# Principles of Riverscape Health

Hayley Corrine Glassic, Robert Al-chokhachy, Joseph Wheaton, William W Macfarlane, Chris E Jordan, Brian Murphy, Scott Shahverdian, Stephen Bennett, Nicolaas Bouwes, Kirstie Fryirs, et al.

► To cite this version:

Hayley Corrine Glassic, Robert Al-chokhachy, Joseph Wheaton, William W Macfarlane, Chris E Jordan, et al.. Principles of Riverscape Health. Wiley Interdisciplinary Reviews: Water, 2025, 12 (4), pp.e70028. 10.1002/wat2.70028. hal-05380416

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OVERVIEW

OPEN ACCESS

# Principles of Riverscape Health

Hayley Corrine Glassic¹ ID | Robert Al-Chokhachy¹ | Joseph Wheaton² | William W. Macfarlane² |

Chris E. Jordan³ ID | Brian Murphy⁴ | Scott Shahverdian² | Stephen Bennett² | Nicolaas Bouwes² |

Kirstie Fryirs⁵ ID | Gary Brierley⁶ ID | Damion Ciotti⁷ | Philip Bailey⁸ | Karen Bartelt⁹ | Barbara Belletti¹⁰ | Simone Bizzi¹¹ |

James Brasington¹² ID | Reid Camp¹³ | Emily Fairfax¹⁴ | Jordan Gilbert² ID | Justin Jimenez¹⁵ | Jeremy Maestas¹⁶ |

Timmie Mandish¹⁷ | Amy McNamara¹⁸ | Scott Miller¹⁹ | Baptiste Morizot²⁰ | Mathias Perle²¹ | Hervé Piégay²² | Helen Reid²³ |

Lindsay V. Reynolds¹⁹ | W. Carl Saunders²⁴ | Alden Shallcross¹⁹ | Peter Skidmore²⁵ | Rose Smith²⁶ | Benoît Terrier²⁷ |

Gus Wathen²⁸ | Nick Weber²⁸

¹U.S. Geological Survey, Northern Rocky Mountain Science Center, Bozeman, Montana, USA | ²Department of Watershed Science, Utah State University, Logan, Utah, USA | ³Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, Newport, Oregon, USA | ⁴River Network, Boulder, Colorado, USA | ⁵School of Natural Sciences, Macquarie University, Sydney, Australia | ⁶School of Environment, the University of Auckland (Waipapa Taumata Rau), Auckland, New Zealand | ⁷Pacific Southwest Region, U.S. Fish and Wildlife Service, Auburn, California, USA | ⁸North Arrow Research Ltd., Vancouver, British Columbia, Canada | ⁹U.S. Geological Survey, Oregon Water Science Center, Portland, Oregon, USA | ¹⁰CNRS-EVS, University Jean-Monnet, University of Lyon, Saint-Etienne, France | ¹¹University of Padova, Padova, Italy | ¹²Waterways Centre, University of Canterbury, Christchurch, New Zealand | ¹³Snake River Salmon Recovery Board, Dayton, Washington, USA | ¹⁴Department of Geography, Environment, and Society and the Saint Anthony Falls Laboratory, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA | ¹⁵USDA Forest Service Northern Region, Missoula, Montana, USA | ¹⁶USDA Natural Resources Conservation Service, West National Technology Support Center, Portland, Oregon, USA | ¹⁷USDA Natural Resources Conservation Service, Western Region, Portland, Oregon, USA | ¹⁸Natural Resources Defense Council, New York, New York, USA | ¹⁹Bureau of Land Management, Denver, Colorado, USA | ²⁰Aix-Marseille Université, Marseille, France | ²¹Upper Deschutes Watershed Council, Bend, Oregon, USA | ²²CNRS, University of Lyon, Ecole Normale Supérieure de Lyon, Lyon, France | ²³Scottish Environment Protection Agency, Stirling, UK | ²⁴USDA Forest Service, PacFish/InFish Biological Opinion Effectiveness Monitoring Program, Ogden, Utah, USA | ²⁵Dipper Consulting, LLC, Bozeman, Montana, USA | ²⁶Sageland Collaborative, Salt Lake City, Utah, USA | ²⁷Agence de l'eau Rhône Méditerranée Corse, Lyon, France | ²⁸Anabranch Solutions, Logan, Utah, USA

**Correspondence:** Hayley Corrine Glassic (hglassic@usgs.gov)

**Received:** 10 December 2024 | **Revised:** 15 April 2025 | **Accepted:** 8 June 2025

**Associate Editor:** Christian Torgersen | **Senior Editor:** Jan Seibert | **Editor-in-Chief:** Wendy Jepson

**Funding:** This work was made possible with generous support through cooperative agreements between Utah State University (PI Wheaton) and the Bureau of Land Management (L24ASS00310 and L22AC00247), the Natural Resources Conservation Service (NR203A750023C014, NR213A750023C005, and NR220436XXXXC007), as well as NASA (80NSSC21K1353). J.W. was supported by a Fellowship with the Collegium de Lyon and financial support from H2O'Lyon that led to the refinement of these principles and relaunch of the Riverscapes Consortium (https://riverscapes.net) focused on healthy riverscapes for all.

**Keywords:** biogeomorphic | hydrologic | resilience | sediment | vegetation regimes

## ABSTRACT

Riverscapes are the integration of terrestrial and aquatic systems from headwaters to estuaries that provide habitat and ecosystem benefits when in good health. However, current riverscape degradation is pervasive, impairing the function and resulting benefits of these systems. Healthy riverscapes are adaptive and some can ‘heal’ after disturbance with minimal to no human assistance. As riverscape health is threatened, a need exists to address current degradation and understand the potential for riverscape restoration—concisely communicating what comprises healthy riverscapes is essential to direct limited resources and increase efficacy of restoration and conservation efforts. Healthy riverscapes have (i) space to interact within their valley

This is an open access article under the terms of the [Creative Commons Attribution License](https://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

© 2025 Anabranch Solutions LLC and The Author(s). *WIREs Water* published by Wiley Periodicals LLC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
bottom; (ii) natural flow, sediment, and vegetation regimes appropriate to the biophysical setting and river type; and (iii) struc-
tural forcing to support diversity and that creates varied residence times for water, sediment, and vegetation. These three prin-
ciples are grounded in interdisciplinary science and lessons from riverscape scientists and restoration practitioners across the
world. Understanding the context, anthropogenic influences, boundary conditions, and legacy effects influencing riverscapes
is essential for the appropriate application of these principles in pursuit of achieving riverscape health. Emphasizing a holistic,
biogeomorphic view of riverscapes through these principles can guide policies, restoration actions, and monitoring frameworks
that ensure that riverscapes remain capable of accommodating and adjusting to disturbances while continuing to support biodi-
versity and human benefits.

