Erosion and accretion

What happens to public access if a water margin reservation (unformed legal road, marginal strip, esplanade or another public reserve) is submerged by a gradual but permanent movement in the course of a river, the level of a lake or the high tide mark on the coast (erosion)?

The reserved land stays where it is, and public access on dry land will be lost if the full width of the reserved land is submerged. 

Are there any exceptions to this?

Two forms of public access alongside rivers, lakes or the ocean move with any movement in the water margin. These are esplanade strips (as distinct from esplanade reserves) and marginal strips that were established from 10 April 1990. These forms of access are not affected by movements in the related water margins.

What happens to public access when a gradual but permanent movement (accretion) in the course of a river, the level of a lake or the high tide mark on the coast results in the water margin moving away from the original water margin reservation (unformed legal road, marginal strip, esplanade or another public reserve)?

The unformed legal road or other reservation increases in width as the water retreats. The additional land becomes legally the same as the original reservation. Public access is not lost. In the case of the exceptions referred to above (movable marginal strips and esplanade strips), the public access remains the same width alongside the water margin.

How do erosion and accretion affect private property?

Erosion along a water margin, if it advances through private property, results in land being lost to the advancing water body. Accretion along a water margin that forms the boundary of private land (where there is no public reservation along the water margin) results in a gain to the private land.

How are these movable water boundaries defined?

It depends on the definition of the boundary in the survey plans of the particular land parcel. An indication can be gained from the current statutory definitions of riverbed, lake bed and foreshore (or the coastal and marine area). 

For example, riverbeds and lake beds in the Conservation Act 1987 are defined as:

(a)   in relation to any river, the space of land which the waters of the river cover at its fullest flow without overtopping the banks; and

(b)   in relation to a lake, the space of land which the waters of the lake cover at its highest level without exceeding its physical margin.

In the Marine and Coastal Area (Takutai Moana) Act 2011 the marine and coastal area … means the area that is bounded,

(i)   on the landward side, by the line of mean high-water springs.

Coastal land parcels were, however, commonly, but not always, surveyed to the mean high water mark.

How did these laws come about?

The law on water margin boundaries combines inherited English common law, Crown subdivision rules and practice, New Zealand judicial decisions, and New Zealand legislation. This history cannot be undone and has resulted in a complex mix of property rights.

How can I determine the impact of erosion and accretion on public access along water margins?

The impact may be discerned from a study of the legal boundaries and the topographical and photographic view of an area in the Herenga ā Nuku mapping system. The legal effects can, however, be quite complicated and require expert advice. Herenga ā Nuku is happy to help, but where there are differences over legal boundaries, these may sometimes only be able to be resolved by the Courts.