Summary of report findings
Mairangi Bay Stream catchment has been largely developed to capacity since the mid 1900s and consists primarily of low density residential land use (76%). The Mairangi Bay Stream is a heavily modified stream with extensive lengths which have been culverted or lined. There is a low proportion of remaining open stream channel and retains little natural character. During summer, the stream experiences very shallow low flows during dry periods. The Mairangi Bay Stream discharges at the Mairangi Bay beach which is a popular beach for contact recreation.
| Length |
5.5km |
| Size of Catchment |
181.6 ha |
| Vegetation Cover |
11.8% (21.4 ha) |
| Imperviousness |
49.4% |
| District Plan Land Use |
Business |
1.2% |
| Recreation/Open space |
4.7% |
| Residential |
76% |
| Road |
17.5% |
| Recreational Use |
Low use except for stream mouth adjacent Mairangi Bay Beach |
| Receiving Environment |
Mairangi Bay, Hauraki Gulf |
| Substrate |
Artificial lining and silt/mud |
| Natural Wetlands |
Nil. |
| Artificial Wetlands |
1 |
| Periphyton |
Below nuisance levels. Some filamentous or diatomous algae occurred in open areas |
| Macrophytes |
Generally good with a few locations where there are possible management issues |
| Macroinvertebrates |
Moderate MCI score |
| Fish |
5 native fish species |
| Potential Man-Made Barriers to Fish Passage to Upstream Habitat |
16 (+ 4 natural barriers) |
| Channel Modification |
Heavily modified through out by culverting, piping and channel lining. |
| Erosion around Structures |
2 structures with moderate erosion and 3 structures with slight erosion |
| Bank Erosion |
Overall slight erosion through out. Moderate erosion along the lower portions of tributary 1 and 2. |
| Temperature |
18.1oC (measurements in autumn) |
| Suspended Solids, Turbidity And Visual Clarity |
Elevated suspended solids, high turbidity and poor clarity to other North Shore Streams |
| Oxygen and Oxygen Demand |
Oxygen low to moderate. Some organic pollution yet overall low oxygen demand. |
| Nutrients |
Typical concentrations compared to other North Shore streams. |
| Contaminants |
Limited information, but generally similar to other North Shore Streams. |
| Bacteria and Pathogens |
Levels of indicator bacteria indicate the stream is not suitable for contact recreation. |
| Sediment Quality |
No data. |
| Debris |
Some inorganic rubbish present. A few debris jam and log jams in stream |
| Stream Grouping |
Group 1, Stream Mouth |
0.1 km / 2% |
Group 2, High value
low disturbance |
0 km |
| Group 3A, Urban semimodified |
0.7 km / 12% |
Group 3B, Urban
modified |
1.1 km / 20% |
| Group 4, Concrete lined channel |
0.3 km / 5% |
| Group 5, Piped section |
3.3 km / 61% |
