THE COASTSTATE OF THE ENVIRONMENT

THE DISTRICT HAS 5SURF BREAKS OF NATIONAL

SIGNIFICANCE

THE GISBORNE DISTRICT HAS

712 KILOMETRES OF DIVERSE COASTLINE

COAST OF GISBORNE DISTRICT - TAIRĀWHITI

PRINCIPAL FINDINGS y 83.6% of all coastal water quality

samples taken between spring 2012 and the end of summer 2015 were in the “surveillance” (suitable for swimming) category. Only 1.3% of samples were in the “action” category.

y There have been 15 overflows from the sewer system into the city rivers in the last five years.

y Sand extracted for development works and construction has decreased over the three year period.

y In 2015 strong south-west wind and currents exposed prehistoric forests at a number of locations, along the coast. They were reburied by sand over the 2015/2016 summer.

y Coastal erosion continues at the end of Kaiti Beach Road, south of the Waipaoa River mouth near Te Wherowhero lagoon. There is periodic erosion at Wainui Beach from Tuahine Point groyne north to Stockroute, and also north of the Uawa River to the end of Banks Street.

y Coastal accretion is occurring north of the Waipaoa River mouth to Pacific Street. Other monitored coastlines are showing no significant trends of accretion or erosion.

y Recent work on updating natural coastal hazards has been completed with new maps prepared for coastal erosion, coastal flooding and tsunami hazards.

GISBORNE 2013-2015

Gisborne District has a diverse coastline stretching from the rocky basaltic headlands of Lottin Point in the north to the Wherowhero lagoon and coastal reef systems in the south. This diversity provides a wide variety of habitats including coastal cliffs, sandy beaches, extensive dune systems, rock platforms, and associated herb fields.Gisborne and the East Coast are renowned for our beautiful, golden and uncrowded beaches. Nationally significant surf breaks are located at Makorori Point - Centres, Wainui: Stock Route, Pines and Whales and the Island. Pouawa is the location of the Te Tapuwae o Rongokako Marine Reserve.The region’s geological history is plain to see in our many headlands with fractured and contorted layers of sedimentary rock.The range of habitats in the coastal environment support a diverse range of species ranging in size from microscopic animals in the sand and mud of our estuaries and beaches to dolphins, seals and orca who are regular residents of our coastal areas.

MARINE WILDLIFEEast Cape is an important migration landmark for several whale species – with southern right, humpbacks and sperm whales using East Cape to navigate along New Zealand’s East Coast. Gisborne waters also mark the north range of other species like dusky dolphins and leopard seals, which migrate north over winter. Our warmer waters are also a destination for migrating female southern right whales as they find their primary winter calving habitat in the waters between Mount Maunganui and Napier. The deeper waters along the Hikurangi Trough are also important feeding areas for many species.Our coastal waters are also a rich fishery with substantial commercial and recreational fisheries being supported. Species such as crayfish are iconic for the East Coast. Our coastal and estuarine areas in particular also support a wide range of native birds. Of particular significance are Te Wherowhero, Pouawa, Whangaokeno Island and Te Araroa coastal wetlands and lagoons.

Each year during spring and summer, Council monitors popular bathing beach sites for concentrations of faecal indicator bacteria. A high concentration of faecal indicator bacteria means that it is more likely that disease causing organisms are present. These can pose a health hazard for recreational activities such as swimming, surfing and other water contact activities. It does not mean that anyone swimming in the water at the time will actually be affected. Council uses the Ministry for the Environment guidelines for enterococci counts to assess bathing water quality.

Coastal water quality is monitored at 22 beach sites and five estuarine sites. Monitoring occurs weekly at 12 sites during the bathing season (November to March inclusive), fortnightly at a further nine coastal sites during this period, fortnightly through the year at Paouawa and Makorori surf breaks, and then monthly at 11 of these sites for the remainder of the year. Three sites at the top of the East Cape area (Lottin Point, Onepoto Bay and Te Araroa) are also sampled monthly December to February. Overall Gisborne bathing beach water quality results are very good. A high percentage of ‘Surveillance’ category results combined with low median enterococci counts indicates that the microbiological water quality of the regions bathing beaches is generally high.Of the 593 samples collected throughout the region between spring 2012 and the end of summer 2015, 90.3% of samples were below the ‘Action’ guideline – 83.6% of samples were suitable for swimming in that they were within the ‘Surveillance’ category and 15.1% were within the ‘Alert’ category. This indicates that under dry weather conditions the risk of becoming ill as a result of faecal contamination of sea water during water contact is very low. Only eight samples – 1.3 % were within the ‘Action’ category.

