Hydraulic Efficiency of Continuous Transverse Grates for Paved Areas

The hydraulic behavior of several continuous transverse gully grates is studied. Their use is common in some urban or impervious areas (squares, airport pavements, parks, pedestrian areas, etc.) where isolated inlets turn out to be ineffective in collecting the whole runoff into the sewer system during a storm event. Normally, manufacturers of such structures provide information about the bearing capacity, but little concerning their hydraulic behavior. Some grates with various widths were tested at the Technical University of Catalonia hydraulic laboratory for different approach flows and a large set of longitudinal slopes. Experimental equations were obtained to relate hydraulic efficiency of these structures to some relevant flow parameters such as the Froude number and the hydraulic depth. The first equation achieved may be used as a first approach to design a surface drainage system considering a constant circulating flow, whereas the second expression does not depend on flow values and could be used in storm-water and wastewater software packages to design surface drainage systems and for dual drainage modeling.     

Hydraulics of Tangential Vortex Intake for Urban Drainage

A tangential vortex intake is a compact structure that can convey storm water efficiently as a swirling flow down a vortex dropshaft. It has been studied in physical models and successfully employed in urban drainage and hydroelectric plant applications, but a comprehensive account of the key flow characteristics has not been reported and a theoretical design guideline of a tangential intake is not available. In this study the hydraulics of tangential slot vortex intakes is investigated via extensive experiments. It is found that the flow in the tapering and downward sloping vortex inlet channel is strongly dependent on the geometry of the inlet and dropshaft. Under some conditions, hydraulic instability and overflow can occur, rendering the design ineffective. It is shown that the hydraulic stability depends on the discharge at which flow control shifts from upstream to downstream (Qc), as well as the free drainage discharge (Qf). A theoretical design criterion for stable flow is developed in terms of Qf and Qc as a function of the vortex inlet geometry. For a “stable” design, the flow in the tapering inlet evolves from supercritical flow to subcritical flow smoothly as the discharge increases. Fifteen different tangential vortex intake models are tested. The experimental observations are in excellent agreement with the theoretical prediction. The present study provides a general guideline for designing a tangential vortex intake that can convey the flow smoothly without unstable fluctuating flow associated with a hydraulic jump.     

Model for Predicting Floods due to Earthen Dam Breaching. II: Comparison with Other Methods and Predictive Use

A sensitivity analysis of the model presented in the companion paper is made and, on the basis of the results a criterion is proposed for the choice of values to assign to the side slopes of the breach, in order to use the model for prediction. Moreover, the sensitivity analysis shows that the outflow hydrograph and its peak value depend not only on the dam height and the stored volume, but also on the vertical distribution of the water mass in the reservoir. The model is compared with some previously published methods and the disadvantages, limitations, and errors that can be made using parametric models and predictive equations are pointed out. Finally, easy to use equations interpolating the numerical results of the model are provided that predict not only the peak discharge but the whole outflow hydrograph for overtopping failures.     

Impact of Annual Average Daily Traffic on Highway Runoff Pollutant Concentrations

The objective of this study was to evaluate correlations between annual average daily traffic (AADT) and storm water runoff pollutant concentrations generated from California Department of Transportation (Caltrans) highway sites. Analyses of data collected from the Caltrans four-year (1997–2001) highway runoff characterization program revealed that, in general, pollutant concentrations from urban highways were higher than those found from nonurban highways. For a limited number of pollutants, however, the concentrations from nonurban highways were found to be higher than the concentrations from urban highways. No direct linear correlation was found between highway runoff pollutant event mean concentrations and AADT. However, through multiple regression analyses, it was shown that AADT has an influence on most highway runoff constituent concentrations, in conjunction with factors associated with watershed characteristics and pollutant build-up and wash off. The other noticeable factors shown to influence the accumulation of pollutants on highways were antecedent dry period, drainage area, maximum rain intensity, and land use.     

