Coastal inundation

What we know

Factors contributing to coastal inundation

Coastal inundation is primarily caused by storm surges, high or extreme tides raising sea levels, and larger than normal waves or swell.

Factors contributing to inundation (Tonkin & Taylor Ltd, 2017).

These effects can be exacerbated when these storms occur at the same time as extreme tides. The extent and depth of flooding is also influenced by the physical characteristics of the land adjoining the coast . Further information on the process of coastal flooding in outlined in the Ministry for the Environment Fact Sheet: http://www.mfe.govt.nz/sites/default/files/media/MFE_Coastal_Fact%20Sheet%202.pdf


Sea level rise will increase the frequency of coastal inundation

As sea levels continue to rise the frequency, duration and extent of coastal flooding will increase. This will cause king tides, storm surges and waves to reach higher up the shore than they used to, and increase the likelihood of cumulative effects.

While coastal inundation from a 1 in 100-year event is considered rare in todays’ terms, this can be expected to occur once a year in Christchurch with as little as 0.3m of sea level rise. If sea level continues to rise, the same inundation event can be expected to occur every tide.

The four RCPs recommended by the Ministry for the Environment are used to estimate future sea level rise for a range of possible futures.


Exposure to coastal inundation

Coastal inundation which would flood from the Estuary/Ihutai will likely affect a large percentage of the Regeneration Strategy project area with as little as 0.3m sea level rise (the minimum likely to occur in the next 50 years).

Coastal inundation - number of properties affected

Here's a map showing the coastal inundation hazard for the years 2065 and 2120 for all four RCP scenarios, based on the Coastal Hazard Assessment for Christchurch and Banks Peninsula (Tonkin & Taylor Ltd., 2017).


Why this is important

See Modelling coastal erosion and inundation for more information.


What we know

Factors contributing to coastal inundation

Coastal inundation is primarily caused by storm surges, high or extreme tides raising sea levels, and larger than normal waves or swell.

Factors contributing to inundation (Tonkin & Taylor Ltd, 2017).

These effects can be exacerbated when these storms occur at the same time as extreme tides. The extent and depth of flooding is also influenced by the physical characteristics of the land adjoining the coast . Further information on the process of coastal flooding in outlined in the Ministry for the Environment Fact Sheet: http://www.mfe.govt.nz/sites/default/files/media/MFE_Coastal_Fact%20Sheet%202.pdf


Sea level rise will increase the frequency of coastal inundation

As sea levels continue to rise the frequency, duration and extent of coastal flooding will increase. This will cause king tides, storm surges and waves to reach higher up the shore than they used to, and increase the likelihood of cumulative effects.

While coastal inundation from a 1 in 100-year event is considered rare in todays’ terms, this can be expected to occur once a year in Christchurch with as little as 0.3m of sea level rise. If sea level continues to rise, the same inundation event can be expected to occur every tide.

The four RCPs recommended by the Ministry for the Environment are used to estimate future sea level rise for a range of possible futures.


Exposure to coastal inundation

Coastal inundation which would flood from the Estuary/Ihutai will likely affect a large percentage of the Regeneration Strategy project area with as little as 0.3m sea level rise (the minimum likely to occur in the next 50 years).

Coastal inundation - number of properties affected

Here's a map showing the coastal inundation hazard for the years 2065 and 2120 for all four RCP scenarios, based on the Coastal Hazard Assessment for Christchurch and Banks Peninsula (Tonkin & Taylor Ltd., 2017).


Why this is important

See Modelling coastal erosion and inundation for more information.