Enda O'Connell

Newcastle University, School of Civil Engineering and Geosciences, Faculty Member

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Papers by Enda O'Connell

Small sample estimation of ρ1

Water Resources Research, 1972

Hydrologists frequently need to estimate lag 1 correlation Pl from rather short observed records ... more Hydrologists frequently need to estimate lag 1 correlation Pl from rather short observed records of length n. The most commonly used algorithms for estimating Pl can give seriously biased estimates if n is small and ]p•] is large. Small sample bias corrections based on the assumption of a lag 1 Markov generating process are available for •1, but the corrected estimates tend to have larger variance than the uncorrected estimates do.

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Annotated Bibliography from A restatement of the natural science evidence concerning catchment-based ‘natural’ flood management in the UK

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Towards Adaptation of Water Resource Systems to Climatic and Socio-Economic Change

Water Resources Management, 2017

Climate change is viewed as the major threat to the security of water supplies in most parts of t... more Climate change is viewed as the major threat to the security of water supplies in most parts of the world in the coming decades, and the water resources literature continues to be dominated by impact and risk assessments based on the latest climate projections from General Circulation Models (GCMs). However, the evidence for anthropogenic changes in precipitation and streamflow records continues to be elusive which, together with the known high uncertainty in GCM ensemble projections, has led to the development of risk assessment methods which are not driven exclusively by GCMs. It is argued that a baseline risk assessment should retain the assumption of climatic stationarity, and be based on the modelling of observed interannual variability as a dominant process in determining water resource system reliability, augmented where justifiable by reliable information from GCMs. However, irrespective of what the climate does in the future, globalization and socioeconomic changes are the major drivers for increases in water demand and threats to water security, as exemplified by the burgeoning economies of the BRIC and MINT countries, and the large population increases and economic growth seen in many developing countries. It is suggested that more attention needs to be paid to adaptation to socioeconomic change which is arguably more predictable than climatic change, based on what is already known about population and economic growth, lifestyle changes and human choices. More focus is needed on economic analyses that can inform the major investments in water use efficiency measures which can deliver the water savings needed to avert widespread water scarcity. The effectiveness of water use efficiency measures is largely determined by (a) the potential of modern information technology to achieve more efficient water resources management and water use and (b) human responses and choices in the uptake of measures. To assess the potential efficiency gains, it is argued that water resource systems modelling needs to evolve to incorporate the human dimension more explicitly, through Coupled Human and Natural Systems (CHANS) modelling. A CHANS modelling framework is outlined which incorporates agent-based

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From Open Channel Hydraulics to Earth Systems Engineering

Over the past decade, the evidence for the link between greenhouse gas emissions and global clima... more Over the past decade, the evidence for the link between greenhouse gas emissions and global climate change has become compelling. Accordingly, there has been a distinct shift in emphasis from providing scientific proof of anthropogenically-driven global climate change to consideration of what mitigation and adaptation strategies should be pursued. Water resources are already under heavy pressure in many parts of the world, and these pressures will increase due to accelerating population growth and urbanization. Climate change is expected to lead to an intensification of the hydrological cycle, with floods and droughts becoming more frequent and intensive. Predictive tools are needed to assess the impacts of climate change on water resources availability, flood risk, and water quality and erosion/sediment transport regimes, and to determine the most appropriate interventions to mitigate and adapt to the expected impacts.

Risks and Extremes

Rodda/Progress in Modern Hydrology: Past, Present and Future, 2015

This chapter describes the research activity on risks and extremes at Wallingford. With the agree... more This chapter describes the research activity on risks and extremes at Wallingford. With the agreement of the Steering Committee, the Flood Studies Report (FSR) (NERC, 1975) was published in 1975 in five volumes, containing the hydrological recommendations, the meteorological and flood routing studies and the hydrological data and maps. By the mid 1990s, the principal methods of rainfall and flood frequency used in the UK had been based on the FSR for 20 years, and it was recognised that there were significantly more rainfall and flood data available that should be incorporated into estimation methods. In the years following the publication of the Flood Estimation Handbook (FEH), a number of new sources of river flow and catchment data became available and substantial improvements were made to some key elements of the flood estimation procedures. Applied research into flood estimation continues to be an important topic.

Science and Water Policy Interface

Concepts, Methodologies, Tools, and Applications

Despite many advances in the field of hydroinformatics, the policy and decision-making world is u... more Despite many advances in the field of hydroinformatics, the policy and decision-making world is unable to use these highly technical decision support systems (DSSs) because there has been an undue emphasis on the technological aspects. The historical analysis of hydroinformatics concepts and modelling shows that the technical aspects have been incorporated far better than the social aspects. Hence, there have been calls for the development of ‘socio-technical’ DSSs. However, far greater effort is required to incorporate social and political sciences into the domain of DSSs. The goal of this chapter is to elaborate on the illusive interface between science and water policy within the context of DSSs. It is an attempt to address one main question: how to link or find an interface between policy (institutional matters) and science (technical and natural environment aspects). To achieve this goal, a new paradigm for the DSS modelling approach has been envisaged based on combining multip...

