By Ken Gregory, University of Southampton UK and Anne Chin, University of Colorado, Denver
Rivers and streams are important to the 54% of the world’s population living in urban areas. Although environmental pollution, and its reduction, were a first concern for streams in urban areas, river channel quality has recently attracted more attention. For example, restoration schemes have been undertaken for specific areas, and ‘daylighting’ is now uncovering portions of buried rivers (The Guardian, 2017). Research has engaged several disciplines, with the urban stream syndrome evident in the work of ecologists, and geomorphologists showing effects of changed processes in urban rivers, with research results useful for management (e.g. Chin and Gregory, 2009). Hitherto emphasis has been on parts of urban areas or on specific stream problems, but it is now feasible to use a more holistic approach to evaluate the effects of changes and management on the stream system in a single area.
In our recent paper, ‘Evaluation of the imprint of urban channel adjustment and management’, we report analysis of the area of Fountain Hills, Arizona, a town area of 52.4 km2. In this area, which has been urbanised since 1970, at least 43 individual wash channels from the McDowell Mountains flowed naturally eastward to the Verde River, and three drained westward. Population increased rapidly from 2,772 in 1980 to 22,489 in 2010, with the eventual prospect of >36,540 in 2050. Although stream channels were identified as the primary mechanism to remove storm waters, roads in Fountain Hills were built to function as storm drainage as an alternative to investing in costly, but infrequently needed, storm sewers. We have studied specific areas within Fountain Hills identifying channel effects of urbanisation (Chin and Gregory, 2001), the hazards (Gregory and Chin, 2002), and management implications (Chin and Gregory 2005). Analysis of the entire urban wash channel system enables us to evaluate how successful management of the washes has been.
Although evaluation is often employed as a component of environmental assessment, usually associated with specific projects in post-project appraisal, few geomorphic evaluations of adjusting channel systems have been conducted together with consideration of management success. We suggest that geomorphological success can be evaluated by considering three inter-related aspects of a managed urban drainage system: the functionality (does it work?), the appearance (does it look appropriate?), together with its resilience (is it sustainable?). For Fountain Hills, functionality is satisfactory in the 60% of wash length that has achieved naturalization; appearance is appropriate for that same wash length, although golf course developments produce wash lines at variance with the natural character. Short term resilience is accommodated by the wash management programme and by ongoing adaptive management. Land ownership, especially of private land with areas developed for golf courses, accounts for some of the variations encountered because such areas are not subject to the controls upon public land.
Overall, therefore, management of the wash system in Fountain Hills has been successful, enabled by adaptive management including a wash management programme and new policies implemented for the most recently developed areas. However, the policy intention to maintain what is ‘natural’ has not been realised; it could have more realistically been stated as the need to undertake naturalization. This relates to the debate in the literature of several disciplines concerning what is ‘natural’ and the perception of ‘naturalness’, and in the EU Water Framework Directive, this is the ‘reference condition’ of high ecological status against which river condition is judged.
This evaluation approach, which could be applied to other areas, suggests that a holistic basin plan could be developed to anticipate geomorphological change throughout the basins outlining the most appropriate measures to adopt, thus reducing the need for adaptive management as urbanisation progresses. Whereas adaptive management is reactive to changes which have already occurred, and anticipatory management has been suggested for instream habitat (Beagle et al. 2016), should proactive catchment management be envisaged for adapting to future change? Such a proactive approach is analogous to catchment-scale longer-term perspectives in restoration (Gregory and Downs 2008), which enable geomorphic consequences to be included and managed.
Where washes have been modified, could geomorphologically-based alternatives be devised, and should design practices become more evident in both applied research and in contemporary learning and teaching? (Gregory 2017)
About the authors: Ken Gregory is Visiting Professor University of Southampton and Emeritus Professor University of London and was President of the BSG (2009-2014), Anne Chin is Professor Department of Geography and Environmental Sciences, University of Colorado, Denver and is currently Editor of Anthropocene.
Beagle , J. R., Kondolf, G. M., Adams, R. M. and Marcus, L. (2016). Anticipatory management for instream habitat: Application to Carneros Creek, California. River Research & Applications 32, 280-294.
Chin, A. and Gregory, K. J. (2001). Urbanization and adjustment of ephemeral stream channels. Annals Association of American Geographers 91, 595–608.
Chin, A. and Gregory, K. J. (2005). Managing urban river channel adjustments Geomorphology 69, 28-45.
Chin, A. and Gregory, K. J. (2009). From research to application: Management implications from studies of urban river channel adjustment. Geography Compass 3, 297–328.
Gregory, K. J. (2017). Putting physical environments in their place: The next chapter? The Canadian Geographer 61, 11–18.
Gregory, K. J. and Chin, A. (2002). Urban stream channel hazards. Area 34, 312–321.
Gregory, K. J. and Chin, A. (2017). Evaluation of the imprint of urban channel adjustment and management. The Geographical Journal doi:10.1111/geoj.12231
Gregory, K. J. and Downs, P. W. (2008). The sustainability of restored rivers: Catchment scale perspectives on long term response In Darby, S. and Sear, D. eds. River Restoration: Managing the uncertainty in restoring physical habitat. Wiley Chichester 253 – 286.
The Guardian (2017). A river runs through it: the global movement to ‘daylight’ urban waterways. The Guardian 8 September 2017.