COASTAL WATER QUALITY IS MONITORED AT

BEACH SITES AND

ESTUARINE SITES

83.6% OF WATER SAMPLES WERE WITHIN THE SAFE SWIM CATEGORY WITH ONLY

1.3% IN THE PUBLIC HEALTH WARNING CATEGORY

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WATER QUALITY FOR RECREATION

In the event of an ‘Action’ category result public health warnings are issued by the council and signage is erected. In 2014/15 the Gisborne Recreational Beaches were graded Very Poor (Midway, Waikanae, Makorori settlement and Wainui beaches) to Good (Tokomaru Bay) against Ministry of Health/Ministry for the Environment guidelines. While the poorer graded beaches are still regarded as generally safe for swimming, there are periods when, due to high rainfall and stormwater runoff, levels of bacteria in the water exceed the single sample limit of 280 Enterococci per 100ml. For the city beaches, the urban streams and rivers are the likely source of contamination and the Waikanae Beach is the area most significantly affected.Water quality in our urban estuaries and lagoons - Turanganui, Waikanae, Taruheru, Waimata, Wainui Stream and Hamanatua Stream - is also monitored. All of these areas are influenced by urban and rural land uses, and water quality is frequently much poorer than in our coastal locations. The Wainui and Hamanatua Stream lagoons and the Waikanae Stream all frequently exceed safe swimming guidelines and people are not recommended to swim in these areas.

Some of the beach sites monitored are located close to stream or river mouths, which can be a source of contamination particularly after heavy rainfall. Birds can be the primary source of contamination as was highlighted in the 2014 bathing beach sampling period when the Makorori Settlement site was in the ‘Alert’ category for some time. A colony of shags was roosting in a dead tree above rock pools on the headland tidal action washed the contaminated water to the beach at the settlement.

Urban water quality is generally very poor and this affects the Waikanae and Midway Beaches in particular. Normal sources of bacteria include dogs and birds. During heavy rain events the sewer overflows into city streets when the amount of stormwater entering the system becomes too great for the size of the pipes. This leads to toilets being blocked and sewage overflowing over residential properties. To prevent contamination on the streets affecting thousands of residents, the scours are opened allowing stormwater and untreated sewage into the Taruheru, the Waimata and the Turanganui Rivers.

Between 2013 and 2015 83.6% of all bathing beach water samples were within the ‘Surveillance’ category of the Ministry for the Environment Guidelines 2003.

PERCENTAGE OF COASTAL WATER QUALITY SAMPLES BELOW ACTION GUIDELINE (280 cfu/100ml)

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WASTEWATER OVERFLOWS DUE TO HEAVY RAIN

Between 2011 and 2015 Council recorded 15 incidents relating to sewage overflows during heavy rain when the scours were opened.

While wet weather sewage overflows are a concern for water quality, the impacts of sewage overflows and spills during dry weather are much worse as the wastewater may not be washed down through the stream until rain occurs.

Council fined the Engineering and Works Department $50,000 for a dry weather discharge into the Wainui Stream in March 2015. This discharge had gone unnoticed and had already impacted the stream significantly when it was discovered. The effects on the environment were severe with dead eels found on the banks of the stream near the discharge. The Wainui Stream has very low flows during summer months and is adversely impacted by grazing stock and use as a dumping ground for organic matter (e.g. rotting fruit, lawn clippings). A study is underway to determine sources of contaminants and how water quality can be improved.

