Scott Arthur

SUDS, LID, BMPs, WSUD and more - The evolution and application of terminology surrounding urban drainage

The management of urban stormwater has become increasingly complex over recent decades. Consequently, terminology describing the principles and practices of urban drainage has become increasingly diverse, increasing the potential for confusion and miscommunication. This paper documents the history, scope, application and underlying principles of terms used in urban drainage and provides recommendations for clear communication of these principles. Terminology evolves locally and thus has an important role in establishing awareness and credibility of new approaches and contains nuanced understandings of the principles that are applied locally to address specific problems. Despite the understandable desire to have a ‘uniform set of terminology’, such a concept is flawed, ignoring the fact that terms reflect locally shared understanding. The local development of terminology thus has an important role in advancing the profession, but authors should facilitate communication between disciplines and between regions of the world, by being explicit and accurate in their application.

The influence of near bed solids transport on first foul flush in combined sewers

The problems associated with deposited sediments in sewers, and their transport through sewer systems have been the subject of detailed fieldwork programmes in the UK, and elsewhere in Europe. Existing laboratory, and some field based research exercises have focused on the relatively small, discrete particles. It is clear, however, that combined sewer systems have inputs which comprise of a significant proportion of large organic solids (faecal and food wastes), as well as the finer range of particle sizes. The increased concern regarding CSO spills into the environment has fuelled the recent development of sewer flow quality models, such as HYDROWORKS QM and MOUSETRAP, some of which make no attempt to represent the transport of these larger organic particles. Herein, the results of a collaborative research programme undertaken between three UK universities and a water authority are discussed. Transport at the bed in sewers, as “near bed solids”, is defined. Based on a comprehensive data collection program undertaken in the Dundee combined sewerage system, a method is presented which may be used to estimate the rate of sediment transport near the bed in sewers. The influence that solids in transport near the bed have on first foul flush in combined sewers is discussed. A methodology is proposed which may be used to estimate the extent to which sediment in transport near the bed in sewers contributes to first foul flush phenomena, by describing the movement of a storm wave along a conceptual sewer length.

Siphonic roof drainage system analysis utilising unsteady flow theory

Abstract Over the past three years a UK EPSRC research programme has been underway at Heriot-Watt University investigating siphonic roof rainwater systems. This text aims to report the principle findings of the project to date. A brief description of experimental and numerical aims is given. The priming procedure which occurs in an idealised system is documented. The test procedures employed are described, and experimental results are illustrated. The framework employed to numerically model the ambient hydraulics is described in some detailed. Conclusions are drawn regarding the operational characteristics of siphonic roof rainwater systems as a whole.

The performance characteristics of multi-outlet siphonic roof drainage systems

Siphonic roof drainage systems have been in existence for approximately 30 years, and are becoming an increasingly common element of urban drainage infrastructure. In that time, the construction sectorin most developed countries have been gradually persuaded of the benefits that these systems offer when compared to conventional roof drainage technologies. The work reported herein details anongoing UK government-funded research programme to investigate the performance characteristics of multi-outlet siphonic roof drainage systems. The experimental aims, apparatus and procedures are described, and results are illustrated. In addition, ‘real’ data obtained from three installed siphonic roof drainage systems are discussed. Conclusions are drawn regarding the performance characteristics of multi-outlet systems, and plans for future work are outlined.

Siphonic roof drainage: Current understanding

Abstract Over the past five years there has been an ever increasing amount of independent research directed at understanding how siphonic roof drainage systems perform hydraulically. Since 1995, there has been a substantial amount of time and money invested in researching these systems by both government and industry. This increased amount of research activity means that, increasingly, publications are entering the public domain – the main source of this work being UK-based. This text aims to collate this work, and give an overview of what the current level of understanding is. Furthermore, it will analyse what this research means for existing systems, and recommend areas for future research in this field.

