Download Social, cultural, environmental, and economic impacts from harbour

Social, cultural, environmental, and economic impacts
from harbour and coastal erosion
The following information identifies some of the likely impacts of coastal and harbour erosion on the
Western Bay of Plenty District. The information has been categorised as social, cultural,
environmental or economical.
Information is drawn from Wellington City Council’s ‘Sea level Rise Options Analysis’, as well as
Western Bay and Bay of Plenty Regional council’ information on ecological, archaeological and
heritage sites.
Social
Predicting the potential social effects of coastal and harbour erosion is complex, as they will largely
be determined by the approach taken to address erosion. Below are possible effects:
Recreation values
Harbour and coastal areas play a significant role in the life of New Zealanders and are often valued
for the recreation activities that they provide.
Recreational activities (sun bathing, picnicking, swimming, surfing, fishing, boating, diving, etc.) may
be affected if existing beaches are reduced in width or disappear altogether.
Social inequality
Coastal protection usually costs more than the market value of undeveloped rural land, but
less than the value of developed land and structures. Coastal protection works are therefore more
likely to be prioritised in areas with higher land value.
This may lead to inequality in areas with lower land values (typically areas with lower socioeconomic
characteristics, rural areas and conservation areas), where residents will be at greater risk of the
social effects of displacement.
Political and social tensions
Political and social tensions may arise as a result of the measures undertaken to address harbour
and coastal erosion. For example, the large investment required in coastal and harbour areas may
not be considered an appropriate economic response by people living elsewhere.
Community well-being
Many of the social effects noted above can impact on the well-being of the community as a
Whole. However, a positive impact on community well-being from harbour and coastal erosion can
be an increase in community empowerment.
Displacement can also contribute to problems of overcrowding on the remaining land,
depending on how much suitable land remains, and how well the resettlement is managed.
Overcrowding has a knock-on effect on health.
Health - Living with stress and uncertainty
Mental health issues including anxiety, depression and suicide can arise from the loss of property,
historic and cultural sites of value, community networks (if people are forced to relocate, income,
displacement from homes, and the uncertainty of risk).
Cultural
There are numerous cultural and historical areas/assets in the District located along coastal and
harbour margins.
For example, in the Regional Coastal Environment Plan the whole of Te Awanui (Tauranga Moana or
Tauranga Harbour) has been recognised as being an area of significant cultural value. Traditionally,
Te Awanui was as significant, if not more so, than the land to tāngata whenua. It was the source of
kaimoana and the means of access and communication among the various iwi, hapū and whānau
around its shores.
Te Awanui is rich in cultural heritage sites for Waitaha and the Tauranga Moana iwi. Many of these
sites are recorded in Iwi and Hapū Management Plans and other historical documents and files.
View a map of the District’s archaeological sites near the coast or harbour. The archaeological and
cultural heritage sites are also listed in Appendix 3 of the District Plan.
In the Western Bay District there are three marae located on, or near, the open coast and 11 directly
located on, or near, the inner harbour margins. These are:
Coastal Marae
Otamarakau
Te Awhe o te Rangi
Whakaue Kipapa
Inner Harbour Marae
Otaawhiwhi
Tuapiro
Te Rereatukahia
Te Rangihouhiri
Kutaroa
Opureora
Opounui
Rangiwaea
Tutereinga
Poututerangi
Paparoa
Location
Otamarakau
Maketu
Maketu
Bowentown
Tuapiro
Katikati
Matakana
Matakana
Matakana
Rangiwaea
Rangiwaea
Te Puna
Te Puna
Te Puna
Environmental
Numerous effects could occur on the environment – the nature and severity of which depends on
what efforts are taken to combat erosion.
Both the Regional Coastal Environment Plan and the Western Bay District Plan have recognised and
mapped areas of ecological significance around the harbour and open coast. The dune and wetland
environments are of particular significance for nationally and regionally threatened species. Other
rare and threatened coastal habitats include coastal forest, seagrass beds, saltmarshes and intertidal
flats.
