124
emphasize diversity of form and process through space and time (McDonald et al.
2004; Brierley and Fryirs 2005), including the ability to adjust form and process in
response to changes in water and sediment inputs (Wohl 2012). Assessing the ability of a river corridor to geomorphically adjust to changing inputs is closer to assessing river functionality as proposed by Palmer and Febria (2012).
Regardless of the metrics used to assess river health, over-simplifying or standardizing the criteria for judging a river to be healthy must be avoided (Brierley and
Fryirs 2009). Some rivers are naturally depauperate in species because of harsh
physical or chemical conditions or a history of geographic isolation. Some rivers
naturally receive frequent large inputs of sediment because of tectonic uplift, a
semiarid climate, or erodible bedrock lithology. In these river corridors, the abundant sediment supply causes continual channel instability that can limit biodiversity.
Some rivers episodically change their form and function in response to naturally
occurring large floods. Other rivers may be fed predominantly by ground water
springs that create a very stable and consistent flow regime. In both cases, biodiversity may be lower than in river corridors with an intermediate level of disturbance
(Townsend et al. 1997). The key point is to recognize the levels of complexity, connectivity, and change naturally inherent in a particular river context.
4.6 Changing Perceptions of River Health and Naturalness
Not everyone views river corridors in the same way. As noted in the introductory
chapter, river scientists from different disciplines typically have disparate emphases
in conceptualizing rivers, although good progress has been made within the scholarly community in transcending disciplinary boundaries. River scientists, resource
managers, and indigenous communities, as well as stakeholders who use the river
for recreation versus those who rely on the river for water supply, may all have very
different perceptions of the river corridor and ideas about how it should be managed
(Eden et al. 2000). Many people, however, are moving beyond what might be termed
mainstream attitudes toward river corridors that have developed over the past two to
three centuries in high-income countries. These mainstream attitudes emphasize
physical simplicity, uniformity, and human control of river corridors in the context
of maximizing water supplies for consumptive uses and minimizing natural hazards
associated with rivers.
Some of this shift in attitude is driven by the recognition that ecosystem services
provided by rivers, which are critical to sustaining human societies, are declining
sharply in most river basins around the world. Some of the shift in attitudes toward
rivers is driven by a return within high-income societies to a recognition of the
inherent right of non-human organisms and ecosystems to exist. New Zealand, for
example, recognizes a river as a person in a legal context (Roy 2017). Some of the
shift is driven by the realization that completely natural river corridors have largely
ceased to exist, which can result in a longing for a more natural environment.
Whatever the combination of forces driving a shift in management of river corridors,
4 Toward Sustainable Rivers and Water Resources
emphasize diversity of form and process through space and time (McDonald et al.
2004; Brierley and Fryirs 2005), including the ability to adjust form and process in
response to changes in water and sediment inputs (Wohl 2012). Assessing the ability of a river corridor to geomorphically adjust to changing inputs is closer to assessing river functionality as proposed by Palmer and Febria (2012).
Regardless of the metrics used to assess river health, over-simplifying or standardizing the criteria for judging a river to be healthy must be avoided (Brierley and
Fryirs 2009). Some rivers are naturally depauperate in species because of harsh
physical or chemical conditions or a history of geographic isolation. Some rivers
naturally receive frequent large inputs of sediment because of tectonic uplift, a
semiarid climate, or erodible bedrock lithology. In these river corridors, the abundant sediment supply causes continual channel instability that can limit biodiversity.
Some rivers episodically change their form and function in response to naturally
occurring large floods. Other rivers may be fed predominantly by ground water
springs that create a very stable and consistent flow regime. In both cases, biodiversity may be lower than in river corridors with an intermediate level of disturbance
(Townsend et al. 1997). The key point is to recognize the levels of complexity, connectivity, and change naturally inherent in a particular river context.
4.6 Changing Perceptions of River Health and Naturalness
Not everyone views river corridors in the same way. As noted in the introductory
chapter, river scientists from different disciplines typically have disparate emphases
in conceptualizing rivers, although good progress has been made within the scholarly community in transcending disciplinary boundaries. River scientists, resource
managers, and indigenous communities, as well as stakeholders who use the river
for recreation versus those who rely on the river for water supply, may all have very
different perceptions of the river corridor and ideas about how it should be managed
(Eden et al. 2000). Many people, however, are moving beyond what might be termed
mainstream attitudes toward river corridors that have developed over the past two to
three centuries in high-income countries. These mainstream attitudes emphasize
physical simplicity, uniformity, and human control of river corridors in the context
of maximizing water supplies for consumptive uses and minimizing natural hazards
associated with rivers.
Some of this shift in attitude is driven by the recognition that ecosystem services
provided by rivers, which are critical to sustaining human societies, are declining
sharply in most river basins around the world. Some of the shift in attitudes toward
rivers is driven by a return within high-income societies to a recognition of the
inherent right of non-human organisms and ecosystems to exist. New Zealand, for
example, recognizes a river as a person in a legal context (Roy 2017). Some of the
shift is driven by the realization that completely natural river corridors have largely
ceased to exist, which can result in a longing for a more natural environment.
Whatever the combination of forces driving a shift in management of river corridors,
4 Toward Sustainable Rivers and Water Resources