Infrastructure

What we know

River and Estuary edge structures

A range of formal and informal structures along the estuary edge, provide some short-term protection to infrastructure and development from inundation and erosion.

Temporary stopbanks along the narrow section of the estuary edge at the Pages Road end are being reinforced and stabilised. When this work is completed the temporary stopbanks will provide continuous protection as far south as Bridge Street. At the time of construction the temporary stopbanks were designed to protect the surrounding area from a 1 in 50-year flood which range in height up to 11.4m above the Christchurch Drainage Datum for Christchurch, and will have a design life of 20 years. There has also been a range of activities undertaken as part of the Christchurch City Council’s temporary stopbanks project North of Bridge Street such as rock work, terramesh baskets, pipe replacement, tree removals and planting, building paths and trails, and top soiling.

A minor extension to the temporary stopbanks is planned for the first 185m immediately south of Bridge Street, although the rest of the extension to the jetty has been deferred and will be considered as part of the range of options explored in the Regeneration Strategy.

Along the estuary edge in Southshore there is a mix of natural edge, Christchurch City Council-owned structures, old sea walls and informal protection structures. Many structures were installed by private landowners along the estuary edge. It is not known whether these were consented or engineered to a particular design standard, and some structures have deteriorated or been displaced by the earthquakes.

In 2016 central government agencies constructed an informal landscaping bund along the estuary edge of the residential red zone. This may have reduced the risk of inundation in the short term. The Christchurch City Council filled in gaps in the bund and extended the bund in Jellicoe Marsh and around the South Brighton Holiday Park as part of a series of emergency works during flood events. Other recent works include rebuilding of the rock structures in front of the boardwalk in South New Brighton Reserve, and maintenance on the Ebbtide Street rockwall.

Short term and temporary stabilisation works as part of ongoing monitoring and maintenance may occur in front of the landscaping bund in Southshore and other bunds along the estuary edge in the interim of a long term strategy for the area. In addition pump setdown areas are planned to facilitate future temporary pumping in identified locations.


A stopbank and a bund can perform the same function, but a bund is generally a structure that might not be constructed to the same engineered standard as a stopbank, and may be more temporary or informal in nature.


Stormwater

The majority of stormwater services run the along Rocking Horse Road and Estuary Road, with outflows into the Estuary/Ihutai. Because some of the roads in the Regeneration Strategy project area are located below the high tide level, In order to allow them to drain, the stormwater outlets discharge into the Estuary also below high tide level.

This means the outflows are restricted when the tide is high and can lead to water flowing back through the system in dry weather if there is leakage in the backflow prevention. In order for this system to work effectively they need to be able to both open and close as required. CityCare manages this issue by clearing these drains of any silt build up before significant rain events.

The stormwater pipe network is designed to deal with a 1 in 5-year rainfall event, and can manage around a 1 in 10-year event through secondary flow paths including flooding on roads. Where heavy rain coincides with a high tide, temporary pumps may be needed and are deployed in the locations in shown in figure 12 as necessary.

Stormwater ponds at the end of Blake Street were built in 2014/2015 by SCIRT as part of a wider stormwater system including a pump station, designed to discharge stormwater into the estuary at all tide levels. The work also included a stormwater pipe network involving a large chamber and outlets, and an overland flow path.


Wastewater

The SCIRT programme introduced the use of pressure and vacuum sewer systems to improve resilience in areas with high risk of liquefaction, including across the Regeneration Strategy project area . The sewerage pipes run along Rocking Horse Road and spread out more extensively throughout South New Brighton with outflows at Penguin Street, Beatty Street, Kibblewhite Street, Admirals Way and the ocean outfall at Jellicoe Street. The ocean outfall takes the city’s treated wastewater from the oxidation ponds and transports it three kilometres out into Te Kaikai a Waro/Pegasus Bay. This was completed in December 2009 and cost $87 million.