This article is categorized under:

Water and Life > Conservation, Management, and Awareness

JEL Classification: Conservation, Management, and Awareness

1 | Introduction

At the interface of terrestrial and aquatic habitats, riverscapes have amplified importance in provisioning ecosystem benefits (Capon et al. 2013) and for providing critical habitat for multitudes of aquatic and terrestrial species (McKinstry et al. 2004; Richardson et al. 2010; Thomas 1979). However, the world's riverscapes are of poor health, threatening biodiversity, and human water security (Allan 2004; Tockner and Stanford 2002; Vörösmarty et al. 2010). Riverscapes, which include channels, riparian, wetland, flood-plain, and hyporheic habitats extending across dendritic networks from headwaters to estuaries, support a disproportionate amount of the Earth's biodiversity (Dudgeon et al. 2006; Reid et al. 2019). Riverscapes are also conduits for the movement of water, organisms, nutrients, wood, and sediment between aquatic and terrestrial habitats (Şekercioğlu et al. 2015) where populations and communities interact across spatial scales (i.e., geomorphic units to catchments; Brierley and Fryirs 2005; Hilty and Merenlender 2004; Rouquette et al. 2013; Tremblay and St. Clair 2011; Ward 1989; Wiens 2002). Humans are highly dependent on riverscapes (Brauman 2015; Cairns et al. 2024; Dunham et al. 2018; Flint et al. 2023; Hand et al. 2018), which provide ecosystem benefits such as freshwater for consumption, flood mitigation, carbon storage, support of agriculture and livestock production, and wildfire resilience (Fairfax et al. 2024; Fairfax and Whittle 2020). Humans also have strong cultural and spiritual connections to rivers and their health (Brierley 2020). In spite of these benefits, many riverscapes have been, and continue to be, compromised due to a variety of threats. This highlights the need to reinforce the value of and clearly articulate the components of a *healthy riverscape*, thereby providing a defensible basis for management, conservation, and restoration (called rehabilitation elsewhere; Fryirs 2024; e.g., Castro and Thorne 2019; Cluer and Thorne 2014; Wohl et al. 2005). Humans are influencing riverscapes both positively (i.e., through ecosystem-based restoration) and negatively (i.e., through valley bottom land uses, anthropogenic infrastructure, and command-and-control engineering or other actions that maintain “stasis”). This is occurring while riverscapes are simultaneously evolving, creating novel ecosystems (Morse et al. 2014), requiring a recalibration of perceptions and expectations of what a healthy riverscape is, and careful communication of this to stakeholders (Boyer et al. 2019; Fryirs 2024; Le Lay et al. 2013; Wyżga et al. 2009).

Our overview distills many convergent ideas from the scientific
literature on riverscapes into a set of three biogeomorphically

focused *principles of riverscape health* (adapted from Wheaton
et al. 2019). Despite the billions in currency spent on riverscape
restoration projects globally, the success of river restoration at a
scale needed to reverse degradation and mitigate more intense
anthropogenic and climate disturbances is questionable (Palmer
et al. 2010; Wohl et al. 2015). Significant gaps in the framing
of restoration goals and the limitations of current approaches
are evident (Beechie et al. 2010; Bernhardt and Palmer 2011;
Brierley and Fryirs 2022). Identifying the factors limiting riv-
erscape health is necessary so strategies can be developed and
enacted to better achieve restoration and riverscape manage-
ment goals at relevant scales in time and space (e.g., Van de
Bund et al. 2024). We consider a pragmatic definition of a riv-
erscape and propose three key principles of riverscape health
that all practitioners and managers could consider in-practice.
We elaborate on the theoretical, conceptual, and empirical bases
for these riverscape health principles with reference to support-
ing scientific literature and examples from a diversity of settings
and contexts. We then consider how different biogeomorphic
settings will affect landscape attributes that will change expec-
tations of how these principles should be applied. We close with
a discussion about the utility of such principles for developing
policies to guide riverscape management, monitoring status and
trend, and informing restoration objectives, project design, and
the efficacy of such actions.

2 | What Is a Riverscape?

The description of a *riverscape* can take on a variety of meanings and encompass physical, biological, and anthropogenic attributes (e.g., Carbonneau et al. 2012; Haslam 2008; Leopold and O’Brien Marchand 1968; Torgersen et al. 2022). Given our goal of condensing riverscape science into a working set of principles, we want to first constrain our scope of what a riverscape is using a definition focused on physical geography, appropriate for mapping, assessment, and monitoring, but that also includes the biological processes that build and maintain healthy, resilient riverscapes. The word “riverscape” in a scientific context was presented by Leopold and O’Brien Marchand (1968), later used by Ward (1998), and universalized through works such as Fausch et al. (2002), Allan (2004), Carbonneau et al. (2012), and Torgersen et al. (2022). The term “riverscape” is often invoked when talking about a “riverscapes approach”, wherein the term implies a holistic view of rivers at multiple scales, inclusive of
valley bottoms throughout a network. We therefore suggest a definition adapted from Wheaton et al. (2019) that sets the topographic constraints on the space that a riverscape occupies throughout a drainage network:

> Riverscapes are valley bottom networks of interconnected terrestrial and aquatic habitats, shaped by adjustments in surface and subsurface flow, sediment, and vegetation, that occupy the portion of the landscape that could plausibly flood under the contemporary, natural flow regime.

Additionally, we want to emphasize that use of the term natural is intended to be in context to regimes that could be returned or recreated within contemporary constraints or boundary conditions (e.g., simulating a flow regime through dam releases). Assessment of riverscape health must be considered in relation to 'expected' conditions before, during, and after disturbance events and in the context of altered boundary conditions (Brierley and Fryirs 2022; Fryirs 2024). Such definitions not only provide spatial clarity across the riverscapes network (Fausch et al. 2002; Torgersen et al. 2022), but emphasize the importance of structure and function, render practical utility in characterizing riverscape extents (i.e., valley bottom networks), and set realistic expectations about what can be achieved in management.

Riverscapes encompass more than the *currently* active channel(s) (Skidmore and Wheaton 2022; Stanford 2007; Stanford et al. 2017). In the simplest form, a riverscape includes the floodplain and channel(s) (i.e., valley bottom; Fryirs et al. 2016; Stanford 2007). However, this definition of places that could plausibly flood means that riverscapes can include both inactive valley bottom (i.e., those not regularly flooding but could plausibly flood under the contemporary flood regime), and lower lying areas (i.e., active valley bottoms that flood frequently; Ciotti et al. 2021; Croke et al. 2016). The entire valley bottom, by definition, might therefore support a mix of riparian vegetation, riverine wetlands, channel(s), and the space for channel adjustment and movement. Riverscapes are biogeomorphic systems driven by biological (growth and repair of vegetation; organic structures) and physical forces (sediment erosion, deposition, transport; Corenblit et al. 2007; Johnson et al. 2020). Wetlands, stream networks, and the hyporheos (where groundwater and surface water interact below the stream bed and in floodplains) must also be included (Skidmore and Wheaton 2022; Torgersen et al. 2022). Defining riverscapes involves acknowledging that they are shaped by variation and adjustment in physical and biological processes through space and time (Ward 1998) and are dynamic, interconnected habitats (Stanford et al. 2017) characterized by longitudinal, lateral, and vertical connections (Fryirs et al. 2007; Hynes 1975; Junk et al. 1989; Schlosser 1991; Stanford and Ward 1993; Vannote et al. 1980; Ward 1989). Connections created by the movement of water give riverscapes a network spatial structure (Carbonneau et al. 2012; Stanford et al. 2017; Ward 1998). Together, these characteristics create dynamic, interconnected habitats that rely on the presence of biology and disturbance regimes to promote and sustain a healthy riverscape.

