Showing papers by "Mott MacDonald published in 2012"

The Integration of Agent-Based Modelling and Geographical Information for Geospatial Simulation

Abstract: Within this chapter we focus on the integration of Geographical Information System (GIS) and Agent-based modelling (ABM) and review a selection of toolkits which allow for such integration. Moreover, we identify current capabilities of modelling within a GIS and methods of coupling and integrating GIS with agent-based models. We then introduce suggested guidelines for developing geospatial simulations with ABM toolkits and offer practical guidelines for choosing a simulation/modelling system before providing a review of a number of simulation/modelling systems that allow for the creation of geospatial agent based models along with the identification of a number references for further information.

Suppressing antagonistic bioengineering feedbacks doubles restoration success

Abstract: In a seagrass restoration project, we explored the potential for enhancing the restoration process by excluding antagonistic engineering interactions (i.e., biomechanical warfare) between two ecosystem engineers: the bioturbating lugworm Arenicola marina and the sediment-stabilizing seagrass Zostera noltii Hornem. Applying a shell layer underneath half of our seagrass transplants successfully reduced adult lugworm density by over 80% and reduced lugworm-induced microtopography (a proxy for lugworm disturbance) at the wave-sheltered site. At the wave-exposed site adult lugworm densities and microtopography were already lower than at the sheltered site but were further reduced in the shell-treated units. Excluding lugworms and their bioengineering effects corresponded well with a strongly enhanced seagrass growth at the wave-sheltered site, which was absent at the exposed site. Enhanced seagrass growth in the present study was fully assigned to the removal of lugworms' negative engineering effects and not to any (indirect) evolving effects such as an altered biogeochemistry or sediment-stabilizing effects by the shell layer. The context-dependency implies that seagrass establishment at the exposed site is not constrained by negative ecosystem-engineering interactions only, but also by overriding physical stresses causing poor growth conditions. Present findings underline that, in addition to recent emphasis on considering positive (facilitating) interactions in ecological theory and practice, it is equally important to consider negative engineering interactions between ecosystem-engineering species. Removal of such negative interactions between ecosystem-engineering species can give a head start to the target species at the initial establishment phase, when positive engineering feedbacks by the target species on itself are still lacking. Though our study was carried out in a marine environment with variable levels of wave disturbance, similar principles may be expected to apply to other ecosystems that are inhabited by ecosystem engineers.

Water resources assessment in the Minqin Basin: an arid inland river basin under intensive irrigation in northwest China

Abstract: The Minqin Basin is at the lower reach of the Shiyang River of Gansu province in northwest China. Dramatic decline in groundwater level has resulted from over-abstraction of groundwater since the late 1950s to satisfy increasing irrigation and other demands. Severe water shortage led to environmental degradation. To better understand the spatial-temporal variation of groundwater levels and to evaluate the groundwater resources in the region, a three-dimensional regional groundwater flow model was built and calibrated under transient condition. The MODFLOW program was used and the research area was discretized as a square network with cell size of 400 9 400 m. The model showed that the aquifer was under destructive stress, with a groundwater resource def- icit of 260 million cubic meters per year (Mm 3 /year) on average. Since the inflow of surface water from the upstream basin has declined to about 100-150 Mm 3 /year in recent decades, the irrigation return flow had become the main recharge and accounted for 60.6% of total recharge; meanwhile, abstraction by pumping wells took 99.2% from the total groundwater discharge.

Modelling the hydrogeology and managed aquifer system of the Chalk across southern England

Abstract: Abstract Six regional recharge and groundwater models have been recently developed of the Chalk and Upper Greensand from Dorset to Kent. Updated Chalk stratigraphy and mapping have improved understanding of geological structure and the development of preferential groundwater flow pathways along hardground horizons. Where shallow dipping folds bring these into the zone of active groundwater flow, extensive ‘underdrainage’ may result in marked differences between surface and groundwater catchments. Hardgrounds and marls are also associated with spring discharges, as are some faults and the clay formations that underlie or confine the aquifer system. Higher specific yield within the Upper Greensand helps support summer baseflow, as do local groundwater discharges from augmentation schemes, watercress and fish farm operations. The aquifer system has been successfully modelled using the ‘variable hydraulic conductivity with depth’ version of MODFLOW. Depths of secondary permeability development have been distributed according to ground and groundwater level data. Interfluve–valley contrasts overlie a base hydraulic conductivity set according to the formation saturated at the water table and enhanced by active hardgrounds. Local parameter overrides may also be needed. The Wessex Basin conceptual and numerical model is described before summarizing similarities and contrasts from the other five regional model areas.

