Impact of vegetation in open channels on flow resistance and solute mixing.

This thesis has investigated the impacts of vegetation on flow resistance and mixing in open channel flow. Existing methods and models proposed by previous research which predict flow and mixing in vegetated channels have been presented and discussed. The most pressing issues have been identified as a lack in understanding of how vegetation affects solute mixing, and a lack of verification of existing flow resistance models in situations involving real rather than simulated vegetation. To address these issues, a detailed laboratory study has been undertaken. This involved growing real vegetation in the laboratory environment and conducting tests whilst the vegetation grew in size, density and stiffness. Two vegetation types (Carex and Phragmites Australis) were used to provide an indication of how different plant species affect flow and mixing. Experiments involved the collection of flow resistance, velocity, turbulence and transverse and longitudinal mixing data at different stages of plant growth and whilst the vegetation was in both emergent and submerged states. This involved the use of an acoustic Doppler velocity probe to measure velocity and turbulence. Measurements of mixing were made using CYCLOPES-7 fluorometers with fluorescent tracer used as solute. The presence of vegetation increased the channels flow resistance. As the vegetation grew the resistance increased. In emergent conditions direct measurements of velocity and Reynolds stress were retarded compared to non vegetated experiments and reduced longitudinal mixing was observed. In submerged conditions more complex profiles of velocity and Reynolds stress were measured and longitudinal mixing was dependant on the canopies submergence ratio and the rate of vertical mass transport between the flow above and within the canopy. Results were compared with predictions made by existing vegetated flow models. New models and methodologies for predicting flow and mixing in vegetated canopies have been presented and tested against the data with good results

Cost effective measuring technique to simultaneously quantify 2D velocity fields and depth-averaged solute concentrations in shallow water flows

This paper presents a cost-effective methodology to simultaneously measure mixing processes and surface velocity fields in shallow flows using low cost cameras and lighting. Velocity fields and depth averaged concentration of a soluble fluorescent tracer are obtained using the new techniques and the results verified against traditional point probe measurements in a laboratory flume. An example of simultaneous velocity/concentration measurement is presented for an instantaneous release of tracer into flow around an obstruction. The method will help to improve the understanding of mixing processes in shallow open channel flows. It is anticipated that the technique will be useful in physical modelling studies where the mixing and hydraulic length scales under investigation are in the order of 1-10 m, for example in compound channels and partially vegetated streams

The Generationing of Power: A Comparison of Child-Parent and Sibling Relations in Scotland

The paper concentrates on an exploration of power relations within families. The paper discusses parental power in relation to legitimacy, household resources and children’s anticipated reactions of adult discipline. The nature of sibling power is highlighted before exploring the reciprocal expectations of sibling and child-parent interactions. The paper ends by suggesting that the generationing of power relations can lead to differing degrees of backstage and frontstage performances within the home

The association between social capital and mental health and behavioural problems in children and adolescents: an integrative systematic review

Background Mental health is an important component of overall health and wellbeing and crucial for a happy and meaningful life. The prevalence of mental health problems amongst children and adolescent is high; with estimates suggesting 10-20% suffer from mental health problems at any given time. These mental health problems include internalising (e.g. depression and social anxiety) and externalising behavioural problems (e.g. aggression and anti-social behaviour). Although social capital has been shown to be associated with mental health/behavioural problems in young people, attempts to consolidate the evidence in the form of a review have been limited. This integrative systematic review identified and synthesised international research findings on the role and impact of family and community social capital on mental health/behavioural problems in children and adolescents to provide a consolidated evidence base to inform future research and policy development. Methods Nine electronic databases were searched for relevant studies and this was followed by hand searching. Identified literature was screened using review-specific inclusion/exclusion criteria, the data were extracted from the included studies and study quality was assessed. Heterogeneity in study design and outcomes precluded meta-analysis/meta-synthesis, the results are therefore presented in narrative form. Results After screening, 55 studies were retained. The majority were cross-sectional surveys and were conducted in North America (n = 33); seven were conducted in the UK. Samples ranged in size from 29 to 98,340. The synthesised results demonstrate that family and community social capital are associated with mental health/behavioural problems in children and adolescents. Positive parent–child relations, extended family support, social support networks, religiosity, neighbourhood and school quality appear to be particularly important. Conclusions To date, this is the most comprehensive review of the evidence on the relationships that exist between social capital and mental health/behavioural problems in children and adolescents. It suggests that social capital generated and mobilised at the family and community level can influence mental health/problem behaviour outcomes in young people. In addition, it highlights key gaps in knowledge where future research could further illuminate the mechanisms through which social capital works to influence health and wellbeing and thus inform policy development

Designing an environmental flow framework for impounded river systems through modelling of invertebrate habitat quality

Many rivers have undergone flow modification by impoundments to provide services such as water supply and hydropower. There is an established consensus that typical modified flow regimes do not sufficiently cater to the needs of downstream ecosystems, and more must be done to understand and mitigate their associated impacts. This study presents a novel, transferable framework by which a small-scale impoundment in North West England is assessed through the use of linked hydro-ecological modelling in SRH-2D and CASiMiR, utilising flow velocity measurements and macroinvertebrate sampling data. Model predictions of habitat quality were supplemented by established ecological principles such as the importance of flow heterogeneity. Results are used to design environmental flow regimes, with the aim of improving ecological metrics whilst considering conflicting water demands. Based on an analysis of historical flow records, the implementation of designer flows over a 12 month period demonstrated increased peak species habitat qualities of 23–26%, characteristics such as flow heterogeneity were more naturalised, and 22% less water was released from the impoundment. Should outcomes be validated by in-stream flow experiment, there is great potential for further development and application of this method, including regional transferability for the rapid designation of environmental flows across a number of sites of similar magnitude and geography

Optimal Positioning of RTC Actuators and SuDS for Sewer Overflow Mitigation in Urban Drainage Systems

Real-time control (RTC) and sustainable drainage systems (SuDS) can be implemented simultaneously to enhance the performance of existing urban drainage systems (UDS). However, significant challenges arise when choosing the optimal locations due to hydraulic interactions between the different interventions and the high number of possible configurations. This paper presents a novel optimization–simulation framework to optimize the spatial allocation of flow control devices (FCDs) combined with SuDS for combined sewer overflow (CSO) spill mitigation within UDS. Optimal intervention schemes were identified by a genetic algorithm (GA), combining different numbers of FCDs installed in existing manholes with simplified SuDS implemented in different portions of the catchment. The methodology was tested on two case-study catchments with different characteristics to mitigate CSO spills during synthetic storm events. FCD-SuDS configurations were then validated during continuous rainfall series, resulting in CSO spill volumes reduction ranging between 11% and 45% compared to the baseline networks. The results demonstrate how the GA-based method can efficiently identify optimal placement schemes within UDS characterized by different distributions of in-pipe storage potential as well as hydrological responses to rainfall-runoff events, enhancing the combined benefits of the two decentralized solutions for mitigating CSO spills