## 3 | Why Riverscape Health?

We attempt to define riverscape health based on intrinsic value, boundary conditions, and context of individual riverscapes. Where riverscape health has departed from this potential, the recovery potential of riverscape health is based on societal and biophysical perceptions of environmental condition and value to humans (Blue 2018; Fryirs 2015; Hand et al. 2018; Tadaki et al. 2017). Recovery potential at its maximum is defined by the extent of the valley bottom being “active” (channels and floodplain), and when constrained by land use or infrastructure, is expressed as some proportion of the valley bottom (Wheaton et al. 2019). Healthy riverscapes are adaptive systems with biological, chemical, and physical processes that can capably recover from disturbances and require minimal to no external assistance to maintain biodiversity and ecosystem benefits (Angermeier and Karr 1994; Karr 1991, 1996, 1999; Morrison et al. 2023).

Many riverscapes are structurally altered as a result of the loss, limitation, or even over supply of sediment, vegetation (e.g., wood), and flow (Poff et al. 1997; Wohl et al. 2015). Numerous riverscapes have been severely regulated, where the natural movement of water, sediment, vegetation, and nutrients has been significantly altered (sometimes accelerated, sometimes decelerated). These alterations limit ecosystem benefits critical for terrestrial and aquatic wildlife and human populations (Biggs et al. 2015). For example, increases in water withdrawals and the presence of impoundments (e.g., dams and reservoirs) have altered hydrologic and sediment regimes (Dudgeon et al. 2006; Serra-Llobet et al. 2022; Vörösmarty et al. 2010). The alteration of vegetation regimes has also been extensive, often seen in the replacement of wooded landscapes with agricultural grasslands and direct removal of wood, beaver dams, and other vital structural elements (Bisson 1987; Wohl 2014), where structural elements are discrete objects that directly influence hydraulics (Wheaton et al. 2015). A reduction in the magnitude, spatial extent of inundation, duration of floods, and the elimination of some flows from the regime has altered stream power, sediment dynamics, and often the mobilization of wood. This typically constrains habitat variation via channel narrowing, channel incision (Morrison et al. 2023), reduced rates of channel meandering (Shields Jr et al. 2000), and loss of multiple channels or braiding (refer to Benke 1990; Grams et al. 2020). The simplification of channel form and process from the alteration of the natural flow and sediment regimes compromises riparian vegetation extent and diversity (Grill et al. 2019; Ligon et al. 1995; Poff et al. 1997), exacerbating the expansion of invasive riparian vegetation (e.g., Dean and Schmidt 2011; Shafroth et al. 2002; Stromberg et al. 2007; Wieting et al. 2023). Encroachment of invasive species (whether native or exotic) can also occur (e.g., conifers, Artemisia spp., Phalaris arundinacea) and further disrupt water, sediment, and structure (Manners et al. 2014; Scott et al. 2018). Additionally, natural resource extraction (e.g., timber harvest) and land use (e.g., agriculture, development, transportation; Fleischner 1994; Wisdom et al. 2005) have greatly reduced variation in riverscapes with cascading effects on water, sediment, and vegetation regimes (Allan 2004). Finally, many riverscapes have undergone profound and direct
<figure><img src="image_2.png" /></figure>

**FIGURE 1** | Examples of riverscape degradation in relation to the three principles: (a) a channel incised ~7m with limited space, access to the floodplain with an altered vegetation regime due to invasion by non-native vegetation and lack of wood and diversity in the active channel; (b) an engineered stream that has limited space to interact with the floodplain, with altered sediment regime due to riprap on banks and an altered vegetation regime and lack of in-channel wood because of vegetation removed in the floodplain; (c) a channelized, bound riverscape lacking space to interact with the floodplain, with altered hydrologic, sediment, and vegetation regimes due to a lack of diversity in the active channel; and (d) a simplified active channel lacking wood due to an altered vegetation regime (encroachment of upland vegetation due to lack of active channel interacting with floodplain) with an altered sediment regime resulting in loading of fine sediments into the active channel. Photographs used with permission from: (a) Nick Weber, Riverside Spatial; (b) Eddee Daniel, awealthofnature.org; (c) Brian Murphy, River Network; (d) Robert Al-Chokhachy, U.S. Geological Survey 2021.

modifications, fundamentally altering their shape and ability to adjust—including being straightened, fossilized by bank protection, and disconnected from floodplains by embankments (i.e., strangled rivers; Brierley et al. 2023, and engineering nature; Murphy 2024). The large effect of these alterations is inherent to the loss of key riverscape processes and is also reflected in the high proportion of riverscapes that are affected by such modifications (Belletti et al. 2020; Figure 1).

Given anticipated climate change threats (Wu et al. 2008) and the expansion of human populations and consumption, understanding the current extent of riverscape degradation may enhance the potential for riverscape restoration. Human encroachment (e.g., housing, agriculture, industrial development) and land use conversion (Theobald et al. 2020) within riverscapes limit transient water storage and groundwater-surface water interactions, increasing the susceptibility of communities to flooding (Skidmore and Wheaton 2022; Walz et al. 2019) and compromising the resilience of riverscapes and adjacent areas to droughts and fires (Fryirs et al. 2022; Jordan and Fairfax 2022). Furthermore, water demand and scarcity are expected to rise

(Mekonnen and Hoekstra 2016; Wu et al. 2008), highlighting the need to restore riverscape resilience and ecosystem processes (Brierley et al. 2023) to offset the increasing magnitude and frequency of droughts, fire, and flooding events (Fryirs et al. 2023; Serra-Llobet et al. 2022). Recognizing the limited resources to prioritize restoration actions (e.g., Agnew and Fryirs 2022; Glassic et al. 2024), more holistic and strategic thinking is required to increase the pace, scale, and efficacy of these actions. Succinctly communicating what composes a healthy riverscape is fundamental to moving forward with effective riverscape restoration.

4 | Riverscape Health Principles

We consider that riverscape health principles could act as the guidelines around which monitoring, restoration, and conservation can be structured. We anchor the riverscape health principles in the disciplines of ecology, hydraulics, geomorphology, hydrology, biology, and engineering (e.g., Brierley and Fryirs 2005; Johnson et al. 2020; Naiman et al. 2010; Roni
<figure><img src="image_3.png" /></figure>

**FIGURE 2** | Illustration of Principle 1—Riverscapes need space. Blue dashed lines approximate the valley bottom (VB) margin, the span of the active valley bottom is approximated with the white arrows, and the inactive floodplain colored transparent green. Healthy riverscapes have full access to these spaces (e.g., c and d), whereas many riverscapes no longer have full access to adjust or occupy their full riverscapes due to encroachment by land use and infrastructure (e.g., a and b). (a) The Clark Fork River demonstrates varying ability to adjust within valley bottom, with some space available for multiple channels to adjust (left section of image), and limited space through the urban bounds of Missoula (right section of image) where the river is constrained to one channel. (b) The Los Angeles River has been completely channelized through the city of Los Angeles and the channel has no space to move and does not interact with the floodplain. The channels of (c) Cooper Creek and (d) Zambezi River do have space for channel adjustment and are able to interact with the floodplain, producing multiple, anastomosed, and braided channels respectively. Google Earth satellite imagery of (a) Clark Fork of the Columbia River near Missoula, Montana, USA; (b) Los Angeles River near Los Angeles, California, USA; (c) Cooper Creek, central Australia; (d) Zambezi River near Leki, Luangwa District, Zambia.

and Beechie 2013). The principles are not only grounded in scientific reasoning, but have been refined from, and build off, nearly a century of lessons learned through restoration practice in various parts of the world (Beechie et al. 2010; Castro and Thorne 2019; Fryirs et al. 2021; Habersack and Piégay 2007; Palmer et al. 2005; Riquier et al. 2017; Tockner and Stanford 2002; Wohl et al. 2005).