Approaches
Taking a ‘hard defences’ approach could result in immediate adverse environment effects such as
loss of scenic quality, loss of access, loss of resilience to storm attack and reduction of sediment
supply to the coast. Medium term effects could include beach narrowing, loss of sediment, loss of
amenity, and loss of natural habitat.
The benefits of this are that the beaches are maintained, a natural coastal landscape is
created/preserved, a functioning coastal ecosystem is preserved/created and the amenity value of
the coast is sustained.
Wave reflection from sea walls worsens loss of sediment from beaches. In the long term the natural
sedimentary system is altered as sediment that was formerly yielded by coastal erosion is no longer
available and thus the coastal ecosystem adjusts. This necessitates changes elsewhere in the coastal
system outside the area directly affected the defences.
In the case of ‘groynes’ (hard jetty-like structures) or offshore breakwaters the natural coastal
system is altered and its ability to cope with changing environmental conditions (sediment supply,
storms, seal leave change) is reduced. The net effect is to require yet more coastal engineering
intervention. The ultimate manifestation of this approach is the replacement of all sandy coasts with
hard defences e.g. Taiwan.
Beaches and dunes may suffer erosion as a result of the reduction of sediment input. The marine
ecosystem may suffer from lack of sediment inputs.
There are no negative environmental impacts from a ‘managed retreat’ approach. Managed retreat
offers the opportunity for potential environmental enhancement as new tidal salt marshes are
encouraged to expand.
With a ‘soft defences’ approach there is evidence that recharged beaches do have poor fauna and
flora compared to natural beaches, especially in short to medium term and thus a negative impact
on the ecosystem is likely to be the major immediate societal cost.
Nicety
Some hard structures (e.g. seawalls, groynes) can affect factors that contribute to the environment’s
amenity values, such as visual effects, natural character, and public access.
Economic
Economic impacts can include loss of productivity of land, infrastructure and property.
Loss of property and land
Harbour and coastal erosion may adversely affect peoples’ incomes due to a loss of rural productive
land. Erosion on or nearby a property can result in a reduction in the value or price of the property.
Affected property owners could also find that it is difficult to get insurance or a mortgage for
housing if it has or is likely to be affected by erosion.
The loss of property will arise if coastal protection works are not undertaken, or are not successful.
People may not be able to afford to repair or even demolish damaged property. Related to this are
the potential costs associated with relocating a house or in the case of loss of a dwelling the costs
associated with buying or renting another home.
Commercial
Depending on how council addresses coastal and harbour erosion it has the potential to affect
commercial fisheries and the aquaculture industry by damaging coastal wetlands and changing the
water quality of estuarine areas. Communities dependent on coastal or harbour tourism could
experience a decrease in tourist expenditure.
The reduced productivity of businesses that rely on infrastructure which is affected by erosion (such
as the transportation network), or which incur costs in mitigating erosion, will have a knock-on effect
on the local economy.
Community infrastructure
Coastal and harbour erosion may compromise the performance of surface and stormwater drainage
systems in low-lying coastal settlements. Erosion could also damage transport infrastructure (roads
and rail) by flooding and/or eroding roads. Changes in sedimentation around the coastline could
affect navigation routes. Coastal and harbour walkways/cycleways can also be at risk.
This infrastructure has been paid for by residents through rates and tax. Therefore, the reallocation
of public funds to flood hazard protection, infrastructure repair and upgrade, and disaster relief is a
cost to the community.
Erosion protection works
Council is responsible for nearly 100 existing legally consented coastal protection structures. These
range from sand tubes to timber walls to rock revetments. They are of various ages, in various states
of repair and have a range of replacement lifespans up to 75 years. In total they have a current
replacement value in excess of $12.5 million.
The assessment of their condition and likely effective longevity has not to date factored in sea level
rise. With all hard defences any rise in sea level will have to be countered by raising the structures
heights if they are to remain effective. This will be an expensive activity and ultimately may prove
unaffordable and unachievable.