Start, development and status of the regulator-led national groundwater resources modelling programme in England and Wales

Abstract: Abstract Over the last 10 years there has been a unique regulator-led programme involving extensive development of regional groundwater models across England and Wales for water resources purposes by the Environment Agency for England and Wales. Eight regionally managed programmes are underpinned by a framework, which has allowed a coordinated national approach. The main uses of the models are for catchment abstraction management and licensing. Models have also assisted in monitoring network design, investigating groundwater quality and implementing groundwater source protection zones. A five-yearly review of the programmes recognized the importance of benefit realization and stakeholder involvement as well as technical good practice. The programme already delivered provides a solid foundation for supporting the management decisions required in areas such as climate change mitigation and integrated catchment management using appropriate tools at a time of rapid organization change and financial uncertainty.

Carbon Footprint Incorporation into Least-cost Planning of Eco-city Schemes: Practices in Coastal China

Abstract: Eco-city planning has been a prevailing concern throughout China and beyond over the past few decades. Least-cost planning is a life-cycle costing approach for alternative analysis and decision-making, determining the preferred option that provides the optimal mix of financial, social and environmental outcomes for stakeholders throughout the project lifespan. A more sustainable approach is to incorporate the low carbon context into this economic analysis. Case studies, Tianjin Eco-city and Ningbo-Cixi Wetland Centre, granted by GEF, are presented and reviewed on how to foster key coastal areas of China into eco-cities by means of carbon footprint and costing. It is demonstrated that consideration should include carbon impact, carbon costs and accounting processes in the planning and management of the relevant plots, with achievement of key performance indicators relating to greenhouse gasses. Tertiary wastewater treatment, the selection of low carbon emission technology, and the utilization of constructed wetland configurations, green buildings and facilities are particularly demonstrated and modelled, employing energy software and economics tools repectively.

Groundwater resource modelling for public water supply management in London

Abstract: In London, groundwater abstractions for public supply are predominantly from the Chalk aquifer. However, water resource pressures put existing abstractions at risk and often require complex analysis to support new source development. Thames Water develops and uses regional groundwater models for such analysis to support communication with stakeholders such as the Environment Agency, the environmental regulator of England and Wales. Using two case studies, the importance of regional models as Thames Water assets is demonstrated. While Thames Water has developed regional models as a context for sub-catchment scale analysis of groundwater source development, they are subsequently used to address other issues. As a result, the models are updated regularly, enhancing both conceptual understanding and calibration. These models cost less than 1% of the capital cost of new water source schemes. However, as they are enhanced and applied more widely, the models accrue further value as active decision support tools. Regional model usage to investigate a range of local systems and interactions is of particular value to Thames Water. In this regard, it is important to appreciate and promote the clarity and consistency generated when stakeholder-specific issues can be analysed within an agreed regional model framework.

Recharge estimation methodologies employed by the Environment Agency of England and Wales for the purposes of regional groundwater resource modelling

Abstract: Abstract Recharge calculations based on daily soil moisture balance models define the resource available for most regional-scale groundwater models used by the environmental regulator in England and Wales. A switch in recent years from the Penman–Grindley methodology to the Food and Agricultural Organization approach has improved the representation of soil properties in these calculations. A new Meteorological Office algorithm for calculating potential evapotranspiration inputs has also been adopted and rain-gauge data processing on individual models are currently being streamlined towards the use of nationally derived grids. A range of infiltration, bypass and runoff–recharge mechanisms have been conceptualized and modelled incorporating simple representation of unsaturated zone storage and flow processes. This paper reviews the recent changes adopted and considers future challenges.

Managed Motorways: Modeling and Monitoring Their Effectiveness

Abstract: Managed motorways (formerly known as active traffic management) aim to address traffic congestion and improve journey time reliability with a set of advanced applications of intelligent transport systems to maximize available road capacity. An important feature of managed motorways is the use of hard shoulder running together with variable mandatory speed limits during periods of congestion. Managed motorways were first trialed in the Netherlands and have been in operation in the United Kingdom since 2006. This paper presents the monitoring results of the introduction of managed motorways around Birmingham in the United Kingdom and also describes modeling methods that were used to generalize the findings. Managed motorways around Birmingham have been so effective that they are to be introduced by the UK Highways Agency across the wider network. This paper summarizes the findings of 5 years of monitoring and modeling and refers to the wider set of papers and reports in the public domain for deeper analysis. The paper describes the rigor in monitoring before and after data and in the modeling support for the assessment of outcomes of this transportation investment decision; these outcomes include a reference to the relationship with the economic development in the area. Discussion includes results from a before and after data analysis exercise, the contribution by microsimulation modeling, and findings from an extensive consultation exercise with users of the scheme. The wider economic impacts of investment in managed motorways are examined. The intention is to produce guidance for those transportation organizations that are considering the implementation of managed motorways elsewhere in the world, in particular in the United States.