Assessment of heavy metals emission from traffic on road surfaces

This study aims to analyse RDS heavy metal concentrations on road deposited sediment (RDS) using Riccarton Campus of Heriot-Watt University, Edinburgh, Scotland as a study site. RDS samples were collected at two transverse positions from different sites over a 4 month period in order to describe the influence of traffic on heavy metal emissions. The heavy metal concentrations of the RDS were determined by strong nitric acid digestion and atomic absorption spectrometry. The mean concentrations for Zn, Cu, Cd, Cr, Ni, Pb and Fe were found to be 213, 57, 1, 16, 15, 118, and 13497 mg kg-1 from samples near to the curb and 211, 79, 2, 15, 9, 35, and 14276 mg kg−1 from samples 1 m from the curb respectively. Furthermore for both positions the highest concentrations for all metals were associated with the finer fraction (<63 µm) and stronger correlations between the metals were found further from the curb than near the curb, indicating that metals accumulating on the road surface further from the curb may likely be from the same source (traffic), while the sources of metals near the curb are more diverse.

Near bed solids transport rate prediction in a combined sewer network

The physical and biochemical nature of the material transported near the bed (‘bed-load’) in combined sewers is established. The merits of the recent evolution of the terminology used in this field are discussed. The physical characteristics of material found in transport at three separate combined sewer field sites are described. The importance of this mode of transport, in terms of the mass transported and pollutant potential, is demonstrated based on data collected from Dundee combined sewerage system sites. The development of a novel near bed solids transport prediction equation is described. Comparisons are made between measured near bed solids transport rates obtained in the field, at sites with and without deposited beds, with predictions obtained using the new methodology. The need for future research in this subject area is emphasised.

Public attitudes towards flooding and property-level flood protection measures

The number of residential properties at risk from flooding is predicted to rise in the future, and it is clear that large-scale flood defence schemes are not always feasible. There is thus an increasing onus on the public to protect their own properties. This paper reports the results of a stakeholder consultation investigating public attitudes towards flooding and property-level flood protection (PLFP) in general, and peoples’ “willingness to pay” for PFLP specifically. The findings show that flooded households have suffered significant financial and social impacts. Despite some continued uncertainty surrounding flood risk responsibility, the majority of the public surveyed were willing to pay for PLFP, with a mean contribution of approximately £800. Whilst this paper broadly confirms some of the findings of earlier studies, it also indicates that public education and promotion campaigns have been effective in raising awareness and uptake of PLFP and that people are willing to pay more to protect their properties. The findings also support the notion that an increased awareness of PFLP, and an increased willingness to pay for PLFP, is linked to the scale of flooding and impacts, rather than just the frequency, as well as financial subsidies. The results of the study are particularly relevant to institutional stakeholders, as they can help guide the development of strategies to increase the uptake of such measures. Whilst the project focuses on the situation in Scotland, the findings will have resonance in similar countries throughout Europe and beyond.

Numerical modelling of the priming of a siphonic rainwater drainage system

The operation of siphonic rainwater systems, and in particular their priming action, is described. Current industry recognised design procedures are discussed. The initial priming of a test facility developed to replicate current design practice is described in detail, and related to the expected performance of systems installed in the field. The impartance, hydraulically, of several specific elements of the system operation are emphasised in terms of the priming action. Additionally, problems encountered at start-up, due to air in both the system and the inflow, are highlighted. A numerical model is discussed that represents system priming, and conclusions are drawn regarding the data presented here and how they relate to the siphonic roof drainage industry as a whole.

Recent and future advances in roof drainage design and performance

The past 10 years have witnessed significant changes in the way roof drainage systems are understood and designed. In particular, there has been a stepchange in the confidence with which siphonic roof drainage systems may be specified and expected to perform. These changes have occurred whilst urban drainage design in general has been revolutionized by wider acceptance of Sustainable Urban Drainage Systems and greater public concern regarding pluvial flooding within the context of climate change. This text considers, in detail, both how roof drainage systems are designed and how they should be expected to perform. Particular attention is drawn to weaknesses in accepted design methods. Consideration is also given to ‘innovative’ roof drainage related approaches such as green roofs and rainwater harvesting. Practical application: Over the past few years there have been many changes in how roof drainage systems are specified and designed. On large buildings, technologies such as ‘siphonic roof drainage’ are now commonplace and there is an ever increasing demand for ‘green roofs’ to be specified due to their potential to ‘green’ developments. Based on ongoing research, this paper details how these different types of roof drainage solutions can be efficiently designed and what levels of performance can be expected.