Here, we distill riverscape health into three overarching principles:

1. Riverscapes need space.

2. Riverscapes need regimes (natural flow, sediment, and vegetation regimes).

3. Riverscapes need structural forcing to support diversity (of flow, sediment, and vegetation).

These principles could be used to identify what is currently lacking in a riverscape (what is no longer acceptable based on biogeomorphic conditions and societal values) or as a guide for what riverscape restoration could achieve. Below, we elaborate on the definition of each principle and support the principle with underlying science, and, where appropriate, provide visuals to demonstrate the principle “in situ.”

## 4.1 | Riverscapes Need Space

Healthy riverscapes are dynamic, regularly shifting the vertical and lateral position of channel(s) within their valley bottom, reworking, and potentially connecting with the floodplain.

Stream channel adjustment within the valley bottom is essential for maintaining functioning in many riverscapes (Morrison et al. 2023), including both lateral and vertical adjustments (Sholtes et al. 2018) that form, move, and maintain riverscape features at meso (reach; $10^2–10^3$m) and micro (geomorphic or habitat unit; $10^{-1}–10^1$m) scales. This concept of lateral adjustment, which includes processes such as migration and avulsion, has been described using many different phrases (e.g., “room for the river,” Baptist et al. 2004; “freedom space,” Biron et al. 2014; Malavoi et al. 1998; Terrier et al. 2016; “river corridor,” Kline and Cahoon 2010; “fluvial territory,” Ollero 2010; “erodible corridor,” Kondolf 2011; Piégay et al. 2005; refer to Biron et al. 2014 for a review of this concept). Conceptualizing lateral adjustment may be easiest in wide valley bottom riverscapes, where meso-scale channel features such as multi-threaded, possibly braided, large meanders, and active or abandoned channels exist (Figure 2).
The need for space is not limited to lateral channel adjustments across the valley bottom, as some riverscapes also need room to adjust vertically through aggradation and/or degradation. Healthy riverscapes are dynamic within natural capacities for adjustment (Brierley and Fryirs 2005); creating, moving, and maintaining a range of surfaces at a variety of elevations across the entire valley bottom (Sholtes et al. 2018). Processes such as pool scour and bar deposition are examples of geomorphic unit scale erosion and deposition, and incision or aggradation are the same processes acting at the reach scale (Brierley and Fryirs 2005, 2022; Wheaton et al. 2015). Bank erosion is a recurring process that provides a local sediment source (Trimble 1997) that creates, moves, and maintains riparian structure (Bayley 1991; Florsheim and Mount 2002; Junk et al. 1989), recruits nutrients for primary production, and maintains hyporheic flow paths that provide habitat and food for organisms (Wood and Armitage 1997). If space exists to move and adjust within the valley bottom, then healthy ecosystems, functioning riverscapes, and "shifting habitat mosaics" (i.e., temporal and spatial variation in riverscape characteristics and processes) can be maintained or enhanced where they have been lost (Stanford et al. 2005; Ward et al. 1999).

## 4.2 | Riverscapes Need Regimes

Riverscapes need natural flow, sediment, and vegetation regimes that are appropriate for their biophysical setting and river type, using energy to source and transport materials, resulting in channel variability.

Healthy riverscapes exhibit dramatically different distributions of fluxes of water and mass (e.g., sediment, wood, nutrients, etc.) transported with the water, in terms of direction and magnitude, from the geomorphic unit to catchment scales. Natural flow regimes are vital for the functioning of healthy riverscapes (Poff 2018; Poff et al. 1997). The magnitude, duration, timing, frequency, and rate of change of flow regulate physical and biological processes in riverscapes (Poff and Ward 1989; Richter et al. 1997; Walker et al. 1995), and, therefore, influence riverscape health (Poff and Ward 1989; Rosenberg et al. 2000). Physical processes shape habitats, and the movement of water (in time and space) within a natural flow regime organizes and defines riverscapes (Poff et al. 1997). The natural flow regime underpins riverscape health, governing other transport processes (e.g., sediment and vegetation) and regimes (e.g., thermal and nutrient; Olden and Naiman 2010; Van Cappellen and Maavara 2016). Recognizing how the temporal and spatial variability of flow regimes have been altered by anthropogenic disturbance and how they are "expected" to operate under these altered boundary conditions is necessary to determine which aspects of the flow regime can be managed within current boundary conditions.

Sediment regimes, which include the caliber and quantity of sediment being sourced, transported, and deposited, shape the physical structure of rivers (Wohl et al. 2015). In healthy riverscapes, inputs of sediments are an important driver for channel

adjustment, as the river can reshape itself producing habitat turnover and creation as it stores and transports new sediment. Specific sizes and ranges of sediment influence the life cycles of aquatic and riparian organisms (i.e., vegetation, benthic invertebrates, fishes, etc.; Poff 2018; Suttle et al. 2004; Wood and Armitage 1997). Organisms have adapted to sediment regimes (supply, transport, deposition, erosion), such that stages of development (e.g., riparian succession) or even predator-prey dynamics (Newcombe and MacDonald 1991) are contingent on the process. Because sediment regimes are diverse, resulting water quality related to sediment suspension and deposition varies seasonally and along the riverscape continuum (Fryirs and Brierley 2012; Vercruysse et al. 2017). Recognizing the variability of sediment regimes temporally and spatially, how they have been anthropogenically altered, and performance expectations are necessary for determining which aspects of the sediment regime can be realistically managed (Poepl et al. 2020; Wohl et al. 2015).

