The Ashley-Rakahuri is a medium-sized braided river located in North Canterbury.
From the Ashley Gorge, the river flows east and enters the sea about 25 km north of Christchurch. In contrast to the larger snow-fed rivers, the Ashley-Rakahuri is fed by rainfall from the foothills and has relatively low flow rates.
The core riverbed study area consists of an 18km stretch of riverbed, extending from the confluence of the Okuku River down to the State Highway 1 road bridge.
The shorebird values of the Ashley-Rakahuri are well-recognised. The river and estuary are included in a list of wetland sites which meet criteria prescribed to be of international importance by the International Union for the Conservation of Nature (IUCN).
Following surveys of Canterbury rivers in the 1970s and early 1980s, the New Zealand Wildlife Service ranked their wildlife and conservation values; the Ashley-Rakahuri was one of five rivers given the highest possible ranking of ‘Outstanding’. However, declining bird numbers over the last 25 years have led to a more recent classification of ‘national’ importance.
Below SH1, the Ashley-Rakahuri River is tidal, and in combination with the mouth of the Saltwater Creek, forms an estuary containing over 150 ha of mudflats and shallow water, which is excellent feeding habitat for shore birds. It is a common stop-over site for birds migrating up and down the coast, as well as a handy feeding area for birds nesting on the river.
DOC’s Conservation Management Strategy for Canterbury 2014-2024 states that “Braided rivers are a defining feature of the Canterbury landscape”. This is endorsed by the fact that they are rare in the rest of the world, with New Zealand considered a hot-spot, and Canterbury the centre of that, with 59% of the country’s braided river surface area.
If there is one word which particularly defines braided rivers, it is the word ‘dynamic’.
Their constantly changing environment has given rise to a unique ecosystem of plants, animals and invertebrates, with the most obvious component being the birds - some of which depend largely or entirely on braided rivers for their survival.
Away from the coast (and a few wetlands), braided riverbeds hold the only remnants of the original plains ecosystems which are still reasonably intact. However their ecological values are increasingly threatened; most have been invaded by weeds and introduced mammalian predators, and are further degraded by a wide variety of human activities.
All photos by ARRG members - Lynley Cook, John Dowding and Nick Ledgard