks moving landward, in some cases substantially, and, while updated assessments have been implemented into District Plans in some areas, extreme resident outcry has occurred in two densely settled coastal areas.

Kapiti Coast and Peagus Coast

Coastal Systems Ltd (CSL) carried out Kapiti Coast erosion hazard assessments in 2008 with a 50 year prediction period and then again  in 2012 with a 100 year prediciton period.  We would argue that these were the most detailed district wide assessments ever carried out in New Zealand in terms of the range of coastal types, different levels of protection in different areas and the thoroughness of the methodology.  Tonkin and Taylor Ltd (T+T) carried out the Christchurch coast hazard assessment in 2015 using a 100 year prediciton period and the newly developed relative probabalistic analysis (RPA).

On both coasts, residents claimed that the coastal erosion prediction lines would result in falling property values (which evidence does not support) and aroused intense political and media pressure which, in each case, resulted in the appointment of independent expert panels to review the practitioner’s assessments. In each case the panels found that the assessments were fit for purpose (for use in District Plan landuse zoning) after minor modification were made, and they recommended this be carried out forthwith.  Kapiti residents also filed for a High Court judicial review seeking an exemption to assessment findings appearing in LIM reports. However, the court found that the council had no such discretion and had to inform purchasers of potential erosion information it “was aware of”.

While the assessments from both areas were viewed similarly by experts, the council responses were dramatically different.  At Kapiti, the newly elected council now sympathised with residents and ignored the panel recommendation to modify and use forthwith. The assessments and implementation process (district Plan review) were shelved in 2014. The Kapiti District Council said that it would carry out a more detailed assessment by 2018, but this process has yet to begin. Furthermore, the assessment’s erosion information does not appear on LIM reports.  By contrast, at Christchurch, the council is following the panel’s recommendation and proceeding with modification, implementation into the District Plan, and relevant erosion information is appearing on LIM reports.

Click here for our more detailed review of these erosion hazard sagas, including downloadable assessments and hazard prediction lines. Prospective home buyers on the Kapiti Coast are urged to consult these lines when considering purchasing a home as the zoning the council is presently using dates back to the 1980s.

Hearing presentations

The final stage of many projects is to present evidence at hearings.  Hearing pannels and judges can struggle with the technicallty of our work so we strive to ensure our reports are clear, comprehensive and well illustrated.



As well as locating, processing and analysing available historical data (maps, aerial photography, satellite images, video, bathymetric charts, survey plans, profiles etc) we also have the capability to collect and process raw data as required by a project.