Rain Loads and Flow Attenuation on Roofs

Basic relationships are derived for calculating the flow attenuation and depth of storm water on roofs. Hyetographs and corresponding hydrographs are specialized to the case of roof drainage and incorporated in methods which are presented for analysis and design of roof drains. Roof storage and outflow are characterized for various roof geometries and outflow devices. The methods are applied to examples found in the literature, including those in standards of Factory Mutual Insurance Company, ASCE, and others. Assumptions implicit in those standards are tested and their limitations demonstrated. A critical duration at which the greatest water depth and outflow occur must be found on a case-by-case basis. The critical durations can differ significantly from the fixed durations specified in standards. The corresponding maximum water depths and peak outflows can also differ accordingly. For determination of roof loads, these results will have their greatest importance in warmer climates in which the rain loads govern over snow loads. An example of design specifically for flow attenuation is also presented.     

Evaluating Urban Pollutant Buildup/Wash-Off Models Using a Madison, Wisconsin Catchment

Buildup/wash-off (BUWO) models are widely used to estimate pollutant export from urban and suburban watersheds. Here, we propose that the mass of washed-off particulate during a storm event is insensitive to the time between storm events (the traditional predictor of particulate accumulation in BUWO models). Our analysis employed USGS data of total suspended solids and discharge data for nonsnow events in a 9.4-km2 suburban catchment in Madison, Wis. Kinetic energy of rainfall was calculated using National Weather Service NEXRAD radar reflectivity. A regression analysis found that storm event runoff volume and rainfall kinetic energy explained 81% of the variability in event particulate load; volume alone explained 69% of the variability in event loads. Time between storm events was not significant. Additionally, we simulated storm event particulate loads using a BUWO model and a model assuming a constant mass available for wash-off. Both models produced very similar predictions over a range of parameterizations, suggesting that buildup models could perhaps be simplified under many circumstances.     

拉盖尔函数应用于一般模型的辨识

研究并提出了当给定一个一般模型的维纳核时，其两个线性子系统的一种辨识方法，在这一方法中，对一般模型的两个线性子系统采用了拉盖尔函数作有限项级数展开的技巧。作为一种时域方法，它适用于非常广泛的一般模型构造。计算机模拟算例验证了该方法的正确性及有效性。     

Comparison of Models for Computing Drainage Discharge

The WAVE model describes the transport and transformations of matter and energy in the soil, crop, and vadose environment. A lateral field drainage subprogram was added to the WAVE model to simulate lateral subsurface drainage flow. The subsurface drainage is considered as the drainage provided by evenly spaced parallel drains with a free outlet: drain tubing or ditch. The rate of subsurface water movement into drain tubes or ditches depends on the hydraulic conductivity of the soil, drain or ditch spacing, hydraulic head in the drains, profile depth, and water table elevation. Hooghoudt's steady-state equation was selected for incorporation in the WAVE model. The subsurface drainage subprogram was calibrated and validated by comparison with the SWAP model (The Netherlands) and DRAINMOD (the United States) and partially by using 7 years of drain outflow data from an experimental field under fallow and cropped conditions. The comparative study revealed that the three models performed equally well and that the models were reliable and accurate tools for predicting the drainage flux as a function of rainfall-evapotranspiration and local conditions. The WAVE model, in comparison to the SWAP and DRAINMOD model, provided as good a prediction of the lateral subsurface drainage flow to drains. The statistical analysis between each model and observed data revealed that the three models were able to predict with sufficient accuracy the observed drainage discharge. The DRAINMOD model, however, has the advantage of giving a more accurate estimate of the discharge, resulting in a more precise modeling. The models were consistent in predicting water table levels, but they could not be verified against field data because of a lack of suitable measurements.     