Vegetation regimes are a cycle of organisms contributing to riverscape processes through the continual input of energy, even after death. The physical template of the riverscape both controls, and is influenced by, the vegetation regime via geomorphic processes (Corenblit et al. 2024). This can include non-woody vegetation, but more commonly focuses on woody vegetation (i.e., Wohl et al. 2019). The distribution and movement of sediment and vegetation varies in time and space (Corenblit et al. 2007; Gurnell 2007; Kramer and Wohl 2017). Riverscape vegetation from grasses to trees changes the flow of energy (Czarnomski et al. 2012; Manners et al. 2014, 2015; Simon and Collison 2002), and the root strength of riparian vegetation alters the cohesiveness of floodplain sediments (Pollen and Simon 2005; Pollen-Bankhead and Simon 2010), affecting the spatial and temporal patterns of sediment transport and deposition at multiple scales (Gurnell, Corenblit, et al. 2016; Gurnell, Rinaldi, et al. 2016). In fact, the presence of vegetation can shift river channel character, maintaining variation in the depth of single-thread channels and supporting island dynamics in braided river systems (Tal and Paola 2007; Zanoni et al. 2008). In some riverscapes, woody vegetation is dominant and expected, in others vegetation is more sparse (e.g., semiarid and arid environments). Therefore, the vegetation regime can include wood inputs, where magnitude, frequency, rate, timing, duration, and mode of wood recruitment, transport, and storage in riverscapes are key (Box 1; Wohl et al. 2019). Wood, similar to water and sediment, interacts with and influences fluxes of water, sediment, organic matter, and solutes within riverscapes (Poff and Ward 1989; Stromberg et al. 1996; Walker et al. 1995; Wohl et al. 2019). However, the role of large pieces of mobile, woody material is far from the only route by which vegetation creates healthy riverscapes. This feedback is an interaction between biology and physical processes, increasing storage of organic matter and nutrients (Beckman and Wohl 2014; Bilby and Likens 1980; Castro and Thorne 2019; Raikow et al. 1995) and catalyzing nutrient uptake (Buckley and Triska 1978; Krause et al. 2014). The heterogeneous instream and floodplain habitats resulting from natural regimes promote greater niche partitioning and biodiversity in riverscapes (e.g., Torgersen et al. 2006).
In riverscapes that intersect forested areas or support their own riparian forests, vegetation regimes may include natural accumulations of wood recruited into the channel (Ruiz-Villanueva et al. 2016). This may occur as channels laterally adjust; trees may fall directly into or across the channel, or mass-wasting can occur from hillslopes (Benda et al. 2003; Bertoldi et al. 2013; Wohl 2013). As wood gets realigned and reorganized in channels, where wood is found may not be near the source (Abbe and Montgomery 1996, 2003; Piégay 2003), therefore understanding of wood sources and accumulation needs to occur at the catchment scale. A vegetation regime that includes wood often is characterized by punctuated delivery and uneven distribution (Wohl et al. 2019). Recruited trees can act as a direct obstruction to flow upon which other woody material in transport accumulates or can itself be mobilized and transported to accumulate elsewhere (refer to extensive reviews of wood recruitment, accumulation, and transport; Gurnell et al. 2002; Wohl 2013). Large wood jams create important pool habitat, provide cover and refugia from high flow events, and promote a diversity of local hydraulics important for fishes, invertebrates, and amphibians (e.g., Abbe and Montgomery 1996, 2003; Collins et al. 2012; Wohl et al. 2019).

<figure><img src="image_4.png" /></figure>

Representation of example timelines at which a type of vegetation regime (here, wood) could be accumulated and stored within a riverscape. During/following a mass event (dashed line), wood recruitment happens infrequently but residence of wood lasts longer. Slow accumulation (dotted line) reflects episodic events that accumulate wood until the wood slowly decays. Short residence recruitment (solid line) refers to continuous accumulation and transport of wood, such that the overall amount is roughly constant. Principles to assess riverscape health synthesize the range of variability across these timeframes in ways that are appropriate for the type of river under consideration (Brierley and Fryirs 2005). Figure concepts adapted from Wohl et al. (2019).

**4.3 | Riverscapes Need Structural Forcing to Support Diversity**

Riverscapes need structural elements, including inorganic elements and biologically derived elements, to force changes in flow patterns that produce physically diverse habitats, resulting in diverse residence times for water, sediment, and vegetation over various spatial and temporal scales.

Structural elements are discrete objects that directly influence hydraulics (Wheaton et al. 2015) and can include a wide range of organic (e.g., wood jams, beaver dams, macrophyte beds, bank, and floodplain vegetation) and inorganic material (e.g., bedrock, boulders) that cause obstructions to flow within the channel and across the valley bottom during flows of various magnitudes and frequencies. Structure forces a variety of flow depths and velocities (refer to Natural Resources Conservation Service (NRCS) 2007 for overview of stream hydraulics). Any structural element in a free-flowing stream causes flow paths to diverge and converge (e.g., around, over,

percolate through and under, back-up behind, and split). For many rivers, increased structural diversity induces beneficial feedback loops between geomorphic processes (e.g., erosion, deposition, sediment sorting, and the formation of geomorphic features), hydrologic processes (e.g., exchange of surface and groundwater vertically and laterally throughout the valley bottom), ecologic processes (e.g., growth of diverse types and age classes of riparian plants, beaver activity), and the resulting supply of structural elements that sustain these processes over space and time (Wohl et al. 2019). Laterally unconfined rivers such as wandering and meandering beds with gravel and sand substrates are expected to have a more complex and diverse structure if in good health (Figure 3a). However, not all healthy rivers have high diversity and high levels of structural elements present (Zhang and Fryirs 2024). For example, laterally unconfined rivers that have discontinuous channels or are formed in fine-grained materials are expected to be relatively geomorphically simple if in good health (Figure 3b). For these river types, increasing structural diversity through restoration can be deleterious to riverscape health (Fryirs 2015; Fryirs and Brierley 2009). The resulting variability of flow path direction and cohesiveness from any amount of structure
<figure><img src="image_5.png" /><figcaption>**FIGURE 3** | Expectations of diversity versus simplicity for different river types. Blue dashed line represents the valley bottom margin. Some river types are expected to have a diverse assemblage of geomorphic features when in good health. For example, (a) laterally unconfined wandering gravel bed rivers (Salmon River, Vancouver Island, Canada). However, other river types are expected to have a simple assemblage of geomorphic features when in good health. For example, (b) laterally unconfined rivers with discontinuous or absent channels (Mulwaree River, NSW, Australia). Source of left panel aerial images: Google Earth. Source of right panel photos: (a, b) K. Fryirs, Macquarie University.</figcaption></figure>

drives a variety of geomorphic processes (i.e., erosion, deposition, transport, sorting, and storage of sediment) at meso- and micro-scales that shape the ever-changing suite of geomorphic units (e.g., riffles, runs, pools) and habitats found in healthy riverscapes (Brierley and Fryirs 2005, 2022; Wohl 2017).

Structure forces more frequent, more consistent, and extensive connectivity between the active channel and the floodplain (Wohl et al. 2019). In rivers that have been modified, many of the structural elements have been removed. In these situations, loss of structural diversity produces a feedback effect that further reduces the residence time of elements that maintain riverscape health (Wohl et al. 2019). Diverse flow paths and greater interaction between the active channel and floodplain increase the variability in the time it takes for water, sediment, and nutrients to move through the system (Wohl et al. 2019). More diverse residence times of water (i.e., different timing and amounts) can recharge groundwater levels, attenuate potentially damaging floods, cycle nutrients, modulate

water temperature, and slowly release water throughout the year, elevating or extending baseflows, resulting in ecosystem benefits (Covino 2017; Pollock et al. 2003; Wegener et al. 2017; Wohl 2016).

## 5 | Context Matters

How each principle of riverscape health may manifest in a specific riverscape varies based on temporal and spatial considerations of climatic, physiographic, and geologic settings (i.e., catchment position, reach type, valley setting, water, sediment, and vegetation regimes).

