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Modeling the hydrologic effects of watershed-scale green roof implementation in the Pacific Northwest, United States.

ABSTRACT: Green roofs are among the most popular type of green infrastructure implemented in highly urbanized watersheds due to their low cost and efficient utilization of unused or under-used space. In this study, we examined the effectiveness of green roofs to attenuate stormwater runoff across a large metropolitan area in the Pacific Northwest, United States. We utilized a spatially explicit ecohydrological watershed model called Visualizing Ecosystem Land Management Assessments (VELMA) to simulate the resulting stormwater hydrology of implementing green roofs over 25%, 50%, 75%, and 100% of existing buildings within four urban watersheds in Seattle, Washington, United States. We simulated the effects of two types of green roofs: extensive green roofs, which are characterized by shallow soil profiles and short vegetative cover, and intensive green roofs, which are characterized by deeper soil profiles and can support larger vegetation. While buildings only comprise approximately 10% of the total area within each of the four watersheds, our simulations showed that 100% implementation of green roofs on these buildings can achieve approximately 10-15% and 20-25% mean annual runoff reductions for extensive and intensive green roofs, respectively, over a 28-year simulation. These results provide an upper limit for volume reductions achievable by green roofs in these urban watersheds. We also showed that stormwater runoff reductions are proportionately smaller during higher flow regimes caused by increased precipitation, likely due to the limited storage capacity of saturated green roofs. In general, green roofs can be effective at reducing stormwater runoff, and their effectiveness is limited by both their areal extent and storage capacity. Our results showed that green roof implementation can be an effective stormwater management tool in highly urban areas, and we demonstrated that our modeling approach can be used to assess the watershed-scale hydrologic impacts of the widespread adoption of green roofs across large metropolitan areas.

SUBMITTER: Barnhart B

PROVIDER: S-EPMC8237799 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Cryptococcus gattii is a fungal pathogen causing an emerging outbreak in the United States Pacific Northwest (PNW). Treatment guidelines for cryptococcosis are primarily based on data from C. neoformans infections; applicability to PNW C. gattii infection is unknown. We evaluated the relationship between initial antifungal treatment and outcomes for PNW C. gattii patients. METHODS: Cases were defined as culture-confirmed invasive C. gattii infections among residents of Oregon and Washington States during 2004-2011. Clinical data were abstracted from medical records through one year of follow-up. Recommended initial treatment for central nervous system (CNS), bloodstream, and severe pulmonary infections is amphotericin B and 5-flucytosine; for non-severe pulmonary infections, recommended initial treatment is fluconazole. Alternative initial treatment was defined as any other initial antifungal treatment. RESULTS: Seventy patients survived to diagnosis; 50 (71%) received the recommended initial treatment and 20 (29%) received an alternative. Fewer patients with pulmonary infections [21 (64%)] than CNS infections [25 (83%)] received the recommended initial treatment (p = 0.07). Among patients with pulmonary infections, those with severe infections received the recommended initial treatment less often than those with non-severe infections (11% vs. 83%, p<0.0001). Eight patients with severe pulmonary infections received alternative initial treatments; three died. Four patients with non-severe pulmonary infections received alternative initial treatments; two died. There was a trend towards increased three-month mortality among patients receiving alternative vs. recommended initial treatment (30% vs. 14%, p = 0.12), driven primarily by increased mortality among patients with pulmonary disease receiving alternative vs. recommended initial treatment (42% vs. 10%, p = 0.07). CONCLUSIONS: C. gattii patients with pulmonary infections--especially severe infections--may be less likely to receive recommended treatment than those with CNS infections; alternative treatment may be associated with increased mortality. Reasons for receipt of alternative treatment among C. gattii patients in this area should be investigated, and clinician awareness of recommended treatment reinforced.

Project description:Watershed integrity is the capacity of a watershed to support and maintain the full range of ecological processes and functions essential to sustainability. Using information from EPA's StreamCat dataset, we calculated and mapped an Index of Watershed Integrity (IWI) for 2.6 million watersheds in the conterminous US with first-order approximations of relationships between stressors and six watershed functions: hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity, temperature regulation, and habitat provision. Results show high integrity in the western US, intermediate integrity in the southern and eastern US, and the lowest integrity in the temperate plains and lower Mississippi Valley. Correlation between the six functional components was high (r = 0.85-0.98). A related Index of Catchment Integrity (ICI) was developed using local drainages of individual stream segments (i.e., excluding upstream information). We evaluated the ability of the IWI and ICI to predict six continuous site-level indicators with regression analyses - three biological indicators and principal components derived from water quality, habitat, and combined water quality and habitat variables - using data from EPA's National Rivers and Streams Assessment. Relationships were highly significant, but the IWI only accounted for 1-12% of the variation in the four biological and habitat variables. The IWI accounted for over 25% of the variation in the water quality and combined principal components nationally, and 32-39% in the Northern and Southern Appalachians. We also used multinomial logistic regression to compare the IWI with the categorical forms of the three biological indicators. Results were consistent: we found positive associations but modest results. We compared how the IWI and ICI predicted the water quality PC relative to agricultural and urban land use. The IWI or ICI are the best predictors of the water quality PC for the CONUS and six of the nine ecoregions, but they only perform marginally better than agriculture in most instances. However, results suggest that agriculture would not be appropriate in all parts of the country, and the index is meant to be responsive to all stressors. The IWI in its present form (available through the StreamCat website; https://www.epa.gov/national-aquatic-resource-surveys/streamcat) could be useful for management efforts at multiple scales, especially when combined with information on site condition. The IWI could be improved by incorporating empirical or literature-derived relationships between functional components and stressors. However, limitations concerning the absence of data for certain stressors should be considered.

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Modeling the hydrologic effects of watershed-scale green roof implementation in the Pacific Northwest, United States.

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