How to get your model results used: a guide to stakeholder engagement

Abstract: The usage of modelling results by their intended audience is an important aspect of undertaking any project. However, providing the appropriate results in the correct way to key stakeholders is not a straightforward task. Fortunately, there is a growing body of work about approaching the engagement of stakeholders in a way to maximize the impact of modelling results. Using the lessons learnt from a number of recent workshops, including those conducted for the benefits realization process undertaken for the Environment Agency of England and Wales, suggestions for best practice are presented and their relative merits discussed. Best practice for getting groundwater modelling results used by their intended audience is proposed.

Optimum use of material: selection of limits for suitable earthworks fill:Irish experience

Abstract: Most Irish earthworks fills consist of glacially derived soils with some excavated rock. Excavated rock and granular glacial soils will nearly always provide acceptable fill. Cohesive glacial soils are generally well-graded tills, characterized by low plasticity and relatively high undrained strength. These cohesive tills provide acceptable fills providing they can be placed and compacted to provide sufficient strength and stiffness, and achieve low air voids. In standard earthworks specifications, acceptability limits for cohesive fills may be specified by moisture content, moisture condition value or undrained shear strength. The lower limit of strength or moisture content adopted ensures acceptable trafficability, compressibility and stability. Laboratory relationship testing is carried out to establish the relationship between the various test properties. Experience has shown that simple measurements and descriptions of strength derived from data collected routinely during ground investigations are adequate for estimation at tender. For construction control, moisture condition value testing has been widely adopted, is suitable for the range of soils encountered and provides quick results allowing timely decision-making. Irish tills are moisture susceptible and on-site results allow marginal materials to be processed on site for re-use, providing care is taken to work only in dry weather and protect placed fill.

Geotechnical asset management for the UK Highways Agency

Abstract: This paper outlines the Geotechnical Asset Management Strategy of the Highways Agency (HA). The strategy operates in a series of key stages, from setting standards and advice, through data collection and analysis through to the ultimate aim of providing and maintaining an asset that meets the service level that it is required to attain. These key stages are outlined, and illustrated with examples where appropriate. The HA, and its managing agents, have progressed a significant way along the ‘roadmap’, but further work is still ongoing. A key tool for the delivery of the HA Geotechnical Asset Management Strategy is the Geotechnical Data Management System (HA GDMS). This is discussed throughout the paper, and examples of the functionality of the system are given.

Evaluation of the Birmingham Box Managed Motorways Phases 1 and 2

Abstract: The Birmingham Box Managed Motorway (BBMM) Phases 1 and 2 schemes were introduced on sections of the M6, M42 and M40 motorways near Birmingham, UK. The primary objective of the schemes was to improve traffic conditions and journey time reliability during periods of congestion through the use of intelligent transport systems and by making best use of existing road space. BBMM Phase 2 was also the first site to introduce `through junction running' on a full-time basis in the UK. Traffic data analysis was undertaken to understand the impact of managed motorway operations on this section of road. The results demonstrate that the introduction of the schemes has improved traffic conditions at these sites with additional benefits being observed on the M42 Managed Motorway (M42-MM) section. (6 pages)

Voltage unbalance protection VT and relay errors effect on unbalanced voltage detection; Considerations for system relaying, stability and developments

Abstract: In a power system network, an unbalanced voltage condition can occur due to various reasons. Excessive voltage unbalance has become an issue of concern in power quality at network level, leading to numerous problems. This calls for a stringent management of unbalanced. There are several codes of practice to advise and to enforce network operating conditions to keep system unbalance within specific limits. Analysis of system unbalance voltage and power system control is carried out through Voltage Transformers and protective relays. The accuracy of Voltage Transformers from primary to secondary varies according to the type (Class of VT). Also, the accuracy of Relays is of the concern to the same extent. This poses a limitation on detection of actual system unbalance. This study gives an overview of fundamentals of sequence components, unbalanced voltage definitions and use of different types of VTs and relays to analyse unbalanced voltage. This paper considers detection of low level voltage unbalance equivalent to maximum limits allowed in national grid codes in order to initiate system to generate tripping/alarm. This article endeavours to summarise deviational effect of accuracy levels of VT and relays. The study provides a reference of selection of VTs and Relays to detect known % unbalance in the system. Coverage has been extended to discuss mitigation techniques of voltage unbalance and deviational error minimisation. The emphasis is to initiate a thought process for requirement of improved methodologies to eliminate errors in analysing. Therefore this study aims in building a better power system.

