Showing papers by "Tim D. Fletcher published in 2016"

Principles for urban stormwater management to protect stream ecosystems

Abstract: Urban stormwater runoff is a critical source of degradation to stream ecosystems globally. Despite broad appreciation by stream ecologists of negative effects of stormwater runoff, stormwater management objectives still typically center on flood and pollution mitigation without an explicit focus on altered hydrology. Resulting management approaches are unlikely to protect the ecological structure and function of streams adequately. We present critical elements of stormwater management necessary for protecting stream ecosystems through 5 principles intended to be broadly applicable to all urban landscapes that drain to a receiving stream: 1) the ecosystems to be protected and a target ecological state should be explicitly identified; 2) the postdevelopment balance of evapotranspiration, stream flow, and infiltration should mimic the predevelopment balance, which typically requires keeping significant runoff volume from reaching the stream; 3) stormwater control measures (SCMs) should deliver flow r...

Will it rise or will it fall? Managing the complex effects of urbanization on base flow

Abstract: Sustaining natural levels of base flow is critical to maintaining ecological function as stream catchments are urbanized. Stream base flow responds variably to urbanization. Base flow or water tables rise in some locations, fall in others, or remain constant. This variable response is the result of the array of natural (e.g., physiographic setting and climate) and anthropogenic (e.g., urban development and infrastructure) factors that influence hydrology. Perhaps because of this complexity, few simple tools exist to assist managers to predict baseflow change in their local urban area. We address this management need by presenting a decision-support tool that can be used to predict the likelihood and direction of baseflow change based on the natural vulnerability of the landscape and aspects of urban development. When the tool indicates a likely increase or decrease, managers can use it for guidance toward strategies that can reduce or increase groundwater recharge, respectively. An equivocal resul...

Urban hydrogeomorphology and the urban stream syndrome Treating the symptoms and causes of geomorphic change

Abstract: The urban stream syndrome is an almost universal physical and ecological response of streams to catchment urbanization. Altered channel geomorphology is a primary symptom that includes channel deepening, widening and instability. While the common approach is to treat the symptoms (e.g. modifying and stabilizing the channel), many stream restoration objectives will not be achieved unless the more vexing problem, treating the cause, is addressed in some way. Research demonstrates that the dominant cause of geomorphic change in streams in urban catchments is an altered flow regime and increase in the volume of stormwater runoff. Thus, managers can choose to treat the symptoms by modifying and controlling the channel to accommodate the altered flow regime, or treat the cause by modifying the flow regime to reduce the impact on channel morphology. In both cases treatments must, at the least, explicitly consider hydrogeomorphology—the science of the linkages between various hydrologic and geomorphic processes—t...

More than money: how multiple factors influence householder participation in at-source stormwater management

Abstract: Urban stormwater run-off is a threat to stream ecosystems. New approaches to stormwater management aim to protect urban streams from such impacts, by retaining, treating and using stormwater at its source. As up to ∼50% of runoff from urban surfaces comes from private property, fostering stormwater retention requires effective householder engagement. We evaluated householder participation in the Little Stringybark Creek project, a stormwater retrofit programme aimed at waterway protection, using qualitative enquiry through formal and informal interviews to identify factors that influenced participation. Participation was governed by multiple factors, with financial incentives and personal co-benefits of tanks primary motivators, while process complexity and distrust were primary barriers. Results suggest an approach combining education to encourage review of subjective norms and attitudes, with incentives to mitigate behavioural controls can transform public behaviour towards sustainable stormwater management.

Variability in stream ecosystem response to urbanization: Unraveling the influences of physiography and urban land and water management

Abstract: The geomorphic and ecological degradation of streams resulting from urbanization is well recognized. Recent reviews have hypothesized variability in ecological response to urbanization among stream types and among regions with varying climate and catchment soil and geology. Testing such hypotheses will be aided by the use of consistent metrics of the primary processes that drive urban-induced degradation of streams. We thus developed an urban typology distinguishing the common classes of urban land and water management that are hypothesized to have different effects on stream ecosystems. In developing the typology, we identify and emphasize the importance of step changes (thresholds) in the hydrologic consequences of urbanization, the often-unrecognized massive increase in drainage density of urban catchments, the difficulty in setting reference condition for many cities and the resulting difficulties in comparing responses to urbanization among cities. We critically assess the evidence for variability in...

The contribution of pharmaceutically active compounds from healthcare facilities to a receiving sewage treatment plant in canada

