Mapua/Ruby Bay is a growing township of approximately 2,200 residents and is located 19kms west of Richmond. Ruby Bay area is a coastal strip with relatively recent developed land with a piped network and stormwater detention systems. Mapua is a mixture of urban and semi-urban development with the majority of stormwater from earlier developments going to soakage. Only the more recent developments have included piped stormwater systems, which mostly discharge into open drains and into the Mapua estuary. A tidal gate at the end of the Aranui Road stormwater pipe protects the reticulated piped system from high tide backing up into the system. The catchment upstream of the Coastal Highway and Stafford Drive drains out through the Seaton Valley Stream. This passes through a culvert under Stafford Drive and discharges into the Toru Street inner estuary further downstream. The area draining into the Seaton Valley Stream accounts for 65% of the Mapua/Ruby Bay drainage area.
The lower portion of Seaton valley catchment is vulnerable to flooding in large events. Generally, the stormwater network operates well but there are capacity issues at the bottom end of Seaton valley Stream.
Council has already completed the first stages of upgrading the drain, and plant to complete the final stage in 2023/24. In addition, works are planned for the Stafford Drive Stormwater Pipe Extension to increase capacity of secondary flow paths and prevent local flooding issues.
Figure 11: Mapua / Ruby Bay Urban Drainage Area and Drainage Network 3.6.1 District Plan Notations
The Tasman Resource Management Plan (TRMP) contains the following notations for the site:
Planning Map: Numbers 54, 86, and 87 Mapua / Ruby Bay
Zoning: The Mapua / Ruby Bay UDA contains the following zones:
Commercial Residential Coastal Rural 2
Conservation Rural 1 Rural 3
Light Industrial Rural 1 Closed Rural Residential
Open Space Rural 1 Coastal Rural Residential Serviced
Recreation Rural 1 deferred Light Industrial Rural Residential deferred Residential
Residential Rural 1 deferred Residential Tourist Services Residential Closed Rural 1 deferred Rural
Residential Serviced Table 12: Mapua/Ruby Bay Zones
Stormwater Designations: None
3.6.2 Land Uses within and adjacent to the UDA
The Mapua UDA is quite broad and covers many land uses. The main Mapua township predominantly consists of residential uses with relatively small commercial areas within the town and at the wharf. There are very few industrial or mixed business style land uses. There is a further area of residential use along the Ruby Bay coast and on the hill slopes above this. The majority of the UDA area consists of rural and rural residential land uses. Residential scale housing is spreading into these areas in places. There is some isolated forestry that has been felled in recent years. There is also assorted smaller scale horticultural uses in places.
Land uses adjacent to the UDA are mainly rural in nature but do include a number of areas of rural residential uses.
3.6.3 Topography
Mapua consists of flatter, to rolling hill country in and around the main township. The Ruby Bay coast is flat near the coast and subject to coastal inundation during storm events. This area also characterised by the coastal escarpments above the road. Moving inland is the main Seaton Valley with flat land on the valley floor. Above this and throughout the inland portion of the UDA are many low hills and gullies in a quite complex area of topography.
3.6.4 Soil Types and Permeability
The soil types in Mapua / Ruby Bay range from sand to loam to hill soils with permeability from rapid to moderate/slow. The hill areas of the Mapua soil series is identified as having a medium to high level of erodibility, as does the coastal area from Broadsea Ave to the Leisure Park. Other areas do not have erosion identified as a soils limitation. Specific descriptions and permeability are shown in the table below.
A map series showing their location is included within Appendix B.
Soil Series Soil Type Permeability
Tahunanui Sand Rapid
Braeburn Clay loam Moderate/Slow
Mapua Hill Soils and Sandy Loam Moderate/Slow
Table 13: Mapua/Ruby Bay Soils
3.6.5 Surface Water and Receiving Environment
The Seaton Valley Stream is the main drainage through the Mapua UDA. It flows out of the hills and gullies in Seaton Valley through the back of the main Mapua township and into an arm of the Waimea Inlet near Toru Street. Other surface water drainage is of a more minor scale with most stormwater flowing directly to Tasman Bay along the Ruby Bay coast. The receiving environment therefore consists of the Seaton Valley
amenity values and recreational values for swimming, boating and fishing. All water has cultural values to Māori.
3.6.6 Drinking Water and Soakage to Ground
Mapua/Ruby Bay sources its drinking water from the Waimea Bores, via the Waimea Water Treatment Plant which chlorinates the supply. In the case of the Mapua Rise area (area of newer development off Mapua Drive and Higgs Road intersection) water is sourced from deep bores. These bores are located near Mapua Drive and are between 120m and 350m deep. The bores are within the UDA boundaries. Soakage to ground is a feature of the stormwater network in Mapua / Ruby Bay however these are remote from the identified bores. The soakpits are primarily located in the Tahunanui soil series.