The doctrine of accretion and erosion applies to boundaries of tidal lakes and both tidal and non-tidal streams and waterways where the change in the position of the bank of the waterway is natural, gradual and imperceptible. Where this situation does not apply, the bank must be defined in the same position as immediately before the change.
The doctrine of accretion and erosion does not apply to non-tidal lakes.
This occurs where water recedes from the land, or where land builds up by alluvial deposits as added by horizontal progression outwards from the bank (or shoreline).
Accretion does not apply where there has been a vertical development over a wide area rather than a gradual extension of existing land.
For example, where a fast flowing river deposits sand and silt in a fan shaped pattern at the entrance to a lake, so as to cause the lake bottom to appear above the water level and eventually join to the land, accretion does not apply. [Refer Bulman 57 D.L.R. (2d) 658 British Columbia Supreme Court]. This is so even where the land becomes arable by the gradual advance of top soil across the raised lake bottom from the existing land.
Further, where accretion is claimed, the opposite bank of the stream must also be plotted as defined in the existing current plan. In the absence of a definition in that plan, it will be plotted in accordance with its relationship to the near bank as shown in prior plans or maps.
In respect of lands alienated on or after:
- 3 May 1918 in the Eastern and Central Divisions and
- 31 May 1935 in the Western Division
any variation shown in a plan from the line of the river bank as at the date of alienation will require the approval of Crown Lands. By the operation of s.172 Crown Lands Act 1989 (formerly s.235A, Crown Lands Consolidation Act, 1913), title to the beds of all rivers, adjoining lands alienated on or after that date, is vested in the Crown.
Note 1 The Doctrine of Accretion as it applies to the definition of the MHWM of the coastline or a tidal river was modified by the introduction of s.55N Coastal Protection Act 1979 on 7 February 2003 see Tidal boundaries (MHWM).
Note 2 The general law of accretion applies even though the gradual and imperceptible build-up has been unintentionally assisted, or would not have taken place without, the erection of groynes etc for the purpose of protecting the shoreline from erosion.
This is the natural and gradual retreat of the bank into the adjoining land caused by the action of a river or stream. The change in the position of the bank must only be discernible over a significant period of time not as a result of a sudden storm or flood.
Note In cases where erosion has occurred suddenly (ie the process did not occur in a natural, gradual and imperceptible manner) the former definition of the bank will not change. In these cases the natural feature boundary may extend into the water and the parcel will include part of the actual stream-bed or waterway.
Where accretion or erosion is disclosed, the surveyor must furnish a report indicating whether the change in position of the river is due to:
- a gradual and imperceptible movement by natural means
- a sudden shift, as would happen in flood time
- differences caused by adopting either high or low banks or
- errors in the basic survey information, which may mean that the river has not changed its course at all.
In addition, the surveyor must furnish any other evidence available to support the definition eg statutory declarations by local residents with the necessary knowledge of how the change took place.
When received in NSW LRS the evidence requested will be considered, together with any related aerial photographs of the area, and a decision will be made as to whether the definition in the plan is acceptable.