Experimental Investigation Of Flow-Interactions Between Above And Below Ground Drainage Systems Through A Manhole

The frequency, magnitude and impact of pluvial flooding events both in the UK and worldwide is forecast to increase due to: climate change (Butler and Davies 2011), the effects of urbanisation and urban creep (Semadeni‐Davies et al 2008) as well as aging drainage infrastructure (Ashley et al. 2004). Pluvial flood models (e.g. Leandro et al. 2008) are increasingly being used to assess flood risk, develop asset investment strategies and develop surface water management plans. However due to the nature of urban flood events, it is very difficult to calibrate and validate such pluvial flood models. In particular the rate of exchange between above and below ground systems is a source of considerable uncertainty in urban flood modelling (Djordjević et al, 2005). This work utilises a unique surface/subsurface model (as described in Rubinato et al. 2012a, and Rubinato et al. 2012b) at the University of Sheffield. The model consists of a pipe drainage network linked via a manhole to an urban surface with a slope 1:1000. Inflow and outflow to the above and below ground systems can be controlled and monitored independently in real time. The specific objective of this work is: - Experimentally quantify the interaction of flow between the below and above ground systems for a range of pluvial flooding conditions. Water depth, flow rate will be measured in real time and initial results on exchange rate between the below system and the urban surface will be quantified and compared to commonly used energy loss equations with the determination of specific coefficients (free weir linkage; submerged weir linkage and orifice linkage). The overall aim of the research is to improve urban pluvial flood models and a more accurate understanding of the hydraulic characteristics of interaction points and to quantify surface flow paths

Experimental calibration and validation of sewer/surface flow exchange equations in steady and unsteady flow conditions

This is the final version of the article. Available from Elsevier via the DOI in this record.The linkage between sewer pipe flow and floodplain flow is recognised to induce an important source of uncertainty within two-dimensional (2D) urban flood models. This uncertainty is often attributed to the use of empirical hydraulic formulae (the one-dimensional (1D) weir and orifice steady flow equations) to achieve data-connectivity at the linking interface, which require the determination of discharge coefficients. Because of the paucity of high resolution localised data for this type of flows, the current understanding and quantification of a suitable range for those discharge coefficients is somewhat lacking. To fulfil this gap, this work presents the results acquired from an instrumented physical model designed to study the interaction between a pipe network flow and a floodplain flow. The full range of sewer-to-surface and surface-to-sewer flow conditions at the exchange zone are experimentally analysed in both steady and unsteady flow regimes. Steady state measured discharges are first analysed considering the relationship between the energy heads from the sewer flow and the floodplain flow; these results show that existing weir and orifice formulae are valid for describing the flow exchange for the present physical model, and yield new calibrated discharge coefficients for each of the flow conditions. The measured exchange discharges are also integrated (as a source term) within a 2D numerical flood model (a finite volume solver to the 2D Shallow Water Equations (SWE)), which is shown to reproduce the observed coefficients. This calibrated numerical model is then used to simulate a series of unsteady flow tests reproduced within the experimental facility. Results show that the numerical model overestimated the values of mean surcharge flow rate. This suggests the occurrence of additional head losses in unsteady conditions which are not currently accounted for within flood models calibrated in steady flow conditions.The research has been supported by the UK Engineering and Physical Sciences Research Council (grants ID: EP/K040405/1)

Predicting combined sewer overflows chamber depth using artificial neural networks with rainfall radar data

Combined sewer overflows (CSOs) represent a common feature in combined urban drainage systems and are used to discharge excess water to the environment during heavy storms. To better understand the performance of CSOs, the UK water industry has installed a large number of monitoring systems that provide data for these assets. This paper presents research into the prediction of the hydraulic performance of CSOs using artificial neural networks (ANN) as an alternative to hydraulic models. Previous work has explored using an ANN model for the prediction of chamber depth using time series for depth and rain gauge data. Rainfall intensity data that can be provided by rainfall radar devices can be used to improve on this approach. Results are presented using real data from a CSO for a catchment in the North of England, UK. An ANN model trained with the pseudo-inverse rule was shown to be capable of providing prediction of CSO depth with less than 5% error for predictions more than one hour ahead for unseen data. Such predictive approaches are important to the future management of combined sewer systems

Validation of 2D shock capturing flood models around a surcharging manhole

This work offers a detailed validation of finite volume (FV) flood models in the case where horizontal floodplain flow is affected by sewer surcharge flow via a manhole. The FV numerical solution of the 2D shallow water equations is considered based on two approximate Riemann solvers, HLLC and Roe, on both quadrilateral structured and triangular unstructured mesh-types. The models are validated against a high resolution experimental data-set obtained using a physical model of a sewer system linked to a floodplain via a manhole. It was verified that the sensitivity of the models is inversely proportional to the surcharged flow/surface inflow ratio, and therefore requires more calibration from the user especially when concerned with localised modelling of sewer-to-floodplain flow. Our findings provide novel evidence that shock capturing FV-based flood models are applicable to simulate localised sewer-to-floodplain flow interaction

