Estimating Flood Frequency in Gaged and Ungaged Watersheds

Proceedings of the 1999 Georgia Water Resources Conference, March 30 and 31, Athens, Georgia.Estimation of flood frequency is important in jurisdictional wetlands determination and functional assessment, stream classification and restoration, and in assessing urban and agricultural risk in flood prone areas. For example, in utilizing the hydrogeomorphic approach (HGM) for wetland functional assessment for riverine wetlands, the flood frequency variable is required in seven of the suite of fifteen functions. However, site-specific determination of flood frequency has been difficult, especially in ungaged watersheds. One promising method is development of regional dimensionless rating curves. The curves are derived from stage/discharge and channel geometric relationships associated with gaged watersheds. Once the curves are constructed and calibrated to a specific region, flood frequency and channel geometry can be estimated at any point within ungaged as well as gaged watersheds within that region. This method was employed to calibrate the flood frequency variable in the low gradient, riverine HGM guidebook applicable to Western Kentucky. Flood frequency and discharge were determined at several riverine reference wetlands for the purpose of assessing wetland function throughout the Western Kentucky Coalfield Physiographic Region.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202 with partial funding provided by the U.S. Department of Interior, geological Survey, through the Georgia Water Research Insttitute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-397). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors

Agriculture, food security and climate change: Outlook for knowledge, tools and action

Agriculture and food security are key sectors for intervention under climate change. Agricultural production is highly vulnerable even to 2C (lowend) predictions for global mean temperatures in 2100, with major implications for rural poverty and for both rural and urban food security. Agriculture also presents untapped opportunities for mitigation, given the large land area under crops and rangeland, and the additional mitigation potential of aquaculture. This paper presents a summary of current scientific knowledge on the impacts of climate change on farming and food systems, and on the implications for adaptation and mitigation. Many of the trends and impacts are highly uncertain at a range of spatial and temporal scales; we need significant advances in predicting how climate variability and change will affect future food security. Despite these uncertainties, it is clear that the magnitude and rate of projected changes will require adaptation. Actions towards adaptation fall into two broad overlapping areas: (1) better management of agricultural risks associated with increasing climate variability and extreme events, for example improved climate information services and safety nets, and (2) accelerated adaptation to progressive climate change over decadal time scales, for example integrated packages of technology, agronomy and policy options for farmers and food systems. Maximization of agriculture’s mitigation potential will require, among others, investments in technological innovation and agricultural intensification linked to increased efficiency of inputs, and creation of incentives and monitoring systems that are inclusive of smallholder farmers. The challenges posed by climate change to agriculture and food security require a holistic and strategic approach to linking knowledge with action. Key elements of this are greater interactions between decision-makers and researchers in all sectors, greater collaboration among climate, agriculture and food security communities, and consideration of interdependencies across whole food systems and landscapes. Food systems faced with climate change need urgent action in spite of uncertainties

Which clinical research questions are the most important?:Development and preliminary validation of the Australia & New Zealand Musculoskeletal (ANZMUSC) Clinical Trials Network Research Question Importance Tool (ANZMUSC-RQIT)

Background and aimsHigh quality clinical research that addresses important questions requires significant resources. In resource-constrained environments, projects will therefore need to be prioritized. The Australia and New Zealand Musculoskeletal (ANZMUSC) Clinical Trials Network aimed to develop a stakeholder-based, transparent, easily implementable tool that provides a score for the 'importance' of a research question which could be used to rank research projects in order of importance.MethodsUsing a mixed-methods, multi-stage approach that included a Delphi survey, consensus workshop, inter-rater reliability testing, validity testing and calibration using a discrete-choice methodology, the Research Question Importance Tool (ANZMUSC-RQIT) was developed. The tool incorporated broad stakeholder opinion, including consumers, at each stage and is designed for scoring by committee consensus.ResultsThe ANZMUSC-RQIT tool consists of 5 dimensions (compared to 6 dimensions for an earlier version of RQIT): (1) extent of stakeholder consensus, (2) social burden of health condition, (3) patient burden of health condition, (4) anticipated effectiveness of proposed intervention, and (5) extent to which health equity is addressed by the research. Each dimension is assessed by defining ordered levels of a relevant attribute and by assigning a score to each level. The scores for the dimensions are then summed to obtain an overall ANZMUSC-RQIT score, which represents the importance of the research question. The result is a score on an interval scale with an arbitrary unit, ranging from 0 (minimal importance) to 1000. The ANZMUSC-RQIT dimensions can be reliably ordered by committee consensus (ICC 0.73-0.93) and the overall score is positively associated with citation count (standardised regression coefficient 0.33, pConclusionWe propose that the ANZMUSC-RQIT is a useful tool for prioritising the importance of a research question

Mechanisms of impulsive choice: I. Individual differences in interval timing and reward processing