Here's a map that shows the Council's stormwater and wastewater infrastructure in Southshore and South New Brighton.


Water Supply

The water supply for the Regeneration Strategy project area is fed from groundwater sources beneath Christchurch. The local pump stations are not subject to the temporary chlorination that much of the rest of the city is still experiencing, as the below-ground well heads have been checked and cleared of the risk for contamination. Water treatment by chlorination is not part of the long-term strategy for water supply as outlined in the Christchurch City Council 2018 Infrastructure Strategy.


Transport

Estuary Road, Union Street, Marine Parade (north of Bridge Street), and Rocking Horse Road (to the south of Caspian Street) provide the main transport routes within South New Brighton and Southshore. Bridge Street, including the Bridge Street Bridge, is classified as a minor arterial route in the Christchurch Transport Strategic Plan, highlighting its importance as the key connecting route to the rest of the city.


Why this is important

All infrastructure is vulnerable to the effects of climate change. Various upgrades following the earthquakes have improved the resilience of some systems, such as the wastewater, at least in the short to medium term. However, other systems, such as stormwater is highly vulnerable to the effects of climate change as the discharge points are often at the lowest elevation near the coast. These services are likely to experience increased failures and decreases in levels of service over the coming decades as sea level rises .

To date, responses to improve the resilience of infrastructure in the Regeneration Strategy project area have been ad hoc and reactionary, such as the response to the earthquakes, or individual flood events. The Regeneration Strategy provides an opportunity to take a strategic and adaptive approach to infrastructure management and investment that recognises future uncertainties, and the impacts of climate change.


What we don’t know

In its 30 Year Infrastructure Strategy 2018-2048, the Christchurch City Council has made no long-term commitments to defend areas and services from the effects of climate change. However, many asset management programmes now take climate change effects into account, such as design guidance for new infrastructure which adds allowances for increased rainfall intensity and sea level rise. The Council is also carefully considering how and when it constructs new infrastructure in areas affected by climate change.

What we know

River and Estuary edge structures

A range of formal and informal structures along the estuary edge, provide some short-term protection to infrastructure and development from inundation and erosion.

Temporary stopbanks along the narrow section of the estuary edge at the Pages Road end are being reinforced and stabilised. When this work is completed the temporary stopbanks will provide continuous protection as far south as Bridge Street. At the time of construction the temporary stopbanks were designed to protect the surrounding area from a 1 in 50-year flood which range in height up to 11.4m above the Christchurch Drainage Datum for Christchurch, and will have a design life of 20 years. There has also been a range of activities undertaken as part of the Christchurch City Council’s temporary stopbanks project North of Bridge Street such as rock work, terramesh baskets, pipe replacement, tree removals and planting, building paths and trails, and top soiling.

A minor extension to the temporary stopbanks is planned for the first 185m immediately south of Bridge Street, although the rest of the extension to the jetty has been deferred and will be considered as part of the range of options explored in the Regeneration Strategy.

Along the estuary edge in Southshore there is a mix of natural edge, Christchurch City Council-owned structures, old sea walls and informal protection structures. Many structures were installed by private landowners along the estuary edge. It is not known whether these were consented or engineered to a particular design standard, and some structures have deteriorated or been displaced by the earthquakes.

In 2016 central government agencies constructed an informal landscaping bund along the estuary edge of the residential red zone. This may have reduced the risk of inundation in the short term. The Christchurch City Council filled in gaps in the bund and extended the bund in Jellicoe Marsh and around the South Brighton Holiday Park as part of a series of emergency works during flood events. Other recent works include rebuilding of the rock structures in front of the boardwalk in South New Brighton Reserve, and maintenance on the Ebbtide Street rockwall.

Short term and temporary stabilisation works as part of ongoing monitoring and maintenance may occur in front of the landscaping bund in Southshore and other bunds along the estuary edge in the interim of a long term strategy for the area. In addition pump setdown areas are planned to facilitate future temporary pumping in identified locations.