Discharges of wastewater to city rivers 2011 2012 2013 2014 2015

Number of events 4 events 5 events 2 events 3 events 1 event

MICROBIOLOGICAL WATER QUALITY GUIDELINESIndicator Surveillance Alert Action

Enterococci (cfu/100ml) No single sample >140 Single sample >140 Two consecutive single samples > 280

The Ministry for the Environment’s 2003 Microbiological Water Quality Guidelines provide guideline limits for enterococci for marine water contact recreation.

Good water quality is important for the health of marine and estuarine life as well as for recreational use by people. Coastal inshore waters near Gisborne City provide for a range of ecological, social, economic, cultural and recreational activities.

However these areas are also the receiving environments for the urban and industrial impacts within Gisborne City and rural impacts from land-based activities, and are susceptible to a number of water quality issues. Gisborne City’s roading and stormwater network are often directly connected to the city’s three rivers which all contribute to the transport of pollutants to the inshore waters of the marine environment.

Gisborne City’s wastewater is also currently discharged within Poverty Bay. However land based wastewater disposal options via treated wetlands are currently under investigation.

Contaminants found within city rivers and coastal environment can contain nutrients, sediments, bacteria, viruses and pathogens, hydrocarbons, and heavy metal compounds. These contaminants can have both chronic and acute effects on marine based species, and can consequently cause degradation of these ecosystems.

EFFECTS OF SEDIMENTATION

Our heavily eroding landscape means that our estuarine and coastal environments feel the strong effects of sedimentation, and most of our major river systems – Waipaoa, Turanganui, Pouawa, Waiomoko, Uawa, Waiapu and Awatere Rivers all discharge large amounts of sediment each year to the coast. The Waiapu River discharges the largest amount of sediment – 36 million tonnes each year, while the Waipaoa discharges 15 million tonnes of mud, silt and sand per year to Poverty Bay.

This large amount of sediment is greater than anything seen in any other part of New

EFFECTS OF NUTRIENTSEutrophication of estuarine waters can also affect the health of organisms in these waters. Estuaries are far more sensitive to stressors than open coastal environments. The largest estuary in the region is the barrier impounded Te Wherowhero Lagoon (around 160ha) formed from the old Waipaoa River mouth from which it is now cut off. All the other estuaries tend to be smaller and highly riverine in nature. Te Wherowhero Lagoon is subject to water quality impacts from mainly agricultural stressors with key issues around on sedimentation and eutrophication. Over the last 50 years the estuary has lost a lot of its former wetlands and has a number of drains and streams entering from agricultural land. These factors put the estuary at risk

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36 MILLION TONNES, THE LARGEST DISCHARGE OF SEDIMENT IN NEW ZEALAND

THE WAIPAOA DISCHARGES

4,100 TRUCK LOADS OF MUD, SILT AND SAND PER DAY

Zealand, and while our local marine life has had to adapt to this over the years, it does mean that many marine life-forms will live under permanent sedimentation stress. Very large pulses of sediments entering estuaries in flood events can bury estuarine organisms. Fine, silty sediments are generally rapidly discharged to the sea and become very widely dispersed by wave action and currents. During large flood events however sedimentation can be catastrophic for benthic organisms, and biodiversity may take many years to recover after very significant events.

of eutrophication with a slow build-up of nutrients in its water and sediment and associated macroalgal blooms.An ecological restoration project run by the community and interested parties was established in 2007 since then a large number of native plantings have been established. In 2015 Gisborne District Council commissioned Bay of Plenty Regional Council to assess the existing coastal environmental monitoring network and provide recommendations on future monitoring requirements. Additional monitoring is planned as a result to help track any changes associated with potential eutrophication. This will include components that specifically monitor any changes in macroalgal abundance and sediment changes.