Riverscapes occur across a diverse range of climatic, physiographic, and geologic settings, and each has its own set of disturbances and history (i.e., legacy effects; Allan 2004) that
<figure><img src="image_6.png" /><figcaption>(b) Laterally unconfined, discontinuous channel, chain of ponds, fine grained</figcaption></figure>

<figure><img src="image_7.png" /></figure>

**FIGURE 4** | Application of the three principles of riverscape health to different river types. Left panel aerial images are the same as those in Figure 3 and show reaches that are in good health, while the right panels are for reaches of the same river type that are in poor health. (a-left) Salmon River, Vancouver Island, Canada, (a-right) Coldwater River near Kingsvale, British Columbia, Canada. (b-left, right) Mulwaree River, NSW, Australia. These examples demonstrate the importance of context and understanding how different river types are expected to operate if healthy. What is expected in terms of the amount of space, water, sediment and vegetation regimes, and structural diversity is specific to the river style and its environmental setting. (a) A laterally unconfined, continuous channel, wandering, gravel bed river style. The riverscape in the left panel is in good health because it has space to move and adjust, flow engages with the floodplain, vegetation quality and distribution is diverse, and has sediment erosion and deposition processes that maintain a diverse geomorphic structure. The riverscape can “cope” with upstream sediment load. By contrast, the riverscape in the right panel is constrained by engineering structures and stop banks resulting in limited space to move and lack of flow engagement with the floodplain. Vegetation is largely absent, of poor quality or homogenized, particularly in the active channel, where a diverse array of islands would be expected if in good health. The reach is sediment capacity limited meaning the geomorphic structure is less diverse than expected. (b) A laterally unconfined, discontinuous channel, chain of ponds, fine-grained river style. The riverscape in the left panel is in good health because it has a relatively simple geomorphic structure, dominant fine-grained vertical accretion processes, flow engagement with the floodplain, and vegetation quality and distribution as expected for that river style. No evidence of coarse-grained sediment intrusion or head cuts exist that could threaten riverscape health. By contrast, the riverscape in the right panel has become constrained as incision of preferential flow paths have essentially disconnected flow from the floodplain. Head cuts are evident, and ponds are infilling with coarse sediments. Bars and ledges are present in the geomorphic structure of the riverscape, which is much more diverse than expected for this river style. Vegetation is dominated by pasture grass and has lost the aquatic associations expected for a healthy chain of ponds riverscape.

continue to influence and moderate the principles of river-
scape health long after the initial disturbance has ceased
(Allan 2004; Ward 1998; Wohl 2018; Wohl et al. 2024).
Different river types require different levels of space, regimes,
and structure to be considered in good health. Therefore, what
is expected in terms of space, water, sediment and vegetation
regimes, and diversity is specific to the type of river and its
environmental setting. For example, some riverscapes require
fine sediment whereas others do not. Some are expected to
have sparse vegetation associations (e.g., arid rivers) while

others have dense riparian zones if in good health. Some riv-
erscapes are naturally clogged with woody accumulations, or
dominated by beaver dam activity, whereas many others nat-
urally do not exhibit either. Some riverscapes are naturally
simple, while others are not (Fryirs and Brierley 2009; refer
to Figure 3). Figure 4 shows how the application of the three
riverscape principles can be contextualized to establish what
healthy (good condition) and unhealthy (poor condition) vari-
ants would look like, and by extension how they would func-
tion. Such appraisals set the context for identifying what is
currently lacking or limiting in a riverscape and considering
how this could be treated in restoration by working with the
river to self-heal (Fryirs et al. 2021; Kondolf 2011). Having this
context provides the evidence-base for “leaving a river alone”
if it is already in good health with the processes and func-
tion expected for that river type.

Some of the key drivers and limiting factors on riverscape
recovery potential are the amount of space available within
valley bottoms, the flow regime, and the type, availability,
and amount of vegetation and sediment. Even within specific
basins, the contributing upstream catchment varies consid-
erably in size from headwater streams to mainstem rivers,
which, together with precipitation patterns, gradient, and
confinement, determine stream power and the ways rivers use
energy. Similarly, ranges in elevation, climate, geology, and
soils determine the availability, recruitment, transport rate,
and residence time of structural elements (e.g., woody mate-
rial, colluvium; Collins et al. 2012; Kramer and Wohl 2017;
Nakamura et al. 2000; Poff et al. 1997; Wohl 2013), such
that mobile structural elements are rare in some riverscapes
(e.g., tall grass prairie; Dodds et al. 2004) and extremely
abundant in others (e.g., rainforest; Keller et al. 2004). For ex-
ample, rates of biological productivity vary from rich riverine
wetland and beaver meadow systems to oligotrophic, granitic
forested systems (e.g., Koenig et al. 2019; Savoy et al. 2019).
Together, these differences in available space, structure,
landscape, and biogeomorphic settings affect the relative
extent of vertical, lateral, and longitudinal connectivity, in-
fluencing the capacity for attenuation of water and sediment
and the extent and variety of flow paths and timing. Brierley
et al. (2013) provide considerations including explicit ques-
tions and steps to contextualize riverscapes. Understanding
the overall context and potential in different riverscape bio-
geomorphic settings is therefore critical in identifying key
processes, capacity, and expectations for restoration planning
(Beechie et al. 2010; Brierley and Fryirs 2005; Castro and
Thorne 2019; Gurnell, Corenblit, et al. 2016; Gurnell, Rinaldi,
et al. 2016; Wohl et al. 2005). Assessing how humans have
modified and controlled processes that can obscure natural
functioning is critical for maximizing riverscape potential
within contemporary circumstances (e.g., Nadeau et al. 2024;
Polvi et al. 2020).

6 | Riverscapes Cannot Be Separated From Anthropogenic and Biogeomorphic Influences

The riverscape health principles largely focus on the bioge-
morphic principles driving riverscape processes, but anthro-
pogenic catchment-scale processes also influence riverscapes.
Riverscape health is defined based on intrinsic, biogeomorphic
characteristics (i.e., natural) of a riverscape. In concept this is
simple, but in practice we do not always know what is intrinsic
or natural for a riverscape. Most riverscapes now are subjected
to anthropogenic influences that cannot be ignored. Figure 4
illustrates a contrast between idealized extremes in riverscape
health, but what is possible in the context of anthropogenic
influence can lie somewhere in between these extremes. That
is, the principles of riverscape health do not suggest that riv-
erscapes can only exist as fully healthy, or unhealthy. Instead,

the principles aid in defining a continuum of condition, where
moving from an unhealthy to healthy state can yield ecosystem
benefits.