Impulsive choice behavior incorporates the psychological mechanisms involved in the processing of the anticipated magnitude and delay until reward. The goal of the present experiment was to determine whether individual differences in such processes related to individual differences in impulsive choice behavior. Two groups of rats (Delay Group and Magnitude Group) were initially exposed to an impulsive choice task with choices between smaller-sooner (SS) and larger-later (LL) rewards. The Delay Group was subsequently exposed to a temporal discrimination task followed by a progressive interval task, whereas the Magnitude Group was exposed to a reward magnitude sensitivity task followed by a progressive ratio task. Inter-task correlations revealed that the rats in the Delay Group that made more self-controlled (LL) choices also displayed lower standard deviations in the temporal bisection task and greater delay tolerance in the progressive interval task. Impulsive choice behavior in the Magnitude Group did not display any substantial correlations with the reward magnitude sensitivity and progressive ratio tasks. The results indicate the importance of core timing processes in impulsive choice behavior, and encourage further research examining the effects of changes in core timing processes on impulsive choice

Analytical and experimental study of flow from a slot into a freestream

The fluid mechanics of a jet issuing from a slot into a freestream is studied analytically and experimentally. The analytic study assumes incompressible, inviscid, irrotational flow for both the jet and freestream as well as equal stagnation pressures. The analysis proceeds by means of potential flow theory, using the Helmholtz-Kirchoff method of mapping the physical flow onto a simpler domain. This method examines the relationships between the geometrical and velocity parameters. Theoretical results for the mass flow out of the slot, shape of the streamline which divides the injectant from the mainstream, the coefficient of pressure across the slot, the velocity field across the slot and the coefficient of discharge from the slot are found for various slot angles. The calculated flow rates and coefficients of discharge are compared with data obtained from experiments performed using air flowing from a plenum, through a slot, into a small wind tunnel. The calculated and measured flow rates give similar trends and agree within ±17%. Differences are due to experimental uncertainties and the neglect in the theory of downstream flow separation and subsequent reattachment, upstream boundary layer thickness, or turbulent mixing along the dividing streamline. Despite these differences, the gross influence of the mainstream on the mass flow from the jet compares well. The effect of unequal stagnation pressures in the jet and mainstream is investigated experimentally and found to be smaller than the effect of changing geometry. The general agreement between theory and experiment suggests that pressure effects control the overall flow rate to a large extent and that this model can serve as a skeletal study for slot flow.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat

A photochemical model based on a scaling analysis of ozone photochemistry

A scaling-level model of a photochemical mechanism has been developed and integrated into an air quality model used to study ozone formation in an urban environment. A scaling analysis was used to capture the internal workings of a photochemical mechanism using the OZIPR trajectory model to simulate a smog chamber for a wide range of precursor concentrations and a variety of environmental conditions. The Buckingham P i method of dimensional analysis was used to express the relevant variables in terms of dimensionless groups. These grouping show maximum ozone, initial NOx and initial VOC concentrations to be made non-dimensional by the average NO₂ photolysis rate (j[sub av]) and the rate constant for the NO-O3 titration reaction ([sup k]NO); temperature by the NO-O₃ activation energy (E/R) and time by the cumulative NO₂ photolysis rate (J). The analysis shows dimensionless maximum ozone concentration can be described by a product of powers of dimensionless initial NOx concentration, dimensionless temperature (θ(T)) and a similarity curve (f) directly dependent on the ratio of initial VOC to NOx concentration (R) and internally dependent on the cumulative NO₂ photolysis rate: [Chemical Equation Diagram] When Weibull transformed, the dimensionless model output cluster onto two line segments. This is interpreted as-a break in ..the scaling and can be understood,in-terms of a change in governing feedback mechanisms separating low- and high-NOx chemistry regimes. The similarity relationship can be modeled by two Weibull distributions using four parameters: two describing the slopes of the line segments (01,02) and two giving the location of their intersection (β, λ): [Chemical Equation Diagram] A fifth parameter (γ) is used to normalize the model output. The most important parameter, β, the VOC to NOx ratio at the scaling break, defines a characteristic process scale for ozone photochemistry. The scaling analysis, similarity curve and parameterization appear to be independent of the details of the chemical mechanism, hold for a variety of VOC species and mixtures and are applicable over a wide range of VOC and NOx concentrations. The similarity relationship is used to generalize ozone-precursor relationships in terms of four rules governing ozone production (P(O₃)), to quantify NOx-inhibition and define isopleth slope. The scaling framework is used to study VOC reactivity, explore the scaling properties of a simple reaction mechanism and collapse a wide range of smog chamber measurements onto a single similarity curve. To complement the scaling analysis, a meteorological model and an emissions inventory were developed. These were incorporated into an air quality model used to explore the sensitivity of a regional ozone plume to environmental conditions, and precursor .concentrations. The air quality model consisted of a series of box models being advected by the mean wind, for a single day, where photochemistry of the precursors emissions was modeled using the similarity relationships developed from the scaling analysis. The chosen domain was the Lower Fraser Valley B.C., a complex coastal region that experiences moderate ozone episodes during summertime fair-weather conditions. Emission fields were developed using published emission totals, four land-use categories and generic temporal emissions curves and were found to be comparable with fields based on more detailed inventories. Wind observations (speed and direction), from 53 stations, on a typical episode day, were interpolated to produce hourly wind fields. Mixing depths were determined using a simple slab model incorporating the interpolated wind fields and measured heat fluxes. The most problematic aspect of the model was determining the effects of pollutant build up in the boundary layer, prior to the modeling day. This was handled by emitting precursors into the boundary layer and advecting them, without chemical reactions, until steady state concentrations were reached. These were dependent on the choice of background concentrations used to initialize the pre-conditioning scheme and were set so resulting boundary layer NOx and VOC concentrations were in agreement with the limited available data and peak ozone concentrations were typical of recent episodes. In departure from previous modeling studies, model validation was not through point by point analysis of model output and observations but through high level comparison of model sensitivity with a range of modeling techniques and observations. The model appears to capture ozone sensitivity to meteorological conditions and precursor concentrations; justifying its use as a screening tool. The model suggests: the region to be VOC limited; projected emissions reductions may not improve present episodic ozone concentrations; larger than anticipated reductions in NOx emissions, without equivalent additional VOC reductions, could increase episodic concentrations and future emissions reductions, stemming from TIER 2 LDV standards, which target NOx emissions to a greater extent than VOC emissions, may not result in appreciable changes in episodic ozone concentrations. These conclusions are intended to guide comprehensive modeling studies.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat

