Truths of the Riverscape: Moving beyond command-and-control to geomorphologically informed nature-based river management

Abstract

Truths of the Riverscape refer to the use of geomorphological principles to inform sustainable approaches to nature-based river management. Across much of the world a command-and-control philosophy continues to assert human authority over rivers. Tasked to treat rivers as stable and predictable entities, engineers have ‘fixed rivers in place’ and ‘locked them in time’. Unsustainable outcomes ensue. Legacy effects and path dependencies of silenced and strangled (zombified) rivers are difficult and increasingly expensive to address. Nature fights back, and eventually it wins, with disastrous consequences for the environment, society, culture and the economy. The failure to meet the transformative potential of nature-based applications is expressed here as a disregard for ‘Truths of the Riverscape’. The first truth emphasises the imperative to respect diversity, protecting and/or enhancing the distinctive values and attributes of each and every river. A cross-scalar (nested hierarchical) lens underpins practices that ‘know your catchment’. The second truth envisages management practices that work with processes, interpreting the behaviour of each river. This recognises that erosion and deposition are intrinsic functions of a healthy living river—in appropriate places, at appropriate rates. This premise underpins the third truth, assess river condition, highlighting the importance of what to measure and what to measure against in approaches that address the causes rather than the symptoms of unexpected river adjustment. The fourth truth interprets evolutionary trajectory to determine what is realistically achievable in the management of a given river system. Analysis of whether the river sits on a degradation or recovery pathway (i.e., condition is deteriorating or improving), alongside assessment of catchment-specific recovery potential, is used to foresight river futures. Viewed collectively, Truths of the Riverscape provide a coherent platform to develop and apply proactive and precautionary catchment management plans that address concerns for biodiversity loss and climate change adaptation.

Reanimating the strangled rivers of Aotearoa New Zealand

“…Active and continuous intervention is required to maintain flood capacity, yet equivalent outcomes could be achieved by simply giving the river more space, and allowing channels to adjust. As disturbance‐driven entities, naturally unconfined and free‐flowing rivers continuously adjust their form to variations in the flow of water and sediment, and changes in local or regional base level (Brierley & Fryirs, 2022). Working against nature does not work (Fryirs & Brierley, 2021; Newson, 2021).…”

“…Thankfully, design criteria are increasingly in‐hand to support such rewilding ventures (e.g., Ciotti et al, 2021; Wheaton et al, 2019). Appropriate management practices are fit‐for‐purpose, working with the river both individually and collectively (Brierley & Fryirs, 2022). Carefully targeted interventions for larger braided rivers, with their characteristic heterogeneity and biodiversity, are likely to have a high payoff for all the measures of impact/success indicated in Table 1.…”

“…Ashburton and Waiohine have a 10 m range (± 5 m) and Tukituki has a 2.5 m range (+2 m, À0.5 m). White lines indicate stopbank locations or regional base level (Brierley & Fryirs, 2022). Working against nature does not work (Fryirs & Brierley, 2021;Newson, 2021).…”

“…Command‐and‐control management practices seek to tame dynamic rivers (Holling & Meffe, 1996), but in so doing they restrict the capacity of a river to adjust, regenerate and recover (Brierley & Fryirs, 2022; Florsheim et al, 2008; Fryirs & Brierley, 2016; Kondolf, 2011; Piégay et al, 2005). Just as dams silence rivers (McCully, 1996), confinement between engineered flood and erosion defenses strangles rivers, locking channels in place and freezing them in time (Brierley et al, 2021; Kondolf, 2011).…”

“…Across the world, this orthodox logic and the underpinning social construction of values (Chan et al, 2016) is increasingly being challenged and tipped in favor of environmental rehabilitation. Innovative solutions that move beyond this pathology embrace proactive, precautionary, and preventative plans and restorative actions that address concerns for environmental protection and repair (Brierley & Fryirs, 2022). This is showcased, for example, by high‐profile dam removal interventions in the USA (e.g., Foley et al, 2017; Poff & Hart, 2002) and the advent of space‐to‐move river management programs in Europe (Buijse et al, 2002; Piégay et al, 2005) and North America (Biron et al, 2014).…”