Cumulative responses to contemporary impacts and legacy
effects must be considered within the context of riverscape
health. For example, point and nonpoint source pollution
within a catchment, including heavy metals, industrial or
urban waste, or agricultural runoff (including excessive fine
sediments), can negatively impact water quality (Pendergraph
et al. 2021; Singh and Gupta 2016), potentially offsetting or
preventing the ecosystem benefits of riverscape restoration.
Factors outside of the riverscape such as road networks (Jones
et al. 2000), logging (Hartman 2004; Kreutzweiser et al. 2008),
and livestock grazing (Belsky et al. 1999), in addition to those
inside the riverscape (dams and diversions; Baker et al. 2011;
Ligon et al. 1995; Liro 2019; Volke et al. 2015, 2019), can af-
fect natural sediment, hydrologic, and vegetation regimes and
resulting nutrient and biotic interactions. Disruption of nat-
ural disturbances such as fire regimes (Boisramé et al. 2019;
Gustine et al. 2022; Neary et al. 2003) and removal of eco-
system engineers (e.g., beaver *Castor* spp., Wohl 2021; salmon
*Oncorhynchus* spp., Janetski et al. 2009; Box 2) or predator-
prey regimes (e.g., gray wolves *Canis lupus* in the Greater
Yellowstone Ecosystem; Beschta and Ripple 2006, 2010) limit
the potential for habitat mosaics in riverscapes, reducing over-
all dynamism.

While we do not attempt to describe all of the ways by which
catchment uses by humans can limit riverscape health,
all riverscapes must be considered nested within a socio-
ecological landscape (Dunham et al. 2018; Hand et al. 2018;
Hawley 2018; Murphy et al. 2022; Peipoch et al. 2015).
Coherent understanding of these circumstances is required
to inform monitoring, conservation, and restoration programs
(Brierley and Fryirs 2016). Legacy effects (sensu “ghost[s] of
land use past”; Harding et al. 1998) of vegetation removal in
the catchment, removal of structure in the active channel,
mining, road construction, grazing, loss of ecosystem engi-
neers, water diversion, and so forth, even if not contemporar-
ily occurring, produce enduring biogeomorphological change
in riverscapes (Allan 2004). These legacies influence resulting
expectations and capacity (Fryirs 2024) and what trajectories
of recovery are even possible (Brierley and Fryirs 2016). Given
the legacy of human alterations, even societal expectations
of what a healthy riverscape is and what a healthy riverscape
can provide have changed over time (Thorel et al. 2018). Each
of the principles depicts elements of riverscapes that influ-
ence health relative to recovery potential, where potential is
the likelihood that riverscape health will improve relative to
current condition, given the limiting factors and pressures op-
erating in the system (Brierley and Fryirs 2016; Fryirs 2024).
The principles will likely be influenced by human activity in
almost all circumstances, and even legacy effects can affect
the potential for a riverscape or expectations for recovery (e.g.,
Kondolf et al. 2002). The degree to which riverscape health is
actualized ultimately will depend on the extent to which these
influences can be minimized. With an understanding of riv-
erscape principles, communities can make informed choices
about the balance of riverscape health and ecosystem benefits
derived (Wenger et al. 2025).
Though riverscapes provide habitat with undeniable importance to the life cycle of terrestrial and aquatic organisms, some organisms directly or indirectly regulate riverscape health. Often recognized as ecosystem engineers, these biological elements of a healthy riverscape are key components of the biogeomorphic feedback critical for structuring, creating, and maintaining healthy riverscapes (e.g., Polvi and Sarneel 2018). Here we provide examples where riverscapes are reliant on biological interactions, but we acknowledge that many more examples exist, and the relative importance of ecosystem engineers will depend on the riverscape context.

## Primary Producers

Algal mats and biofilms, macrophytes, and riparian vegetation alter sediment and hydrology, shaping riverscapes (A. Gurnell 2014; Polvi and Sarneel 2018). Benthic sediments colonized by biofilms and algal mats are more protected from erosion, and feedbacks exist between the shapes of the algal mats and flow, creating dynamic influences of these primary producers on riverscapes (Battin et al. 2003; Rusconi et al. 2010). Within patches of submerged and emergent macrophytes, flow velocity is attenuated, causing settling and storage of fine sediment (A. Gurnell 2014; Gurnell et al. 2006; Micheli and Kirchner 2002b, 2002a). Riparian vegetation adds support to stream bed and bank materials through root mats, increasing overall bed and bank cohesion, and reducing erosion (Han and Brierley 2020; Hawley and MacMannis 2019). The type and density of this vegetation can change the shape of the channel as a whole, determining the type and distribution of habitats it contains (Tal and Paola 2007; Zanoni et al. 2008).

## Macroinvertebrates

Benthic macroinvertebrates, including midges, caddisflies, and mussels, alter flow, sediment, and nutrient pathways (e.g., Chakraborty et al. 2022). Silk nets created by midges and caddisflies increase sediment stability and consolidate bed sediments, increasing overall benthic sediment storage (Albertson et al. 2014, 2019; Albertson and Allen 2015; Johnson et al. 2009; Statzner 2012). Cohesive beds of sedentary mussels also reduce flow velocities and consolidate sediment; however, burrowing mussels potentially increase erosion via bioturbation (Allen and Vaughn 2009).

## Beaver

Beaver dam activity provides important structural elements that alter hydraulics, with cascading effects to riverscapes (refer to Gurnell 1998; Naiman 1988; Pollock et al. 2003). Beaver activity includes construction and maintenance of dams, lodges, canals, tunnels, burrows, and the harvest of vegetation. Although beavers are found in larger rivers and lakes where they may build lodges or burrows, the equally affect smaller streams where they recruit wood to the channel, build dams, and excavate canals. Beavers undertake a variety of activities to modify, manipulate and maintain water levels to avoid predation (Müller-Schwarze 2017) and cultivate forage (Maestas et al. 2023). Beaver activity affects riparian function and diversity, aquatic food webs, geomorphology, hydrology, and biogeochemical cycling (Brazier et al. 2021; Maestas et al. 2023; Wohl 2021). In particular, the construction and maintenance of dams and beaver ponds that provide deep water habitats for beaver safety also lead to a diversity of flow paths and flow types (refer to Principle 3; free flowing, ponded, overland; Bartelt 2021), attenuating floods, protecting against incision, altering stream habitat and sediment loading, promoting riparian vegetation growth, increasing inundation during baseflows, and enhancing groundwater levels, exchange, and storage (Bouwes et al. 2016; Jordan and Fairfax 2022; Majerova et al. 2015; Westbrook et al. 2020).

## 7 | Benefits of Riverscape Health

When riverscapes have space, contain biogeomorphic-forcing elements, and have a diversity of water, vegetation, and sediment residence times, multiple benefits to aquatic and terrestrial species (including humans) result. Through a mosaic of habitats, intact riverscapes support high biodiversity (Cooke and Zack 2008; Kivinen et al. 2020; Naiman 1988; Tockner and Stanford 2002; Wright et al. 2002), important ecological processes (Hilty and Merenlender 2004; Rouquette et al. 2013; Tremblay and St. Clair 2011), and resulting regimes (e.g., thermal and nutrient; Pringle et al. 1988; Steel et al. 2017; Tonolla et al. 2010). Transport and processing of nutrients, sediment, and pollutants (Millenium Ecosystem Assessment 2005; Puttock et al. 2017, 2018; Shepherd and Nairn 2020; Short et al. 2015) that maintain water quality results from structural forcing, and longitudinal, lateral, and vertical connectivity of healthy riverscapes. Even economic markets can result from ecosystem benefits derived from riverscape

health (Brauman et al. 2007; Jarrad et al. 2018; Nicholls and Crompton 2017)—some examples include carbon and nutrient storage and sequestration, forage for livestock, increased house prices, and recreational opportunities. Riverscapes, which are included in “blue spaces” (aquatic environments; akin to “green spaces”), positively influence human mental and physical health directly and indirectly (White et al. 2020; Zuo et al. 2020), especially when the riverscape is healthy.

