Preliminary review of coastal processes and hazards for multiple sites along various shorelines of South East Asia countries.
A classifi cation system was developed that identified possible current and future hazards that had the potential to limit use or development of the sites. A screening level hazard assessment identified that while the sites are reasonably secure from direct effects of coastal erosion, there are some potential hazards associated with the sites that could limit development.
Environment Waikato identified the West Coast region as an area where there is little knowledge of coastal processes and associated hazards. Tonkin & Taylor compiled a team of experts to assess the state of knowledge available on the West Coast. Liaison with district councils identified priority areas in need of further investigation. This project forms a basis for future coastal hazard assessments along the open coast and within estuaries.
Coastal hazard mitigation and management is crucial in terms of coastal planning and development. Tonkin & Taylor provide specialist support to public and private clients requiring coastal hazard management at site specific or region wide scales.
Tonkin & Taylor provided a coastal hazard assessment with regard to a proposed development. The spit at Port Waikato has prograded significantly since 1853 due to a number of factors. Analysis of shoreline positions, river dynamics, sediment transport and climate change was undertaken. An assessment of future potential risk to the development from coastal and river processes was provided.
Cliff Street, Raglan - Coastal Erosion Prevention Works
Client : Waikato District Council.
Discipline : Coastal
Design and construction of erosion protection works along a section of shoreline fronting Cliff Street in Raglan which had undergone active erosion, resulting in loss of reserve and the undercutting of Pohutukawa trees. The construction included a tipped rock revetment along the base of the cliff, incorporating a timber boardwalk along the top and associated access stairs and ramps. The design and construction methods where developed to avoid any adverse effects on the coastal marine environment and to ensure consent compliance during construction. The locally sourced paddock boulders, timber boardwalk and coastal native planting will help to maintain the sites natural appeal.
The Orakei Marina is a 170 berth marina constructed on the western side of the Okahu Bay boat maintenance facility on the Waitemata Harbour. Dredging of approximately 140,000 cubic metres of sands and sandstone material was required along with construction of two breakwaters totalling 550 metres in length. Breakwaters consisted of dredged sandstone as the core material and were armoured with two layers of basalt rock armour. Marina parking areas were provided on a concrete wharf structure and paving and servicing existing land. All stormwater was treated prior to discharge.
Development within the Auckland Region has
tended to concentrate along the coast with
development often occurring close to the edge of
eroding sedimentary cliffs and on sensitive beach
systems. As a result
there are significant parts of the region’s coastline
that are exposed to coastal hazards. T&T
completed an assessment of coastal erosion hazard
covering over 2,400 km of cliff and beach coastline
within the Auckland Region. Past experience
deriving coastal erosion hazards at a number
of locations around the Auckland region was
supplemented with site specific and broad-scale
aerial assessment resulting in new techniques for
delineating erosion hazard being developed.
Regional coastal hazard study extending along
315 km of the Hawke’s Bay coastline.
The assessment was undertaken in the context
of managing increasing development pressure
in the coastal environment while considering
existing development and coastal erosion
issues. The project included coastal process
assessment, quantification of climate change
impacts, delineation of erosion risk zones for
33 settlements and towns and development of
regional scale coastal management strategies.
Tonkin & Taylor was engaged by Auckland City Council to
obtain all necessary resource consents for the restoration
of Kohimarama Beach. Kohimarama is one
of Auckland’s most popular beaches, and since the 1930s,
had lost most of its sand due to stormwater discharges
from the catchment behind the beach, and wave reflection
from the Tamaki Drive seawall.
Preliminary and detailed design of the $7.5 million
Oriental Bay foreshore development within the
Wellington harbour. The project included the
placement of 22,000 tonnes of sand to form a
600 m
long beach, construction of a submerged breakwater,
headland controls, pier, emerged breakwater and
submarine stormwater outfalls. The beach has
been an enormous success. In May 2004 it received
the coveted Supreme Award from the New Zealand
Institute of Landscape Architects. The following
month it won the 2004 NZ Institute of Architects
New Zealand Award in the Urban Design category.
Coastal inundation including climate change
effects is crucial for council management and
planning of development. Offshore extreme
wave climate was modelled using the numerical
package SWAN and the resulting extreme water
levels were assessed for 1% and 2% Annual
Exceedance Probability events at 20 development
areas between Pakiri and Karepiro Bay. The
results of the study assisted Rodney District
Council in setting building floor levels for future
coastal developments.
The Wairoa River Canal Waterway Development is a
279 lot canal village subdivision adjacent to the lower
reaches of the Wairoa River. The scheme involves
4.5 km of canal covering 22 hectares and is intended
to accommodate powerboats up to 20 m in length and
yachts up to 10 m in length. The scheme includes a weir
to control water levels within the canal system and
navigation lock. Following on from past work on the
Whitianga and Whangarei waterway developments,
Tonkin & Taylor provided a technical study of coastal
issues associated with the development in support of
an assessment of environmental effects. Three
dimensional hydrodynamic, water quality and
sedimentation modelling was undertaken enabling
refinement of canal design to achieve best practice
environmental standards.
Technical investigation of coastal erosion along
4 km of shoreline within the Manukau Harbour.
The study focused on reducing the erosion hazard
risk to Council assets and private property through
the formulation and implementation of management
strategies. The project included detailed design
and construction of new seawalls, low crested
breakwaters with planting, beach replenishment,
stormwater outfalls upgrades and slope
management.
Client : Environment Asia Sdn Bhd on behalf of Port Klang
Authority Sbn Bhd
Discipline : Coastal
Detailed design and assessment of environmental
effects for a
4 km port and wharf extension at
West Port within Port Klang, Malaysia. The project
includes the construction of 8 new container
terminals, reclamation of low-lying land and
capital dredging. The project site is located in the
Klang river delta, an area of high sedimentation.
Due to the location and scale of the development
a detailed assessment of existing processes and
potential physical effects was required.