THE WAIAPU DISCHARGES

WATER QUALITY FOR ENVIRONMENTAL HEALTH

DISSOLVED OXYGENLow dissolved oxygen concentrations have adverse effects on many aquatic organisms. It can also cause reducing conditions in sediments, so they release nutrients and toxicants to the water column where they may add to existing problems.The Australian and New Zealand Environment and Conservation Council (ANZECC) guidelines recommended that dissolved oxygen should not be permitted to fall below 6 g/m3 or 80-90% saturation, determined over at least one day-night cycle.Dissolved oxygen median values are considered to be poor in Taruheru River at Tuckers Road as they are below the 6 g/m3 ANZECC guideline value. In summer many of the estuarine areas are “saved by the tide” – as the cleaner coastal water comes into the

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2015 was marked by an unusual frequency of southwest swells which caused short term erosion of sand dunes and beaches around Poverty Bay and further north. As a result several ancient forests were exposed for the first time since 2008. These forests – located at Sponge Bay, Wainui Beach, Okitu, Waihau Bay and Pakarae are remnants of podocarp forests (rimu, matai and totara) that once existed on land which is now sea. They have been radiocarbon dated at 8000 -8500 years old according to Dr Chris Ward, the recently deceased former DOC East Coast/Hawkes Bay Conservancy Advisory Scientist. Tectonic movements and sea level rise drowned the forests and now only a few stumps in these locations remain. The forests grew on coastal

plains and estuary margins at a time when sea level was about 20m lower than today. This was during a pause in the generally rapid rise in sea level from 12,000 years ago at the end of the last ice age, when sea level was 120m lower than today, to the time when sea level reached roughly its present level 6500 years ago. Since then the landscape has been tectonically uplifted by roughly 20m in the 8000 years, so the forests are still close to sea level – a little above or below. The pause in sea level rise affected the ocean and coast all around the world at the time, but in most parts of the world any evidence of such events is submerged beneath the sea and buried in younger sediment.

estuaries and refreshes the oxygen levels, however the push of the coastal water up the Taruheru River is not sufficient to substantially improved dissolved oxygen levels as far as Tuckers Road – over 8km inland from the sea.

ANCIENT FORESTS ON OUR COAST

DISSOLVED OXYGEN MEDIAN VALUES 1980-2015

Ancient forest remnants on Wainui Beach(Photo: Chris Ward)

Turanganui River at the cut

Kopuawhakapata Stream at

Hirini Street

Taruheru River at Peel Street

Taruheru River at Wi Pere Bridge

Taruheru River at Tuckers Road

Waikanae Stream at Grey Street

Waimata River at Grant Road

Waikanae Stream at Stanley Road

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TESTING LOCATION

Woody debris on beaches is an increasing sight in much of the district as plantation forests planted after Cyclone Bola mature and are harvested. Slash and off-cuts from forestry contribute a large amount of debris to the beaches in flood and “fresh” events (a “fresh” is the first flood of the season, usually associated with large sediment and debris loads). Erosion of planted river-banks can also contribute woody debris to rivers, which is then transported to the beach. In the Poverty Bay area debris and other materials from within the Waipaoa, Waimata and Taruheru Catchments

There are currently 13 consents for sand extraction from the foreshore at the Navigation Beacon site, Centennial Marine Drive in Poverty Bay. These consents are typically granted for five years after which applicants are able to apply to renew their respective consents. Sand is mainly used for the construction industry. In 2015, just 8.3% of the 36,200 cubic meters of sand allocated was extracted. A total of 3020 cubic meters, 2236 cubic meters less than that extracted in 2014. The decline in sand abstraction rates over recent years reflects the general level of construction work underway in the city, with development in Gisborne City declining since 2012.

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Midway beach and small woody debris/mulch left from beach groomingWaikanae Beach, 21st September 2015

IN 2015 JUST 8.3% OF THE SAND

ALLOCATED WAS EXTRACTED

2236 CUBIC METRES LESS THAN 2014

make their way offshore and onto Paokahu, Waikanae, and Midway beaches. The September 21st, 2015 flood contributed a large quantity of debris to the beaches of Poverty Bay, with the clean-up taking a number of weeks. A survey of the woody debris was undertaken following this large storm event. Much of the debris came down the Waimata River, where substantial landslipping had occurred in the catchment. In this one storm 11,110m3 of wood was deposited on Poverty Bay beaches.

WOODY DEBRIS ON BEACHES

Sand extraction from the foreshore at the Navigation Beacon

SAND EXTRACTION

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Beach cross sectional surveys have been undertaken twice yearly to understand beaech volume changes at Poverty Bay, Kaiti Beach, Wainui Beach, and beaches in Tolaga Bay.