Spatiotemporal Trends in Episodic Ozone Pollution in the Lower Fraser Valley, British Columbia, in Relation to Mesoscale Atmospheric Circulation Patterns and Emissions.

A cluster analysis of wind measurements from two meteorological stations in the Lower Fraser Valley, British Columbia, Canada, has been performed to identify mesoscale circulation regimes that are common to days on which ozone mixing ratios at one or more measuring stations in the region’s fixed monitoring network exceed the National Ambient Air Quality Objective of 82 ppb. The analysis, using 20 yr of data (1984–2003), identifies the following four regimes: two with morning winds at the coastal Vancouver International Airport (YVR) meteorological station from the northwest direction and two with southerly YVR morning winds. Not all exceedance days are associated with sea-breeze circulations, but days with southerly morning winds have a higher proportion of well-developed sea-breeze circulations. Composite synoptic patterns associated with each regime all show high pressure over the eastern Pacific Ocean with a thermal trough over Washington State and southwestern British Columbia. Composite ozone patterns, corresponding to each mesoscale circulation regime and taken at the hour of maximum ozone concentration, show similar general features, including strong ozone titration in and around the urban source regions and higher values downwind. This suggests that precursor buildup, prior to the exceedance day, plays an important role in the spatial ozone pattern on exceedance days. A simple multiple linear regression of the plume centroid with the number of days elapsed from the start of the analysis period suggests the centroid of the ozone plume has shifted eastward since 1990. There also appears to be a north–south shift in the ozone plume. It is impossible to tell if these shifts are due to changes in emission levels or to changes in spatial emission patterns, because both changes have occurred over the study period. Copyright 2007 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or [email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult

Simple Model for Pollution Dispersion in a Convective Boundary Layer.

A simplified model for dispersion in a convective boundary layer is presented and is used to diagnose crosswind-integrated concentrations, ground-level concentrations, and vertical plume spread over flat terrain for various release heights. The model parameterizes the long-wavelength oscillation of the time-averaged plume centerline versus downwind distance under unstable conditions, using a simple sine wave. This wave is phase shifted to account for the influence of source height and is damped toward the mid–mixed layer to account for the well-mixed end state of convective dispersion. This model represents an improvement over a previous model in two ways. First, vertical dispersion about the oscillating time-averaged centerline is parameterized using a lognormal distribution instead of a Gaussian distribution so as to give better ground-level concentration. Second, to account for the addition of surface-layer shear-generated turbulence to a convective boundary layer, the wavelength of the time-averaged oscillation is stretched as a function of the ratio of friction velocity to the Deardorff convective velocity scale. Results are tested against published laboratory, large-eddy simulation, and field data and are compared with the dispersion scheme used in the AERMOD regulatory dispersion model. In general, the simplified convective dispersion model provides close agreement with the observations and simulations. The utility of a buoyancy velocity to serve as a convection scale is also demonstrated. Copyright 2006 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or [email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult

The Scaling Law Relating World Point-Precipitation Records to Duration.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

Retrospective analysis of ozone formation in the Lower Fraser Valley, B. C.

Science, Faculty ofEarth and Ocean Sciences, Department ofUnreviewedFacult