What is included in the ‘Waihi Beach Coastal Protection’ project?
The Waihi Beach Coastal Protection project includes coastal and creek protection measures including:
- groynes at Three Mile Creek (Please see What are 'groynes' below)
- partial protection of the Waihi Beach shoreline through reconstruction and improvement of the existing rock revetment
- beach nourishment and dune enhancement
What does 'Coastal Protection' mean?
Coastal protection aims to protect against coastline erosion, which can have a damaging impact on 'housing' and 'infrastructure.
Coastal Protection techniques employed are either described as “hard” (e.g. groynes, rock revetment) or “soft” (e.g. beach nourishment, dune enhancement) techniques.
What are ‘groynes’?
Groynes are barriers or walls extending across the foreshore. They run perpendicular to the beach and support the build-up of sand around the groynes. This enhances the protection for the coast because the sand material filters and absorbs the wave energy. Many experts consider groynes to be a “soft” option because of the enhancement of the existing beach.
What is a ‘Rock Revetment’?
Rock Revetments consist of appropriately sized and placed rock along the foreshore parallel to the beach. Waves break against the revetment, which dissipate and absorb the energy. Water can filter through after the wave energy has been dissipated.
What does ‘Beach Nourishment or Dune Enhancement’ mean?
Beach Nourishment or Dune Enhancement physically rebuilds the sand dunes which would be further stabilised through appropriate planting of vegetation. Such a stabilisation does not disturb the coastline and creates a natural habitat. It’s important to note that , for dunes to be successfully established it generally takes a long period of time, and they need to be suitably located, i.e. above the high water line.
The coastal protection work is primarily designed to protect properties that are on or close to the beachfront. What will the rates impact of this work be on these properties?
The construction of the rock revetment will have a direct impact on 53 properties – rating impact per annum is estimated to be $1,200 - $1,400 per property.
The sand dune enhancement work will have a direct impact on 23 properties at the northern end of the Beach and 7 properties in Glen Isla place – rating impact per annum is estimated to be $400 - $600 per property.
The rating impact per annum for the ward is estimated to be between $9.00 - $11.00 plus GST per property.
How deep is the ‘Rock Revetment’ going?
The designed base level of the revetment is RL 0.0m in terms of Moturiki Datum. This level is based on modelling and physical surveying of the beach done by Environment Bay of Plenty. This data indicates the long term fluctuations in beach level. The revetment design has an additional level of conservatism.
What size rock is being used?
The rock being imported and placed along the Waihi Beach shoreline is between 0.8 and 1.2m in diameter.
Where is spare rock going?
The rock is being stored at a number of locations, including the Waihi Beach Quarry, Waihi Beach Wastewater Treatment Plant and Broadlands Block Reserve for re-use. The re-use may include landscape boulders or crushed to form aggregate to be used on path construction etc.
How is the geotextile fabric used?
The geotextile fabric is mainly placed beneath and behind the rock revetment. The fabric is there to prevent erosion of sand or fill from behind the rock revetment.
How high is the ‘Rock Revetment’?
The design height is 3.5m RL; determined from coastal modelling and physical measurement of the existing sand dunes fronting Waihi Beach. This height accounts for wave run-up during storm conditions.
Is the ‘Rock Revetment’ sufficient to handle a 50-year storm event?
The coastal erosion protection measures for Waihi Beach have been designed based on a 50-year return period storm event.
How close is the ‘Rock Revetment’ to beachfront property boundaries?
The location of the revetment in regard to property boundaries varies along the extent of the works. The location is constrained by limits imposed through the Environment Court Decision. For the properties fronting The Loop the revetment is located within the Reserve; however for sections of Shaw Road the revetment may partly be located within private property. The location of the revetment is designed to replace existing structures, within the same footprint, where practicable.
How wide is the top of the ‘Rock Revetment’?
The crest of the revetment is approximately 3.5m in width.
Are the voids between the rocks being filled?
The voids are created as a result of the rock used in construction of the revetment. The contractor is placing individual rocks to lock together as tightly as practicable. It is inevitable that there will be voids between the rocks with the size of the voids related to the rock size. The voids in the lower section of the revetment below beach level will be filled with sand. There is no point in filling the voids above beach level as wave action would remove the fill.
Will rocks shift with wave action?
