Reanimating the strangled rivers of Aotearoa New Zealand

Abstract

Contemporary management practices have artificially confined (strangled) river systems in Aotearoa New Zealand to support intensified land use in riparian areas. These practices work against nature, diminishing the functionality and biodiversity values of living rivers, and associated socio-cultural relations with rivers. River confinement can accentuate flood risk by promoting development in vulnerable locations and limiting the flexibility to adapt to changing climate, prospectively accentuating future disasters. To date, uptake of space-tomove management interventions that seek to address such shortcomings is yet to happen in Aotearoa New Zealand. This is despite the fact that such practices directly align with M aori (indigenous) conceptualizations of rivers as indivisible, living entities. Treaty of Waitangi obligations that assert M aori rights alongside colonial rights of a settler society provide an additional driver for uptake of space-to-move initiatives. This article outlines a biophysical prioritization framework to support the development and roll out of space-to-move interventions in ways that work with the character, behavior, condition, and evolutionary trajectory (recovery potential) of each river system in Aotearoa.

Managing at source and at scale: The use of geomorphic river stories to support rehabilitation of Anthropocene riverscapes in the East Coast Region of Aotearoa New Zealand

“…Management of connectivity in this catchment is multi-centennial in scope. Adopting erodible corridor concepts and managing adjacent land tenure and land use is needed to accommodate the ongoing high rates of sediment supply to the lower Waipaoa as the channel continues to adjust to ongoing sediment influx in the coming decades (Brierley et al, 2023). Although gravel extraction could support management of aggrading reaches if carried out carefully and managed in an adaptive manner, in this instance the poor quality of the weak shales and sandstones comprising the bulk of the Waipaoa bedload means this is unviable, and bedload yields are just ~1% of the suspended load (Gomez et al, 2001).…”

New Zealand's braided rivers: The land the law forgot

“…Despite the documented values and loss of braided river ecosystems, agricultural and peri-urban encroachment continues to operate across New Zealand like a ratchet because hard stopbanks (artificial levees) or bioengineered vegetated river boundaries follow the migrating channels inwards from either flank but do not retreat (Brierley et al, 2023;Figures 3-5). Braided rivers' declining capacity to adjust has broad-reaching consequences in economic, ecological and cultural dimensions, including the following:…”

“…• Habitat loss for threatened and endemic species, altered biophysical connectivity (longitudinal, lateral, vertical) and biodiversity loss (Gray et al, 2018;Stanford & Ward, 1993;Wohl et al, 2019) • Loss of natural character of braided rivers (Brierley et al, 2023) • Reduced capacity for groundwater recharge (Wohling et al, 2018) • Reduced flood conveyance (Gluckman et al, 2017) • Increased erosion risk (Piégay et al, 2009) • Implications for indigenous M aori relationship with waterbodies (Hikuroa et al, 2021).…”

“…Despite the documented values and loss of braided river ecosystems, agricultural and peri‐urban encroachment continues to operate across New Zealand like a ratchet because hard stopbanks (artificial levees) or bioengineered vegetated river boundaries follow the migrating channels inwards from either flank but do not retreat (Brierley et al, 2023; Figures 3–5). Braided rivers' declining capacity to adjust has broad‐reaching consequences in economic, ecological and cultural dimensions, including the following: Habitat loss for threatened and endemic species, altered biophysical connectivity (longitudinal, lateral, vertical) and biodiversity loss (Gray et al, 2018; Stanford & Ward, 1993; Wohl et al, 2019) Loss of natural character of braided rivers (Brierley et al, 2023) Reduced capacity for groundwater recharge (Wohling et al, 2018) Reduced flood conveyance (Gluckman et al, 2017) Increased erosion risk (Piégay et al, 2009) Implications for indigenous Māori relationship with waterbodies (Hikuroa et al, 2021). …”

“…(b) Over time and at different flow stages, channels shift as the river reworks the various surfaces of the braidplain, maintaining the diversity of surfaces of varying ages that support biodiversity. (c) Land use intensification on areas of dry riverbed, often supported by stopbanks (artificial levees) or bioengineered willow river boundaries, constrains the range of variability of the river and intensifies stream power at higher flow stages within the narrower active channel zone (Brierley et al, 2023). [Colour figure can be viewed at wileyonlinelibrary.com]…”