KAITI BEACHThe western portion of Kaiti Beach near the Eastland Port Log yard and Poverty Bay Yacht Club has no significant trend changes over the period 2000 -2015 in the beach cross sections. However further east towards the end of Kaiti Beach Road there has been a trend of erosion of the dune and consequently the end of Kaiti Beach Road.

POVERTY BAYThis area has been monitored since the year 2000. South of the Waipaoa River mouth near Te Wherowhero Lagoon there has been a trend towards erosion of the fore-dune over this time. North of the Waipaoa River mouth there has been a trend towards accretion of the fore-dune up to approximately Pacific Street. From Pacific Street north to Waikanae Beach the beach profile is neutral with no significant trends of accretion or erosion.

WAINUI BEACHWainui Beach is a particularly dynamic beach and has been monitored since 1977. The sand budget and beach level trends are dominated by storm events. However from Tuahine Point Beach groyne north to Stockroute there has been a trend of periodic erosion. North of Stockroute to Whales the beach profile is generally neutral with no significant trends.

TOLAGA BAYSouth of the Uawa River mouth near the Wharf there are no significant trends since the beach monitoring started in 1989. North of the river mouth up to approximately the end of Banks Street there has recently been significant erosion. North of the end of Banks Street there are no significant trends.

RATE OF EROSION AND ACCRETION

BEACH CROSS SECTIONS TOLAGA BAY SOLANDER AND FERNEAUX STREET INTERSECTION 1990-2016

BEACH CROSS SECTIONS WAINUI STOCKROUTE 1996 - 2016

BEACH CROSS SECTIONS END OF KAITI BEACH ROAD 2004-2016

BEACH CROSS SECTIONS ROBERTS ROAD 2004 -2015

COASTAL EROSIONThe position of the shoreline is constantly changing through coastal processes. Rapid erosion may be experienced during storms, often followed by slow rebuilding of the coastline by natural processes. However, climate change and sea level rise will exacerbate coastal erosion in the future and some areas may permanently retreat. The Council has detailed coastal erosion maps for its coastal communities, which are reviewed periodically. It also recently commissioned less detailed mapping for the remainder of the coastline. An example is shown below. Area potentially sensitive to coastal erosion by 2115, allowing for approximately 1m of sea level rise. Source: Tonkin and Taylor 30548.000, August 2015.

COASTAL FLOODINGWhen sea levels and waves are larger than normal during storms they have the potential to flood the land and cause damage to structures and property. Historically, coastal flooding has not been recognised as a major hazard in the region. However, sea level will significantly increase the frequency of coastal flooding events. A coastal flooding study was completed in 2015, that produced maps of the areas potentially exposed allowing for sea level rise, as shown in the following example for Tolaga Bay. Maximum depth of coastal flooding (above GVD26 Datum) with a 1% chance of occurring in any one year, allowing for 1m of sea level rise by 2115. Source: NIWA Project GDC15201

TSUNAMIThe Gisborne region is one of the region’s most affected by tsunami in New Zealand. It is located adjacent to the Hikurangi Subduction Margin, a significant source of earthquakes and tsunami. Tsunami generated in the Hikurangi Subduction Margin may arrive at our coastline in approximately ten minutes to half an hour. Tsunami generated from parts of Peru and Chile also contribute to the tsunami hazard to the region, but have much longer arrival times of over fourteen hours.GNS recently completed a study to map areas affected by tsunami in Poverty Bay and Wainui. An example of the results is shown right.Maximum depth of tsunami flooding (above ground level) with a 0.2% probability of occurring in any one year, allowing for 0.5m of sea level rise by 2065. Developed from the weighted average of six major contributors at this return period. Source: GNS Science Consultancy Report 2015/219, March 2016.

The Gisborne Region’s coastline is affected by coastal processes including erosion, flooding from the sea during storms and tsunami. Climate change and sea level rise is expected to exacerbate all of these coastal processes. The coast is also the location of many of the region’s larger communities, including Gisborne City, Tolaga Bay and Tokomaru Bay. The exposure of development to these coastal processes creates coastal hazards.

COASTAL HAZARDS