The rock size and weight is designed to prevent movement of rocks during wave action. The rocks are carefully being placed to lock together as tightly as possible.
What goes along the top of the ‘Rock Revetment’?
The section fronting The Loop requires a public walkway to be constructed in the reserve area between the revetment and private property. The location and type has yet to be determined as we are waiting to see how the revetment finally fits with the reserve and what type of walkway would be best suited.
For the section fronting Shaw Road, no structure is proposed, however the top of the revetment will have the larger voids filled with appropriately sized rock to allow emergency access along the top of the revetment. The emergency walkway is to allow public who are caught on the beach to gain access to the next formal beach access.
How will the public access the beach after the ‘Rock Revetment’ is completed?
There are a number of formal access ways included in the works at the identified public access points. These are either timber stairs or ramps.
How will beachfront property owners access the beach?
Beachfront property owners fronting the revetment will be advised to use the public access points. For the properties fronting the beach nourishment section, informal beach access will be provided at locations to be confirmed.
Will special features such as extra access, boat ramps or other additional facilities along the ‘Rock Revetment’ area be allowed?
The works being undertaken are controlled by consent from the Environment Court and Environment Bay of Plenty. Should beachfront property owners wish to construct private structures, such as a boat ramp, then they will need to seek consents from Environment Bay of Plenty and Western Bay of Plenty District Council for this activity to occur.
What is happening with the Norfolk Pines?
Council will try to retain as many as possible. But where the roots interfere with the filter cloth the tree may need to be removed.
What are the plans for the ongoing maintenance of the ‘Rock Revetment’?
The revetment will be regularly monitored as required by the consent conditions. The monitoring will include a mixture of topographical survey and visual inspections by Council staff.
Is the cost of repairs factored into the overall cost?
Should maintenance to the structure be required, work will be undertaken by Council and funded by maintenance provisions. A small component of the yearly charge relates to such maintenance provisions.
What responsibilities do beachfront property owners have regarding the 'Rock Revetment’?
The revetment is a Council asset with an important function to prevent erosion. Beachfront property owners do not have responsibilities for maintaining the structure, and will not be permitted to modify the revetment in any way without consent from the district or regional council.
Will beachfront property owners be required to maintain their frontages with dune maintaining plants?
Planting above the revetment and along the beach nourishment section will be undertaken in collaboration with Bay of Plenty Coast Care, including public planting days. Council will work with Coast Care and beachfront property owners to establish and maintain the plants and avoid colonisation by exotic plant species. Beachfront property owners are encouraged to assist with maintaining any planting in front of their properties.
Will the remnants of previous retaining structures be removed in front of dune areas such as between Three Mile Creek and the new ‘Rock Revetment’?
The steel and timber retaining structure located between Three Mile Creek and the new revetment will be removed as part of the works. For the beach nourishment section, the steel and timber retaining structures will be removed and where appropriate suitable rock will be buried at the base of the existing dune.
How is Environment Bay of Plenty involved in this project?
EBOP is firstly involved by assisting in the dune enhancement, which will be done in close co-operation with Bay of Plenty Coast Care. Another involvement is the monitoring of the actual construction to make sure the works are within Resource Consent conditions. Therefore an EBOP Compliance Officer visits the site on a regular basis (weekly to fortnightly) to inspect the ongoing works.
What is the slope of the rock revetment?
The face of the revetment is inclined differently for The Loop and Shaw Road. For The Loop the face is a bit steeper (1:1.5) than along Shaw Road (1:2). Through that approach the revetment at The Loop requires a lesser area and leaves enough space at the rear for the emergency walkway.
Where can the public find information about the design?
Please go to the Quick Facts and Stats page for information and layout plans of the proposed design. However the opportunity also exists to visit the project site office to view the drawings and speak to the Project Manager.
Why is the rock revetment looking different to the diagrams shown to the public?
The revetment construction is being undertaken as per the drawings and diagrams shown to the public. However some differences may occur in the final look due simply to scale and actual construction constraints in a structure of this size.
Where can the public find information about 'Management Plans' and the 'Monitoring Programme' ?
This information as requried by resource consents, has been submitted to the Regional Council for technical approval. Any approved version of these plans and programme can be obtained directly from Environment Bay of Plenty http://www.envbop.govt.nz