Investigating the microbiological risks associated with urban flooding in the UK

Over the last 30 years, the frequency and occurrence of intense rainfall, and thus extreme hydrological events –flooding- has steadily increased. Drainage infrastructure in the UK was not designed for a changing climate, and many sewer systems in densely populated urban areas, are unable to cope. Sewage overflow and surface run off in urban areas can act as vectors for the dissemination of pathogens, known to cause disease among human populations. Most of the previous studies in this field have focused on using faecal indicators such as E.coli when assessing the public health risk of floodwater [1]. However, traditional indicators do not accurately reflect the true risk that urban flooding poses [2]. Little is understood in regards to the survivability and behaviour of pathogens in different urban settings, which are fundamental to determine potential risks to public health. Previous investigations in UK waterlogged soils have shown a clear response of microbial communities to water table variation, temperature, and nutrient availability in soil profiles [3]. This research aims to investigate, using advanced molecular methods, the dynamics of pathogens (i.e. movement through soil and survival rates), and microbial interactions at the soil/water interface- collecting information from field work studies and laboratory-controlled experiments. The outcomes from this research will inform future management strategies of flooded sites that will aid to protect public health

Quantifying uncertainty in simulation of sewer overflow volume

Environmental regulators frequently stipulate the modeling approaches required for water utilities managing sewer networks to demonstrate regulatory compliance. The performance of drainage systems with regard to combined sewer overflow (CSO) discharges is required to be assessed using urban drainage models to prove compliance before large investments can be authorized. However, as far as the authors are aware, the modeling approaches to demonstrate regulatory compliance currently provide no opportunity for considering model uncertainty. This paper therefore addresses a knowledge gap in the role of model uncertainty in environmental compliance studies by describing an objective uncertainty quantification process that enables the water utilities to evaluate and report the uncertainty in their modeling predictions and that is also transparent enough to satisfy regulators. The sewer network was modeled in InfoWorks CS software using a design storm defined by the regulator to test the performance of CSOs. Uncertainty in the model and input parameters was propagated using Monte Carlo simulations with Latin hypercube sampling, and the results were presented to show the trade-off between the infrastructure investment and the risk of spilling

Acceptability of Parental Financial Incentives and Quasi-Mandatory Interventions for Preschool Vaccinations: Triangulation of Findings from Three Linked Studies.

BACKGROUND: Childhood vaccinations are a core component of public health programmes globally. Recent measles outbreaks in the UK and USA have prompted debates about new ways to increase uptake of childhood vaccinations. Parental financial incentives and quasi-mandatory interventions (e.g. restricting entry to educational settings to fully vaccinated children) have been successfully used to increase uptake of childhood vaccinations in developing countries, but there is limited evidence of effectiveness in developed countries. Even if confirmed to be effective, widespread implementation of these interventions is dependent on acceptability to parents, professionals and other stakeholders. METHODS: We conducted a systematic review (n = 11 studies included), a qualitative study with parents (n = 91) and relevant professionals (n = 24), and an on-line survey with embedded discrete choice experiment with parents (n = 521) exploring acceptability of parental financial incentives and quasi-mandatory interventions for preschool vaccinations. Here we use Triangulation Protocol to synthesise findings from the three studies. RESULTS: There was a consistent recognition that incentives and quasi-mandatory interventions could be effective, particularly in more disadvantaged groups. Universal incentives were consistently preferred to targeted ones, but relative preferences for quasi-mandatory interventions and universal incentives varied between studies. The qualitative work revealed a consistent belief that financial incentives were not considered an appropriate motivation for vaccinating children. The costs of financial incentive interventions appeared particularly salient and there were consistent concerns in the qualitative work that incentives did not represent the best use of resources for promoting preschool vaccinations. Various suggestions for improving delivery of the current UK vaccination programme as an alternative to incentives and quasi-mandates were made. CONCLUSIONS: Parental financial incentives and quasi-mandatory interventions for increasing uptake of preschool vaccinations do not currently attract widespread enthusiastic support in the UK; but some potential benefits of these approaches are recognised.National Institute for Health Research (Grant ID: HTA 11/97/01)This is the final version of the article. It first appeared from PLOS via http://dx.doi.org/10.1371/journal.pone.015684

Evaluation of a coupled hydrodynamic-closed ecological cycle approach for modelling dissolved oxygen in surface waters

The description of intertwined ecological processes in surface waters requires a holistic approach that accounts for spatially distributed hydrological/water quality processes. This study describes a new approach to model dissolved oxygen (DO) based on linked hydrodynamic and closed nutrient cycle ecological models. Long term datasets from the River Dommel (Netherlands) are used to determine: 1) if this methodology is suitable for modelling DO concentrations, 2) the model sensitivity to various levels of nutrients input, and 3) the DO production and consumption processes and their response to nutrient input changes. Results show that seasonal dynamics of DO are well quantified at long timescales; the sensitivity of DO to different pollutant sources exhibits significant seasonal variation and the largest influences on DO are aeration and mineralization of organic material. The approach demonstrates an ability to consider the impacts of nutrient input and long term vegetation maintenance on ecological quality