A Wilderness of Urban Streams

Forest and Bird, Issue 314, 1 November 2004, Page 32

A Wilderness of Urban Streams

SARAH GIBBS;

Lying between two harbours, Auckland ts drained by 10,000 kilometres of streams.

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der the shade of a coastal broadleaf | | forest, a small stream drops over a waterfall and winds its way through a valley. The waters run slowly past the damp, fern-clad banks the stream has carved out of striated Waitemata sandstone. It is quiet except for the rustle of wind in the trees and the occasional tui call. Tonight glow-worms will adorn the banks like a mini galaxy hidden in the parataniwha. But today the sunlight trickling through the canopy reflects off the water and plays hopscotch on the vegetation along the banks. The tranquillity belies the fact that the road running down the adjacent ridge is one of the busiest residential roads in the country. You are in Le Roy’s Bush, a small reserve on the urban North Shore, and just minutes away is the bustling hub of New Zealand’s largest city. Ten thousand kilometres of streams run through the Auckland region. Many are short in length and less than two metres wide, which is hardly surprising given that Auckland straddles an isthmus. At least 11 of

New Zealand’s 27 species of native fish can be found in these urban streams, including the nationally endangered kokopu. In fact, some of Auckland’s urban streams are arguably in better health than watercourses in the intensively farmed South Island lowlands. The Le Roy’s stream is unusual in that a reasonable proportion of its catchment is protected — the legacy of a fundraising effort by North Shore Forest and Bird in the 1950s that resulted in the purchase of the valley for a public reserve. In terms of its ecological values it is like a multitude of other Auckland streams. Volunteers here, and on many other streams, are now revegetating riparian areas that used to be covered in South American pampas and other weeds. The Le Roy’s Bush restoration is part of Forest and Bird’s ‘Auckland Naturally’ project, One of the most widely known stream restoration groups in Auckland is also on the North Shore — the Kaipatiki Ecological Restoration Project. KERP’S volunteers work at revegetation, weed and predator control, rubbish clean ups and monitoring of stream water quality. The project also undertakes significant community education projects and has managed to attain sufficient funding to employ both a restoration co-ordinator and an education co-ordinator for several years. The Three Streams project in Albany, run by local identity John Hogan, has less focus

on community education, but provides an important bush area in a place earmarked as the new city centre of the North Shore by urban planners. Across on the southern shores of the Waitemata Harbour, Friends of the Whau was established as a group in 2000. The area has a significant place in Auckland’s history. Among other things, Maori used to paddle their canoes from the Waitemata Harbour through what is now the Pollen Island Marine Reserve, then up the Whau estuary and Wai Tahurangi (Avondale Stream) to portage across the isthmus to the Manukau Harbour. The growing Friends of the Whau group monitors water quality in the Wai Tahurangi and the Whau estuary. The group also undertakes regular cleanups and weeding, water monitoring for the Wai Care water project, education and advocacy. Last year alone members planted over 4000 trees in riparian areas. Replanting and rubbish cleanups go a long way towards decreasing erosion, stabilising water temperature and providing habitat, but do little to alleviate growing levels of water

pollution and increasingly erratic stream flows. They also do nothing to stop a growing number of headwaters being piped under new subdivisions and roads as the city grows. While the benefit of volunteer restoration projects to Auckland’s streams cannot be underestimated, the long-term health of these waterways is inextricably linked to stormwater quality and urban planning upstream and the health of the harbours downstream. tormwater is an increasing problem. Where rain used to soak into the ground where it fell, it now falls on an increasing number of roofs, driveways, roads, carparks and paved areas. On average in urban Auckland today, between 50 percent and 60 percent of residential areas are covered in impervious surfaces. That figure increases to between 70 percent and 90 percent in industrial areas. In the past, two thirds of rainfall would have soaked into the ground where it fell, with only one third running overground and into streams. Today those figures are reversed.

