Peter Cottingham

The urban stream syndrome: current knowledge and the search for a cure

Abstract The term “urban stream syndrome” describes the consistently observed ecological degradation of streams draining urban land. This paper reviews recent literature to describe symptoms of the syndrome, explores mechanisms driving the syndrome, and identifies appropriate goals and methods for ecological restoration of urban streams. Symptoms of the urban stream syndrome include a flashier hydrograph, elevated concentrations of nutrients and contaminants, altered channel morphology, and reduced biotic richness, with increased dominance of tolerant species. More research is needed before generalizations can be made about urban effects on stream ecosystem processes, but reduced nutrient uptake has been consistently reported. The mechanisms driving the syndrome are complex and interactive, but most impacts can be ascribed to a few major large-scale sources, primarily urban stormwater runoff delivered to streams by hydraulically efficient drainage systems. Other stressors, such as combined or sanitary sewer overflows, wastewater treatment plant effluents, and legacy pollutants (long-lived pollutants from earlier land uses) can obscure the effects of stormwater runoff. Most research on urban impacts to streams has concentrated on correlations between instream ecological metrics and total catchment imperviousness. Recent research shows that some of the variance in such relationships can be explained by the distance between the stream reach and urban land, or by the hydraulic efficiency of stormwater drainage. The mechanisms behind such patterns require experimentation at the catchment scale to identify the best management approaches to conservation and restoration of streams in urban catchments. Remediation of stormwater impacts is most likely to be achieved through widespread application of innovative approaches to drainage design. Because humans dominate urban ecosystems, research on urban stream ecology will require a broadening of stream ecological research to integrate with social, behavioral, and economic research.

Scientific Panels and Their Use in Environmental Flow Assessment in Australia

Abstract ‘Scientific’ or ‘Expert’ Panels have played an important role in water resource management in Australia in recent years. Scientific Panels have been an excellent knowledge exchange mechanism, providing a synthesis of multidisciplinary information and expertise on various river management issues, such as approaches to river rehabilitation, the setting of river health objectives or in developing environmental flow recommendations for regulated rivers. Many Panels have been convened to provide recommendations on environmental flows for regulated river systems within a relatively short time frame (eg rapid appraisals over 6–12 months) because of demanding Federal and State initiatives. As rapid appraisals utilise best-available information, they can be limited by the quality of existing information and the experience of Panel members. Indeed, many Scientific Panels are consistently confronted with the same range of information or knowledge gaps, particularly on the relationship between flow regime and the distribution and abundance of biota. The usefulness of Scientific Panels, as applied to river management issues such as environmental flow assessment, may decline unless there is investment to overcome key knowledge gaps such as the preferred flow regime of important riverine species or communities. The ongoing use of Scientific Panels for determining environmental flows would also be bolstered by the development of a clear process for selecting Panel members, protocols to guide the conduct of Panels, and the training of scientists to perform rapid appraisals of environmental flow requirements.

A Demonstration of the Flow Events Method: Environmental Flow Requirements of the Broken River

Abstract The Flow Events Method is a procedure for (i) assessing the ecological impact of flow regulation, (ii) developing environmental flow rules and (iii) optimising the operation of a water resource scheme to maximise environmental performance. The method is a systematic, transparent and defensible tool for use in environmental flows studies that makes use of available knowledge and facilitates the inclusion of expert opinion where necessary. It is not presented as a new technique, rather it is a logical and transparent procedure for integrating the concepts and data commonly used in environmental flow studies in Australia. The primary component of the method is the assessment of flow regulation based on changes in flow events that are considered to be important for specific ecological processes. This paper describes the application of the Flow Events Method to assess the impact of flow regulation in the Broken River catchment, including data and modelling requirements for this study. Six aspects of the flow regime are considered: (i) rapid increases in flows, (ii) rapid reduction in flows, (iii) the availability of slow water habitats, (iv) drying of the streambed, (v) the availability of shallow water habitats and (vi) inundation of channel benches.