Simultaneous Prediction of Saturated Hydraulic Conductivity and Drainable Porosity Using the Inverse Problem Technique

The saturated hydraulic conductivity K and the effective porosity f are two important input parameters needed for lateral drain spacing design, as well as some other applications. The technical and economic justification, of most drainage projects, is mainly connected to these two parameters. The current design procedure is based upon calculation of the lateral spacing, using some average values of K and f within the drainage area. The objectives of this study were to introduce a new method for simultaneous estimation of K and f parameters using the inverse problem technique, and to evaluate five different unsteady drainage analytical models of the Boussinesq equation, suggested by different researchers for simultaneous prediction of the parameters. Consequently, five different analytical models for predicting water table profiles were solved, using the inverse problem technique. Each model was then evaluated. A physical drainage model of 2.2?m length, 0.3?m width, and 0.5?m height was established in the laboratory and carefully packed with a sandy loam soil. A perforated drainage pipe of 4.5?cm in diameter was installed at the bottom end of the model. Many piezometers were inserted in the soil for spatial and temporal water table monitoring. Different data sets from the experiments and literature were used for model calibration. The newly proposed approach that is based upon measuring water table profiles, at different times, was then evaluated with both constant and variable f. The predicted values of the proposed approach indicated reasonable agreement with the measured data. With variable effective porosity, the method was even more accurate to predict the water table profiles. Using the inverse problem technique, all the analytical models provided good agreement with the measured data. Among these, however, the Topp and Moody model predicted more accurate results than other models.     

城市暴雨内涝情景模拟与灾害风险评估

Scenado modelling and the risk assessment of natural disasters is one of the hot-spots in disaster research. However, up until now, urban natural disaster risk assessments lack common procedures and programmes. This paper selects rainstorm waterlogging as a disaster to research, which is one of the most frequently occurring hazards for most cities in China. As an example, we used a small-scale integrated methodology to assess risks relating to rainstorm waterlogging hazards in the Jing'an District of Shanghai. Based on the basic concept of disaster risk, this paper applies scenario modelling to express the risk of small-scale urban rainstorm waterlogging disasters in different return periods. Through this analysis of vulnerability and exposure, we simulate different disaster scenarios and propose a comprehensive analysis method and procedure for small-scale urban storm waterlogging disaster risk assessments. A grid-based Geographical Information System (GIS) approach,including an urban terrain model, an urban rainfall model and an urban drainage model, was applied to simulate inundation area and depth. Stage-damage curves for residential buildings and contents were then generated by the loss data of waterlogging from field surveys, which were further applied to analyse vulnerability, exposure and loss assessment. Finally, the ex-ceedance probability curve for disaster damage was constructed using the damage of each simulated event and the respective exceedance probabilities. A framework was also devel-oped for coupling the waterlogging risk with the risk planning and management through the exceedance probability curve and annual average waterlogging loss. This is a new explora-tion for small-scale urban natural disaster scenario simulation and risk assessment.     

The overparameterized analysis of variance model.

Analyses of variance (ANOVA) with the general linear model (OLM) in many standard statistical packages use an overparameterized model, a model unfamiliar to most behavioral science researchers. Estimates and significance tests with GLM procedures are calculated by computing generalized inverses and estimates of estimable functions. Using simple examples, the authors discuss the concepts that underlie the solutions for 1-way and 2-way ANOVAs with overparameterized models and illustrate how these models allow one to evaluate the research hypotheses. The authors also extend the discussion of overparameterized models to a more general modeling approach than GLM, the general linear mixed model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Minimizing the Ecological Risk of Combined-Sewer Overflows in an Urban River System by a System-Based Approach

As urban and suburban areas expand, the problem of sewage disposal spreads as well. Inappropriate planning of a sewage management system could impair water quality, destroy habitat, and threaten public health. Simply building a sewage interceptor system along the urban river corridor to handle the wastewater effluents without regard to the impacts from combined-sewer overflows (CSOs) in the storm events cannot fulfill the ultimate goal of environmental restoration in the receiving water body. This study therefore carries out a system-based assessment to search for the optimal operating strategy of the interceptor facilities with respect to biocomplexity or biodiversity in an urban river system. In particular, it focuses on the richness of the fish community in the biological systems, the effect of stress on the fish community by storm events, and their capacity for adaptive behavior in response to the CSOs’ impact in the Love River estuarine system, South Taiwan. By integrating the biological indicators in an environmental context, two simulation models describing the quality and quantity of storm water and their impact on the river water quality are calibrated and verified. The interactions of natural systems and engineered systems covering both spatial and temporal aspects can then be explored in terms of the predicted levels of dissoved oxygen (DO) along the river reaches so as to strengthen an ultimate optimal search for the best operational alternative for the interceptor system. In view of the inherent complexity of integrating simulation outputs at various scales to aid in building the optimization step, three regression submodels were derived beforehand. These submodels present a high potential for exhibiting, eliciting, and summarizing the nonlinear behavior between the CSO impacts and the DO levels in the river reaches. With the aid of such findings, this study finally applies a linear programming model to determine the optimal size of a constructed storage pond (i.e., a detention pond), based on several types of storm events in the study area. This is proved essential for minimizing the ecological risk in such a way so as to indirectly improve the biodiversity in the estuarine river system.     

