INCORPORATING UNCERTAINTY IN THE DESIGN OF STREAM CHMNEL MODIFICATIONS¹

Abstract

The designs of stream channel naturalization, rehabilitation, and restoration projects are inherently fraught with uncertainty. Although a systematic approach to design can be described, the likelihood of success or failure of the design is unknown due to uncertainties within the design and implementation process. In this paper, a method for incorporating uncertainty in decision‐making during the design phase is presented that uses a decision analysis method known as Failure Modes and Effects Analysis (FMEA). The approach is applied to a channel rehabilitation project in north‐central Pennsylvania. FMEA considers risk in terms of the likelihood of a component failure, the consequences of failure, and the level of difficulty required to detect failure. Ratings developed as part of the FMEA can provide justification for decision making in determining design components that require particular attention to prevent failure of the project and the appropriate compensating actions to be taken.

Integrating ecology with hydromorphology: a priority for river science and management

“…Recent developments using Bayesian statistics, information-gap theory and other methods illustrate how this may be possible in eco-hydromorphology (Regan et al, 2005;Halpern et al, 2006). At a higher level, frameworks for placing management within the context of all uncertainties } known and unknown } are being developed (Johnson and Brown, 2001). …”

The Scope of Uncertainties in River Restoration

“…Wissmar and Bisson (2003b) asserted that 'a better understanding of variability and uncertainty is critical to the successful implementation of restoration programs for aquatic and riparian systems.' Yet, buried within a rich literature on restoration are only occasional passing mentions of uncertainty (Brookes and Shields, 1996) and a handful of explicit treatments (Johnson and Brown, 2001;Johnson et al, 2002;Johnson and Rinaldi, 1997;Johnson and Rinaldi, 1998;Wissmar and Bisson, 2003c). These studies understandably tend to focus on a specifi c type of uncertainty that might be reasonably articulated within a specifi ed page limit, so a more holistic treatment of uncertainty is necessary (Newson and Clark, see Chapter 14;Van Asselt, 2000).…”

“…Several authors have departed from this view towards a more progressive view of embracing uncertainty (Johnson and Brown, 2001;Newson and Clark, see Chapter 14). One of the earlier proponents of this view appears to be Holling (1978), who argued:…”

“…Especially in long term policy analysis (the next 20-100 years) decision makers are faced with what Lempert et al (2003) referred to as 'deep uncertainty'. Johnson and Brown (2001) argued that incorporating uncertainty into restoration design allows practitioners to consider multiple causes and hypothesised fi xes; thereby reducing the potential for project failure. It has been argued here that uncertainty is not necessarily bad, but ignorance of it can foster unrealistic expectations.…”

The Sustainability of Restored Rivers: Catchment‐Scale Perspectives on Long Term Response

“…It has been suggested that uncertainty can now be incorporated into the design of stream channel modifi cations (Johnson and Brown, 2001) for stream restoration, rehabilitation and stabilization, but spatial and temporal implications still need to be incorporated fully. There is a continuum of spatial scales in river system behaviour, each having a temporal dimension so that, in order to fi t river channel restoration into an appropriate time and space perspective, the drivers which arise from space and time dimensions must be considered.…”