Healthy riverscapes promote important processes that enhance resilience to natural disturbances such as droughts, fires, and floods, even as these events are further exacerbated by a changing climate (e.g., mega-fires, Fairfax et al. 2024; Fairfax and Whittle 2020; Fryirs et al. 2022). We position riverscape resilience here similar to Brierley and Fryirs (2024): resilient riverscapes adjust, change, and evolve in response to disturbance with different structures and functions. The increase in and maintenance of riparian vegetation productivity over time, even through dry times, is possible
with healthy flow regimes (including floods; Bendix 1997), struc-
tural complexity, and increased water residence times (Fesenmyer
et al. 2018; Pilliod et al. 2021; Silverman et al. 2019). The slowing of
water also attenuates small to medium flood peaks and increases
flood peak travel times (Fryirs et al. 2023; Gregory et al. 1985),
and decreases erosional energy downstream (Wohl 2017).
Furthermore, inundation of soils, active channels, and vegetation
within valley bottoms can resist the expansion of fire by acting as
natural barriers (Fairfax et al. 2024; Fairfax and Whittle 2020).

8 | Using the Riverscape Health Principles

At the broadest scale, these riverscape health principles serve as the basis to establish a framework for policies, procedures, and regulations to promote, conserve, and restore healthy riparian, wetland, and riverine habitats. Essentially, these principles highlight that riverscape health and the ecosystem benefits that can be gained from healthy riverscapes are not just limited to the area accommodated by the active channel. Promoting riverscape health can enhance riverscape benefits—improving from current condition to a wider range and volume of reciprocal social values and benefits. Clearly articulated principles of riverscape health can help inform how and what is monitored to objectively assess the status and trends of riverscape conditions in relation to policy objectives (Flitcroft et al. 2022).

Coherent, catchment-scale analyses are required to operation-
alize these principles (e.g., Brierley and Fryirs 2005; Fausch

et al. 2002; Fryirs et al. 2021; Gurnell, Corenblit, et al. 2016; Gurnell, Rinaldi, et al. 2016). At a local scale, the principles can be applied to compare similar systems to aid in defining riverscape health for areas without baseline or historical contexts, help identify which aspects of riverscape health are missing. The principles can also help establish realistic goals and objectives for management, conservation, and restoration actions, and can guide informed discussions with landowners and managers about appropriateness of management actions and potential outcomes. Moreover, assessing and understanding how these riverscape health principles can be used is critical to set realistic expectations about how that riverscape should, or could, look and behave if in good health (Brierley and Fryirs 2005). Perhaps most importantly, practitioners, academics, and policymakers can apply these principles to prioritize and design riverscape restoration and management actions across a variety of spatial scales (Figure 5; specific case studies and applications can be accessed through the “River Styles Framework” website). This allows for defensible, efficient resource allocation to address limiting factors and restore ecosystem benefits, advancing the needs of multiple interested and affected parties.

Through time, researchers and practitioners will be able to ex-
pand examples of riverscape metrics that assess status and track
trends in the context of riverscape health principles. The three
principles provide a nexus that allows communities and individ-
uals to focus on shared values and create expectations for recov-
ery within the practical reality that riverscape health is shaped
by natural processes within contemporary constraints. The idea

<figure><img src="image_8.png" /><figcaption>**FIGURE 5** | Steps for applying riverscape principles in practice to recover riverscape health (based on the River Styles Framework: Brierley and Fryirs 2005; Fryirs 2015).</figcaption></figure>
that context matters (i.e., “it depends”) allows three relatively
simple principles to frame what healthy looks like for a specific
riverscape. With the three principles, the enormous range of
natural diversity can be comfortably expressed in its own spe-
cific context, while not losing sight of riverscape health.

Author Contributions

Hayley Corrine Glassic: writing – original draft (equal), writing – review and editing (equal). Robert Al-Chokhachy: writing – original draft (equal), writing – review and editing (equal). Joseph Wheaton: writing – original draft (equal), writing – review and editing (equal). William W. Macfarlane: writing – original draft (equal), writing – review and editing (equal). Chris E. Jordan: writing – original draft (equal), writing – review and editing (equal). Brian Murphy: writing – original draft (equal), writing – review and editing (equal). Scott Shahverdian: writing – original draft (equal), writing – review and editing (equal). Stephen Bennett: writing – original draft (equal), writing – review and editing (equal). Nicolaas Bouwes: writing – original draft (equal), writing – review and editing (equal). Kirstie Fryirs: writing – original draft (equal), writing – review and editing (equal). Gary Brierley: writing – original draft (equal), writing – review and editing (equal). Damion Ciotti: writing – original draft (equal), writing – review and editing (equal). Philip Bailey: writing – review and editing (equal). Karen Bartelt: writing – review and editing (equal). Barbara Belletti: writing – review and editing (equal). Simone Bizzi: writing – review and editing (equal). James Brasington: writing – review and editing (equal). Reid Camp: writing – review and editing (equal). Emily Fairfax: writing – review and editing (equal). Jordan Gilbert: writing – review and editing (equal). Justin Jimenez: writing – review and editing (equal). Jeremy Maestas: writing – original draft (equal), writing – review and editing (equal). Timmie Mandish: writing – review and editing (equal). Amy McNamara: writing – review and editing (equal). Scott Miller: writing – review and editing (equal). Baptiste Morizot: writing – review and editing (equal). Mathias Perle: writing – review and editing (equal). Hervé Piégay: writing – review and editing (equal). Helen Reid: writing – review and editing (equal). Lindsay V. Reynolds: writing – review and editing (equal). W. Carl Saunders: writing – review and editing (equal). Alden Shallcross: writing – review and editing (equal). Peter Skidmore: writing – original draft (equal), writing – review and editing (equal). Rose Smith: writing – review and editing (equal). Benoit Terrier: writing – review and editing (equal). Gus Wathen: writing – review and editing (equal). Nick Weber: writing – review and editing (equal).

Acknowledgments

Any use of trade, firm, or product names is for descriptive purposes only
and does not imply endorsement by the U.S. Government. We thank
two anonymous reviewers as well as a selected USGS reviewer for their
comments to improve this work.

Conflicts of Interest

The authors Nicolaas Bouwes (N.B.), Stephen Bennett (S.B.), and Joseph Wheaton (J.W.) declare a potential, perceived conflicts of interest as they are co-owners of a private, design-build restoration firm, Anabranch Solutions LLC. As owners, N.B., S.B., and J.W. receive payments for performing the assessment of riverscape health, prioritizing restoration actions, designing restoration and management interventions, as well as construction of riverscape restoration efforts. Refer to https://www.anabranchsolutions.com/mitigating-potential-coi.html for how they mitigate potential conflict of interests from becoming realized.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created
or analyzed in this study.

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