110
connectivity, as well as lateral and vertical connectivity, by creating more natural
flow regimes.
An important consideration is that restoration is undertaken in a human or societal context in which perceptions of desired river characteristics and river health are
of critical importance. Reach-scale restoration, in particular, is more likely to be
driven, or at least strongly influenced, by stakeholders in local communities,
whereas watershed-scale restoration is more commonly driven by government
resource-management agencies. Reach-scale restoration may involve esthetic or
recreational enhancements that do not necessarily improve ecological functions in a
river corridor (Bernhardt et al. 2007). Reach-scale restoration sometimes also seeks
to create conditions that are not natural or ecologically appropriate for a particular
river corridor (Brierley and Fryirs 2009; Fryirs and Brierley 2009), as in the many
examples of braided rivers that are viewed as esthetically unattractive and reconfigured to a meandering planform (Kondolf et al. 2001). These scenarios can occur
where there is a gap between scientific understanding of a river ecosystem and societal perceptions.
Large wood in river corridors illustrates this gap very well. An extensive literature documents the numerous beneficial physical and ecological effects of wood in
rivers (Gregory et al. 2003; Wohl 2017) and wood was abundant historically in
forested river corridors in all regions of the world (Gregory et al. 2003; Wohl
2014). Nonetheless, much of contemporary river management and restoration continues to remove wood from channels and floodplains either because of perceived
safety hazards or simply for esthetic reasons (Wohl 2015). Surveys conducted
among university students in introductory geology or physical geography classes
in the United States and Europe indicate that most students have highly negative
perceptions of wood in river corridors (Chin et al. 2008), whereas similar surveys
indicate generally positive perceptions of wood among experienced river managers
(Chin et al. 2014).
After decades of river restoration projects, how successful have these efforts
been? Numerous evaluations of river restoration by river scientists emphasize three
points (Wohl et al. 2015b). First, most restoration projects, especially reconfiguration projects on small to medium-sized rivers, do not include monitoring to quantitatively and objectively evaluate whether restoration goals were achieved (e.g.,
Bernhardt et al. 2005). Souchon et al. (2008), for example, note that there has been
little validation monitoring of the response of aquatic species to restored flow
regimes. Second, a substantial proportion of restoration projects do not achieve significant improvements in river function as reflected in water quality, ecological
communities, or ecosystem services (Lepori et al. 2005; Bernhardt and Palmer
2011; Violin et al. 2011; Palmer and Hondula 2014). Third, river scientists and managers must work to more effectively involve the non-scientific community in planning and implementation of river restoration (Eden et al. 2000; Pfadenhauer 2001;
Wade et al. 2002; Eden and Tunstall 2006; Eden and Bear 2011). There are numerous explanations for why many restoration projects do not achieve significant
improvements. These include restoration activities that are not appropriate for
4 Toward Sustainable Rivers and Water Resources
connectivity, as well as lateral and vertical connectivity, by creating more natural
flow regimes.
An important consideration is that restoration is undertaken in a human or societal context in which perceptions of desired river characteristics and river health are
of critical importance. Reach-scale restoration, in particular, is more likely to be
driven, or at least strongly influenced, by stakeholders in local communities,
whereas watershed-scale restoration is more commonly driven by government
resource-management agencies. Reach-scale restoration may involve esthetic or
recreational enhancements that do not necessarily improve ecological functions in a
river corridor (Bernhardt et al. 2007). Reach-scale restoration sometimes also seeks
to create conditions that are not natural or ecologically appropriate for a particular
river corridor (Brierley and Fryirs 2009; Fryirs and Brierley 2009), as in the many
examples of braided rivers that are viewed as esthetically unattractive and reconfigured to a meandering planform (Kondolf et al. 2001). These scenarios can occur
where there is a gap between scientific understanding of a river ecosystem and societal perceptions.
Large wood in river corridors illustrates this gap very well. An extensive literature documents the numerous beneficial physical and ecological effects of wood in
rivers (Gregory et al. 2003; Wohl 2017) and wood was abundant historically in
forested river corridors in all regions of the world (Gregory et al. 2003; Wohl
2014). Nonetheless, much of contemporary river management and restoration continues to remove wood from channels and floodplains either because of perceived
safety hazards or simply for esthetic reasons (Wohl 2015). Surveys conducted
among university students in introductory geology or physical geography classes
in the United States and Europe indicate that most students have highly negative
perceptions of wood in river corridors (Chin et al. 2008), whereas similar surveys
indicate generally positive perceptions of wood among experienced river managers
(Chin et al. 2014).
After decades of river restoration projects, how successful have these efforts
been? Numerous evaluations of river restoration by river scientists emphasize three
points (Wohl et al. 2015b). First, most restoration projects, especially reconfiguration projects on small to medium-sized rivers, do not include monitoring to quantitatively and objectively evaluate whether restoration goals were achieved (e.g.,
Bernhardt et al. 2005). Souchon et al. (2008), for example, note that there has been
little validation monitoring of the response of aquatic species to restored flow
regimes. Second, a substantial proportion of restoration projects do not achieve significant improvements in river function as reflected in water quality, ecological
communities, or ecosystem services (Lepori et al. 2005; Bernhardt and Palmer
2011; Violin et al. 2011; Palmer and Hondula 2014). Third, river scientists and managers must work to more effectively involve the non-scientific community in planning and implementation of river restoration (Eden et al. 2000; Pfadenhauer 2001;
Wade et al. 2002; Eden and Tunstall 2006; Eden and Bear 2011). There are numerous explanations for why many restoration projects do not achieve significant
improvements. These include restoration activities that are not appropriate for
4 Toward Sustainable Rivers and Water Resources