Abstract: Concentrations and percent loadings of pharmaceutically active compounds (PhACs) and other emerging contaminants released from healthcare facilities (2 hospitals and a long-term care facility) to a sewage treatment plant (STP) in a large urban sewershed were evaluated. An additional hospital outside the sewershed was also monitored. Fourteen of the 24 steroids/hormones and 88 of the 117 PhACs and emerging contaminants were detected at least once. Commonly used substances, including cotinine, caffeine and its metabolite 1,7-dimethylxanthine, ibuprofen and naproxen (analgesics), venlafaxine (antidepressant), and N,N-diethyl-meta-toluamide (insect repellant), were detected in all samples at all sites. Concentrations detected in the large specialty hospital outside the sewershed were similar to those within the sewershed. Cytotoxic drugs (tamoxifen and cyclophosphamide) and x-ray contrast media (iopamidol and diatrizoic acid) were infrequently detected in hospital effluents. Analysis for antibiotics indicated that azithromycin, clarithromycin, ciprofloxacin, erythromycin, ofloxacin, and sulfamethoxazole were consistently detected in hospital wastewaters, as was triclosan (antibacterial agent). Fifteen compounds individually contributed greater than 1% to the total PhAC and emerging contaminant load to the STP from the 2 hospitals in the sewershed, and 9 compounds in the STP effluent exceeded ecotoxicological criteria. The present survey demonstrates that point source discharges from healthcare facilities in this sewershed make a small contribution to the overall PhAC and emerging contaminant loading compared with the total concentrations entering the receiving STP. Environ Toxicol Chem 2015;9999:1–13. © 2015 SETAC

Saving a creek one bid at a time: A uniform price auction for urban stormwater retention

Abstract: Urban stormwater runoff degrades waterway health. We describe a market-based approach to identify the most efficient investments to reduce urban stormwater impacts at minimum cost. The framework involves the joint consideration of public and private supply of environmental services across scales; a metric to compare the benefits of interventions across and within scales; an environmental procurement auction to reveal and minimise the cost of private interventions; and an endogenous reserve price to select the optimal portfolio of investments. The paper discusses the economic and environmental rationale for the proposed approach, along with the results of Stormwater Tender, a field trial in Melbourne, Australia. To conceptualize the optimal portfolio of investments we draw the aggregate supply curve and the production possibility frontier (PPF) using data from the field trial. We find considerable heterogeneity in both the private and public cost of providing environmental benefits, highlighting the need t...

A Web-GIS Based Integrated Climate Adaptation Model

Abstract: 1 Waterway Ecosystem Research Group, School of Ecosystem and Forest Sciences, The University of Melbourne, Victoria, Australia 3121 2 Grace Detailed-GIS Services, 7 Arcadia Close, Taylors Lakes, Victoria, Australia 3038 Moroka Pty Ltd 4 Water Technology, 15 Business Park Drive, Notting Hill, Victoria, Australia 3168 Word Limit of the Paper should not be more than 3000 Words = 7/8 Pages) Abstract: Currently climate models exist as a desktop exercise in various formats and in a dis-integrated way. Any city with wide range of natural and cultural assets which make a major contribution to its liveability benefit greatly if various models and data can be accessed in an integrated way at any time using the Web to inform strategic response to climate change and variability, including: flood risk, river rise, sea level rise, extreme temperatures during heat waves, drought and subsequent reductions in soil moisture, and decline in tree health. There is a need to develop a decision support system that is spatially explicit and integrates various climate models into one visualisation environment to enable multi-criteria analysis to identify vulnerable areas and then to model possible interventions.

A practical tool for designing vegetated roofs to optimise rainfall retention

Abstract: Green roofs are increasingly being designed to reduce the volume of polluted stormwater generated by cities. Green roof designers therefore need tools to help them select an appropriate combination of plants and substrates which will maximise rainfall retention. The rainfall retention capacity and therefore the hydrological performance of green roofs are largely determined by the ability of plants to replenish the water storage capacity of the substrate between storm events. Most green roofs, however, are planted with drought-tolerant species with inherently low water use which, while limiting their rainfall retention capacity; ensures persistence of the vegetation during drought. In previous studies, we showed that plants from habitats analogous to green roofs, e.g., granite outcrops; can show adaptive water-use strategies; facilitating high water use when it is available, while retaining the ability to survive periods of drought. In this paper, we outline a simple green roof water balance model which describes how these alternative plant water-use strategies can affect the long-term hydrological performance of green roofs. The model allows the user to determine the best combination of substrates and plants to achieve given long-term runoff reduction targets; as well as quantifying the incidence and severity of drought stress. We intend to develop this model into a simple, user-friendly web application which can be used directly by urban planners and green roof designers.

Developing Australian green roofs: overview of a 5-year research program.

Abstract: Green or vegetated roofs are increasingly built in cities to provide multiple environmental and social benefits and are an emerging horticultural industry in Australia. Since 2008, researchers at the University of Melbourne s Burnley Campus have undertaken transdiciplinary research developing and evaluating green roofs for southern Australian conditions which are characterised by hot, dry summers. We have quantified plant performance through experiments on roofs and in controlled environments, using both Australian native and exotic species, to identify plant physiological and morphological traits that will improve green roof performance. We have developed lightweight mineral substrates based on scoria, bottom-ash from coal fired power stations and crushed roof tiles and evaluated water retention additives to improve water holding capacity and plant survival. Hydrology studies have found that 10-cm deep green roofs with scoria substrate can reduce stormwater runoff in Melbourne by 43-88%, depending on season and plant species. We found that a 12.5-cm deep green roof reduces building energy use by 38% in summer. Environmental psychology research demonstrates that people prefer green roofs with flowering meadow like vegetation and that viewing this type of green roof improves concentration and improves work performance. Our results have been embraced by the Australian green roof industry, resulting in construction of green roofs with our best performing substrates and plants and the development of science-based guidelines for future green roof projects.