The identification and management of cuttings at risk from deep-seated, delayed failure on the Highways Agency network

Abstract: The UK trunk road network includes a considerable number of cuttings constructed through high plasticity, overconsolidated clays. These materials are prone to the process of delayed, deep-seated failure whereby instability can occur some considerable time after construction. The timescale between excavation and failure can be anywhere between 20 and 120 years. Many of the recorded deep-seated failures in the literature are from railway cuttings in the UK which are generally much older than cuttings on major highways. The bulk of trunk road construction in the UK occurred during the 1960s and 1970s and many cuttings are at, or approaching, an age when delayed, deep-seated failures might be expected to occur. The Highways Agency (HA) has been aware of this issue and has sought to understand the causes and associated risks of these types of failure. The first phase of a study (concluded in 2007) provided a framework for assessing the likelihood of failure. The selection criteria were based on a combination of cutting height and slope angle. Mott MacDonald was commissioned to undertake the second phase of the study to focus on the application of the Phase 1 recommendations to the HA asset base. This paper describes the work undertaken during this study and conclusions reached.

Nuclear power for the vision 2030 of Abu Dhabi and improvement of air quality

Abstract: There has a been great deal of discussion ongoing in the United Arab Emirates to look for sustainable forms of energy. As one of the leading countries in production of greenhouse gas it has become essential for the nation to look for alternative sources of energy. Abu Dhabi is establishing its first nuclear power station in the near future so it is also important to look at the adverse effect of this energy source and try to control the potential hazard related to it. Air quality issue improvement and nuclear waste disposal are two main issues related to nuclear power station. This paper will focus on the role of nuclear power to attain the 2030 vision of Abu Dhabi and how nuclear power can also help to improve the air quality of this region.

An Urban Tunnelling Challenge – A Case Study for a Tunnel under an Ancient Tree Wall in Hong Kong

Abstract: Achieving the balance of civilisation versus heritage preservation is becoming a significant consideration for civil engineering and tunnelling projects worldwide. This is especially the case in the highly urbanised city of Hong Kong, whereby much of the new infrastructure conflicts with and impinges upon the concentrated areas of historical and heritage features that are treasured by the community. This paper considers one recent case study, relating to the upgrading railway network projects of West Island Line (WIL) in Hong Kong, which is at a particular location facing the challenge of constructing a 12 m span railway tunnel underneath a ‘valuable ancient tree wall’ with only 10 m ground cover. Such challenge is a serious issue for tunnel works in Hong Kong since no disturbance to such community assets can be allowed. Hence, this section of the project involves tunnelling through shallow mixed ground conditions whilst simultaneously preserving the tree wall. This made the engineering design one of the ...

Investigation of a cascaded tripping incident

Abstract: This paper investigates an incident that occurred in a grid connected aluminum smelting plant that resulted in cascaded tripping of power plant parts and eventual system instability. The incident was initiated by tripping of an interconnector due to the operation of its directional over-current relay. The results of the power system simulation studies are described to explain the transient performance of the system during the incident. Having identified the main area of the electrical system weakness, an under frequency load shedding scheme is designed and implemented in practice to maintain the system stability during the most severe loss of generation scenarios. The paper demonstrates how using a detailed dynamic simulation of the electrical network can be used to assist with post event analysis, and provides additional insight into the dynamic performance of the system which cannot be obtained using only SCADA or PMS data. The good correlation between measured and simulated data confirms the veracity of the model and gives confidence in the proposed under frequency load shedding scheme.

New Criteria for Assessing the Local Wind Environment at the Pedestrian Level and the Applications

Abstract: The wind environment is a stochastic phenomenon. To deal with this stochastic feature, this chapter introduces the use of exceedance probability analysis to evaluate the properties of the wind. Two representative indices were adopted: the local purging flow rate (LPFR) and the space-averaged kinetic energy of the wind (KE). The former was used to express the ability of airflow to exhaust contaminants generated within a given space, and the latter was used to represent the ability of airflow to cool the human body. The local air change rate (LACR), defined as the local purging flow rate per volume of void space, was used as the ventilation index for application. The exceedance probability (EP) was calculated based on the wind speed distributions described by the Weibull function for 16 azimuths to indicate the exceedance probability of a given air change rate. The exceedance probability of the kinetic energy of the wind in the void space was also evaluated in the same manner as the local air change rate. Acceptable values of the exceedance probability for both the local air change rate and the space-averaged kinetic energy of the wind in the void space were suggested based on acceptable indoor environmental indices.

Geotechnical risk and performance: with a focus on earthworks compaction and data management

Abstract: This paper discusses the various influences controlling risk and performance from new build to the in-service aspects of the transport infrastructure geotechnical asset of which earthworks are the major part. First it focuses on the risks associated with earthworks during construction. Compaction specifications, their origins and past supporting research results are described as are the advantages and disadvantages of the end-product. The method specification gives an insight into the development of earthworks design, construction and contracts. Recommendations are given based on modern practice and current contractual arrangements. Monitoring performance is critical to the management of geotechnical assets and the establishment of IT based methods in the UK is discussed to complete a ‘cradle to grave’ review of risk and performance aspects of earthworks.