A stopbank and a bund can perform the same function, but a bund is generally a structure that might not be constructed to the same engineered standard as a stopbank, and may be more temporary or informal in nature.


Stormwater

The majority of stormwater services run the along Rocking Horse Road and Estuary Road, with outflows into the Estuary/Ihutai. Because some of the roads in the Regeneration Strategy project area are located below the high tide level, In order to allow them to drain, the stormwater outlets discharge into the Estuary also below high tide level.

This means the outflows are restricted when the tide is high and can lead to water flowing back through the system in dry weather if there is leakage in the backflow prevention. In order for this system to work effectively they need to be able to both open and close as required. CityCare manages this issue by clearing these drains of any silt build up before significant rain events.

The stormwater pipe network is designed to deal with a 1 in 5-year rainfall event, and can manage around a 1 in 10-year event through secondary flow paths including flooding on roads. Where heavy rain coincides with a high tide, temporary pumps may be needed and are deployed in the locations in shown in figure 12 as necessary.

Stormwater ponds at the end of Blake Street were built in 2014/2015 by SCIRT as part of a wider stormwater system including a pump station, designed to discharge stormwater into the estuary at all tide levels. The work also included a stormwater pipe network involving a large chamber and outlets, and an overland flow path.


Wastewater

The SCIRT programme introduced the use of pressure and vacuum sewer systems to improve resilience in areas with high risk of liquefaction, including across the Regeneration Strategy project area . The sewerage pipes run along Rocking Horse Road and spread out more extensively throughout South New Brighton with outflows at Penguin Street, Beatty Street, Kibblewhite Street, Admirals Way and the ocean outfall at Jellicoe Street. The ocean outfall takes the city’s treated wastewater from the oxidation ponds and transports it three kilometres out into Te Kaikai a Waro/Pegasus Bay. This was completed in December 2009 and cost $87 million.

Here's a map that shows the Council's stormwater and wastewater infrastructure in Southshore and South New Brighton.


Water Supply

The water supply for the Regeneration Strategy project area is fed from groundwater sources beneath Christchurch. The local pump stations are not subject to the temporary chlorination that much of the rest of the city is still experiencing, as the below-ground well heads have been checked and cleared of the risk for contamination. Water treatment by chlorination is not part of the long-term strategy for water supply as outlined in the Christchurch City Council 2018 Infrastructure Strategy.


Transport

Estuary Road, Union Street, Marine Parade (north of Bridge Street), and Rocking Horse Road (to the south of Caspian Street) provide the main transport routes within South New Brighton and Southshore. Bridge Street, including the Bridge Street Bridge, is classified as a minor arterial route in the Christchurch Transport Strategic Plan, highlighting its importance as the key connecting route to the rest of the city.


Why this is important

All infrastructure is vulnerable to the effects of climate change. Various upgrades following the earthquakes have improved the resilience of some systems, such as the wastewater, at least in the short to medium term. However, other systems, such as stormwater is highly vulnerable to the effects of climate change as the discharge points are often at the lowest elevation near the coast. These services are likely to experience increased failures and decreases in levels of service over the coming decades as sea level rises .

To date, responses to improve the resilience of infrastructure in the Regeneration Strategy project area have been ad hoc and reactionary, such as the response to the earthquakes, or individual flood events. The Regeneration Strategy provides an opportunity to take a strategic and adaptive approach to infrastructure management and investment that recognises future uncertainties, and the impacts of climate change.


What we don’t know

In its 30 Year Infrastructure Strategy 2018-2048, the Christchurch City Council has made no long-term commitments to defend areas and services from the effects of climate change. However, many asset management programmes now take climate change effects into account, such as design guidance for new infrastructure which adds allowances for increased rainfall intensity and sea level rise. The Council is also carefully considering how and when it constructs new infrastructure in areas affected by climate change.