GIS Based Distributed Model for Soil Erosion and Rate of Sediment Outflow from Catchments

A spatially distributed rainfall–runoff–soil erosion model capable of handling catchment heterogeneity in terms of landuse, soil, slope, and rainfall has been developed and applied to data from several catchments. The model operates on a cell basis and accepts distributed inputs from a raster geographic information system (GIS). The catchment digital elevation model is used in the model to generate drainage paths from each of the discretized cells to the catchment outlet in proper hydrologic order. Following the computational hydrological sequencing thus derived, the mechanics of overland flow are modeled using a finite volume based numerical solution of the diffusion wave approximation of the St. Venant equations and the process of soil erosion is modeled using a numerical solution of the sediment continuity equation with appropriate auxiliary equations. The spatial information for each cell of the catchment was generated using digital analysis of satellite data and published information by making use of commercially available image processing and raster GIS packages. Results of model application on several catchments indicate that the model can compute temporal distribution of the sediment outflow rate at the catchment outlet for storm events reasonably well. The cell-based structure of the model also allows for computation of the spatial distribution of computed variables such as the amount of soil erosion.     

Hydraulic Model for Sedimentation in Storm-Water Detention Basins

Treatment of storm-water runoff may be necessary before discharge to surface waters. In urban areas, space constraints limit selection of conventional treatment systems, and alternative systems are needed. This research program involves design and laboratory testing of a small footprint nonproprietary detention basin which consists of pipes and box culvert sections with a specialized inlet and outlet system. This system can be placed below grade near the roadway section as part of the conventional drainage system and does not require additional right-of-way. A mathematical model, based entirely on hydraulic principles, is developed to estimate particle removal efficiency of the rectangular detention basin for the treatment of storm-water runoff by extending ideal horizontal tank theory under the condition in which water level is varied. A physical model was built in 1/5 scale to measure particle removal performance and validates the conceptual model. Experiments were performed for steady inflow conditions with different inflow rates, durations, and suspended sediment concentrations. Measured time series outflow suspended sediment concentrations and particle removal efficiency compare well with calculated results from the conceptual model. The outflow particle-size distribution can also be estimated using the conceptual model.     

Level A in vivo-in vitro correlation: nonlinear models and statistical methodology

Some new nonlinear models for the relationship between the fraction of drug dose dissolved (absorbed) in vivo and that dissolved in vitro are described. The models are empirical in nature and are generalizations of the linear model that, at present, is the most commonly used model. The modeling approach is based on considering the time at which a drug molecule goes into solution (in vitro or in vivo) to be a random variable and relating the distribution functions using proportional odds, proportional hazards, and proportional reversed hazards models. The models are further extended by allowing the parameter that relates in vivo and in vitro to be a function of time. A statistical model for the data is developed and used as the basis for a statistical methodology for fitting these models. The methods are shown to be generalized linear mixed effects model (GLMM) methods. The models are fitted to some data sets, and the results demonstrate that these models have potential.     

Model Selection Using Response Measurements: Bayesian Probabilistic Approach

A Bayesian probabilistic approach is presented for selecting the most plausible class of models for a structural or mechanical system within some specified set of model classes, based on system response data. The crux of the approach is to rank the classes of models based on their probabilities conditional on the response data which can be calculated based on Bayes’ theorem and an asymptotic expansion for the evidence for each model class. The approach provides a quantitative expression of a principle of model parsimony or of Ockham’s razor which in this context can be stated as “simpler models are to be preferred over unnecessarily complicated ones.” Examples are presented to illustrate the method using a single-degree-of-freedom bilinear hysteretic system, a linear two-story frame, and a ten-story shear building, all of which are subjected to seismic excitation.     

