Restoring Ecological Integrity in Highly Regulated Rivers: The Role of Baseline Data and Analytical References

Abstract

The goal of restoring ecological integrity in rivers is frequently accompanied by an assumption that a comparative reference reach can be identified to represent minimally impaired conditions. However, in many regulated rivers, no credible historical, morphological or process-based reference reach exists. Resilient restoration designs should instead be framed around naturalization, using multiple analytical references derived from empirically-calibrated field- and model-based techniques to develop an integrated ecological reference condition. This requires baseline data which are rarely collected despite increasing evidence for systematic deficiencies in restoration practice. We illustrate the utility of baseline data collection in restoration planning for the highly fragmented and regulated lower Merced River, California, USA. The restoration design was developed using various baseline data surveys, monitoring, and modeling within an adaptive management framework. Baseline data assisted in transforming conceptual models of ecosystem function into specific restoration challenges, defining analytical references of the expected relationships among ecological parameters required for restoration, and specifying performance criteria for post-project monitoring and evaluation. In this way the study is an example of process-based morphological restoration designed to prompt recovery of ecosystem processes and resilience. For the Merced River, we illustrate that project-specific baseline data collection is a necessary precursor in developing performance-based restoration designs and addressing scale-related uncertainties, such as whether periodic gravel augmentation will sustain bed recovery and whether piecemeal efforts will improve ecological integrity. Given the numerous impediments to full, historical, restoration in many river systems, it seems apparent that projects of naturalization are a critical step in reducing the deleterious impacts of fragmented rivers worldwide.

Riparian vegetation research in Mediterranean-climate regions: common patterns, ecological processes, and considerations for management

“…The increased understanding achieved over the last decade in riparian vegetation pattern and functioning provides a solid basis for rational resource management in med-river ecosystems (e.g., Downs et al, 2011). Approaches with strong precedent include releasing environmental flows to benefit riverine and riparian species (Hughes & Rood, 2003;Rood et al, 2005), as well as non-native species management .…”

Status and trends of dam removal research in the United States

“…The necessity of a control, however, depends on the type of question being addressed. Impact studies (those without a control) can provide important insights into rates of physical and ecological changes after dam removal . However, these studies do not permit the interpretation of post‐removal changes in the context of pre‐removal or control site conditions (e.g., upstream conditions).…”

“…Impact studies (those without a control) can provide important insights into rates of physical and ecological changes after dam removal. 39 However, these studies do not permit the interpretation of post-removal changes in the context of pre-removal or control site conditions (e.g., upstream conditions). Whether a study employs a temporal and/or spatial control depends on funding availability, sufficient advance notice of dam removal, the existence of an appropriate control site (e.g., McHenry and Pess 40 ), and the types of research questions being addressed.…”

The anthropogenic nature of present-day low energy rivers in western France and implications for current restoration projects

“…This is crucial for the rivers studied because their low energy implies long-term morphological adjustments for which the controlling factors are difficult to identify in contrast with high energy streams which can rapidly adjust their morphology to changes in governing conditions, making them easier to track (e.g., Liébault and Piégay, 2002;Comiti, 2012). We aim to demonstrate the relevance of a holistic approach to these specific fluvial systems that includes the collection of baseline data (Downs et al, 2011) and understanding of the trajectories over the long-term to develop objectives for sustainable management (Brown, 1997(Brown, , 2002Downs and Gregory, 2004;Brierley and Fryirs, 2005;Froyd and Willis, 2008;Hughes et al, 2008;Higgs et al, 2014;Kondolf and Podolak, 2014). The extent to which present understanding of the low energy systems is, and could be, used is discussed and the requirements for future research identified.…”