On a rainy day in Auckland, stormwater rushes across roads and down overloaded drains to the nearest stream. Several times each year there will be so much water in the stormwater system that it will overflow into the sewage system and cause that to overflow as well. When it enters a stream, the force and volume of the water often scours out the streambed it is entering, creating erosion. Naked soil on development sites is also washed down drains. The increased sediment load smothers aquatic species living in the receiving streams and ultimately washes out to sea to create the kind of muddy shores that foster a boom in mangrove populations. In some areas, increased development upstream (and the resulting increase in water running off from roofs, driveways and roads) has significantly reduced the period between major flood events downstream. In early May this year, a number of properties in the Henderson Valley that sit within what used to be a 100-year flood plain were badly flooded for the second time in five years. Many locals are, with some justification, blaming development upstream. Stopping growth in New Zealand’s largest city is unlikely to be either feasible or desirable, but there are ways the impacts of growth could be better managed. Riparian

areas can be protected and restored. Rain gardens, swales and innovative engineering designs can minimise runoff from impervious surfaces. Rainwater tanks can be installed to collect roof water for nonpotable uses, such as flushing toilets, thus reducing stormwater runoff from individual properties. Wetlands and stormwater detention ponds can reduce the levels of pollutants and sediment entering waterways from roads, carparks and development sites. Some of these measures are now being used. Stormwater detention ponds that reduce the amount of pollutants and sediment entering waterways are becoming standard practice. But planning and other non-engineering measures are generally being implemented only on an ad hoc basis. There is a huge variation in attitude towards the management of urban streams and things that impact on them between (and sometimes even within) the four territorial authorities that manage the most populated parts of Auckland. Waitakere City Council, for example, is attempting to integrate a "Green Network’ policy framework into urban planning, where waterways are protected as ‘green corridors’ for flora and fauna and as recreation areas for people. The council’s

‘Twin Streams’ project seeks to protect water quality, reduce flooding and erosion and promote public access to waterways in the Oratia and Opanuku catchments. Waitakere City Council also offers tangible support for volunteer groups wanting to restore stream corridors. Along with North Shore City Council, it also subsidises individuals installing rainwater tanks and provides information on other sustainable stormwater management practices. Manukau City Council is also undertaking some stream restoration and revegetation work, notably in the Puhinui Stream and Pakuranga Creek catchments. At the other end of the scale completely, possibly the last stream that ran unpiped from source to sea within Auckland City Council’s jurisdiction was piped last year to make way for a new roading project. The state of urban streams has wider implications than the local survival of native freshwater fish species and the health of riparian bush and birds. Sewage and polluted stormwater running into streams has led to North Shore City Council to issue health warnings advising people against swimming at their local beaches after heavy rain. Flooding occurs with increasing regularity. A Waitakere City Council report calculated the cost to the Auckland region of allowing continued deterioration of harbour quality, through stormwater pollution, to be between $118 million to $150 million annually. With the preservation of rivers and their margins listed in planning law as ‘a matter of national importance; it is a little curious that there are no national guidelines or measures to ensure this is done. This is particularly so with cumulative problems that require widespread and long-term planning

measures. People could ask, for example, why the Building Act is not amended to require all new houses in urban areas to install rainwater tanks to catch roof water to use for flushing toilets, watering the garden and doing laundry, in the same way that the Act requires all new houses to be insulated? This would not only help protect urban streams from increased stormwater runoff, but also stop water taken from the Waikato River being literally flushed down Auckland’s toilets. Local authorities acting individually cannot address a problem on this scale. In general, however, we now have the ability to improve the health of our urban streams and the harbours they flow into. Factors contributing to the degradation of urban streams are now not only being identified; some of the solutions are starting to be incorporated as standard planning and engineering practice by some councils. Each one of us now has the opportunity to enjoy, even help restore, a local stream. We can also easily take a break from the city within our cities; and watch reflected light dance on damp ferns as inanga slide into the shadows of deep pools and tui sing above our heads. — SARAH GIBBS was formerly a Forest and Bird field officer in Auckland.