Locating Discharge Trajectories in Still and Moving Ambient Fluids

The angular momentum principle is employed to locate the trajectories of wastewater plumes. This momentum-based method differs from the traditional approach where a perturbation analysis, based on the centerline velocities, is employed for locating discharges. Evidence of the latter can be found in existing Eulerian-integral and length-scale models. The momentum-based method is incorporated into the hybrid model SD3D, where the regional flow solutions are modified to incorporate the influences of relatively small components of momentum on the discharge trajectory. This method provides a clear understanding of the factors that influence the location of the discharge. The momentum-based approach yields analytical trajectory solutions in many cases, and it eliminates the need to arbitrarily select the appropriate characteristic velocity for locating the flow. Comparisons are made with available experimental data, and they show that the momentum-based method provides accurate predictions of the flow trajectories under a variety of discharge conditions. Comparisons are also made with predictions from the CORMIX1 and JETLAG models. In general the predictions are consistent, but some important discrepancies are highlighted. The use of the momentum-based method for locating discharges is discussed in light of recent experimental studies.     

Optimal Layout of Sewer Systems: A Deterministic versus a Stochastic Model

The optimization of a new or partially existing urban drainage system may be modeled as a subproblems sequence of layout and optimal design within the discrete search space. The design optimization, incorporating the optimal selection of the pumping stations, intermediate manholes, pipe sections, and installation depths, for a general system fixed layout in plan, is a high level sequential decision problem which may be efficiently solved deterministically through a multilevel dynamic programming model. The optimal general layout may be selected in a deterministic way by means of a simple economical comparison of all plan solutions having optimized designs, for small to medium sized systems (if the specific restrictions of the applications are appropriately exploited) in practicable computer time. For larger dimension networks, where it is clearly impossible to achieve plan optimization with full enumeration (which is a NP complete), stochastic search models can be used. For the subproblem layout, an effective enumeration model is presented; the results of a stochastic model proposed previously, using simulated annealing for an application example, are compared and discussed in detail.     

Mixed-effects logistic regression for estimating transitional probabilities in sequentially coded observational data.

This article demonstrates the use of mixed-effects logistic regression (MLR) for conducting sequential analyses of binary observational data. MLR is a special case of the mixed-effects logit modeling framework, which may be applied to multicategorical observational data. The MLR approach is motivated in part by G. A. Dagne, G. W. Howe, C. H. Brown, & B. O. Muthén (2002) advances in general linear mixed models for sequential analyses of observational data in the form of contingency table frequency counts. The advantage of the MLR approach is that it circumvents obstacles in the estimation of random sampling error encountered using Dagne and colleagues' approach. This article demonstrates the MLR model in an analysis of observed sequences of communication in a sample of young adult same-sex peer dyads. The results obtained using MLR are compared with those of a parallel analysis using Dagne and colleagues' linear mixed model for binary observational data in the form of log odds ratios. Similarities and differences between the results of the 2 approaches are discussed. Implications for the use of linear mixed models versus mixed-effects logit models for sequential analyses are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design of a Scroll Vortex Inlet for Supercritical Approach Flow

Vortex drop shafts are used in urban drainage systems to connect two sewers located at considerably different elevations. After their introduction in 1947, these were studied with particular reference to subcritical approach flow. Vortex shafts for supercritical approach flow can also be used, but the intake structure may have relatively high cost due to the complex geometry. The present study includes experimental results of a specific investigation on the changes to be made in the supercritical approach channel if a subcritical vortex intake is used. The experimental investigation analyzes the effect of a hydraulic jump on the performance of vortex intake structure to define appropriate technical solutions, essentially consisting in a negative step to be located along the supercritical approach channel. Design criteria are finally presented for the evaluation of the step height and its distance from the vortex intake structure.