Gupta Receives 2008 Robert E. Horton Medal

Eos, Transactions American Geophysical Union, 2009

ABSTRACT Vijay K. Gupta was awarded the 2008 Robert E. Horton Medal at the AGU Fall Meeting Honor... more

An analysis of the dynamic component of the geomorphologic instantaneous unit hydrograph

Journal of Hydrology, 1996

The determination of characteristic flow velocity is a hydrodynamic problem needs to be solved in... more The determination of characteristic flow velocity is a hydrodynamic problem needs to be solved in the application of geomorphologic instantaneous unit hydrograph (GIUH) for runoff simulation in areas with no or limited data. In this study, 120 watersheds are collected to construct a regression model; 85 of these basins are used for regression analysis, and the 35 remaining basins are utilized to verify the feasibility of the constructed model. Random forest algorithm is applied to screen out important geomorphologic factors from the 16 extracted factors that may affect flow velocity. Multivariate regression is used to establish the numerical relationship between velocity and the selected factors. Sensitivity analysis of each adopted factor in the constructed model is conducted using the LH-OAT method. The rationality and feasibility of the regression model are validated by comparing the flow velocity calculation with a previous approach, which is also calculated based on geomorphological parameters. Subsequently, the runoff simulation based on the GIUH model is evaluated using the proposed technique. Results demonstrate that the proposed formula possesses high fitting accuracy and can be easily used to calculate flow velocity and generate GIUH.

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Understanding and managing uncertainty related to future change in catchment systemsdefining and developing Best Practice Guidance

There are increasing demands to predict the response of catchments to future change whether due... more

Evaluating strategies for adaptation investment in a highly variable climate

Role of hydrology in managing consequences of a changing global environment, 2010

A response to 'Climate stability: An inconvenient proof' by Bellamy, D. and Barrett, J

A restatement of the natural science evidence concerning catchment-based ‘natural’ flood management in the UK

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2017

Flooding is a very costly natural hazard in the UK and is expected to increase further under futu... more Flooding is a very costly natural hazard in the UK and is expected to increase further under future climate change scenarios. Flood defences are commonly deployed to protect communities and property from flooding, but in recent years flood management policy has looked towards solutions that seek to mitigate flood risk at flood-prone sites through targeted interventions throughout the catchment, sometimes using techniques which involve working with natural processes. This paper describes a project to provide a succinct summary of the natural science evidence base concerning the effectiveness of catchment-based ‘natural’ flood management in the UK. The evidence summary is designed to be read by an informed but not technically specialist audience. Each evidence statement is placed into one of four categories describing the nature of the underlying information. The evidence summary forms the appendix to this paper and an annotated bibliography is provided in the electronic supplementary...

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Response to ‘Engineering Adaptation’

Hydrological Modelling

Rodda/Progress in Modern Hydrology: Past, Present and Future, 2015

Strategic Overview of Land Use Management in the Context of Catchment Flood Risk Management Planning

Pender/Flood Risk Science and Management, 2010

It is widely recognized that, to cope with the impacts on flooding of climate variability and cha... more

James (Jim) Clement Ignatius Dooge (1922–2010)

Eos, Transactions American Geophysical Union, 2010

James (Jim) Clement Ignatius Dooge died peacefully at his home in Dublin, Ireland, on 20 August a... more

Decision-Making for Adaptation Investment in a Highly Variable Climate

Methodologies for determining flood protection investments have traditionally relied on past hydr... more Methodologies for determining flood protection investments have traditionally relied on past hydrological records being stationary and therefore statistically representative of future conditions. Due to climate change, it has been suggested that the hypothesis of stationarity for hydrological time series models is no longer tenable, and that nonstationarity must be invoked. However, while this proposition is very plausible, nonstationarity represents a highly intractable assumption in that it can take many different forms, and the usual processes of statistical averaging used in calculating means, variances and covariances can no longer be invoked. It is suggested that, before stationarity is discarded, its limits should be explored more fully by using stationary time series models that exhibit long-term variability/persistence to explore investment strategies as a function of increasing levels of variability in hydrological time series. One such model, the ARMA (1,1) model, is empl...

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Modeling the impacts of climatic change and variability on the reliability, resilience, and vulnerability of a water resource system

Water Resources Research, 2003

During the last decade, there have been increasing concerns over water resource drought in northe... more During the last decade, there have been increasing concerns over water resource drought in northern England, brought about by the 1995 Yorkshire drought with an estimated 5-month rainfall return period of 200 years. The impacts of climatic change and variability on water resource reliability, resilience, and vulnerability in this region are examined by modeling changes to weather type frequency, mean rainfall statistics, and potential evapotranspiration. Results indicate future improvements in water resource reliability due to increased winter rainfall but reductions in resource resilience and an increased vulnerability to drought. Severe droughts comparable to that of 1995 show only a slight increase in frequency by 2080. However, there are significant increases in both the magnitude and duration of severe water resource drought, as a consequence of summer rainfall reductions and increased climatic variability. This research provides a basis for the future planning and management of the Yorkshire water resource system.

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Earth systems engineering: turning vision into action

Proceedings of the ICE - Civil Engineering, 2007

The potential of technology to help solve many of the world's most pressing problems, ranging... more The potential of technology to help solve many of the world's most pressing problems, ranging from climate change to resource scarcity and poverty, is widely recognised. However, rationally managing and engineering the Earth's systems is a hugely complex task, which extends engineering from its traditional technical domain to dealing with coupled human and natural systems and unprecedented levels of uncertainty. It requires new understanding of how the effects of engineering accumulate and propagate across scales, up to the planetary scale. This paper surveys the challenges and principles of ‘Earth systems engineering’, as a counterpart to the already fast-developing field of Earth systems science. Examples illustrate how engineers are already applying their skills to manage complex systems such as cities, coastlines and climate.

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Physically-based modelling, uncertainty, and pragmatism – Comment on: ‘Système Hydrologique Europeén (SHE): review and perspectives after 30 years development in distributed physically-based hydrological modelling’ by Jens Christian Refsgaard, Børge Storm and Thomas Clausen

Hydrology Research, 2012

The Système Hydrologique Europeén (SHE) modelling system and physically-based distributed modelli... more The Système Hydrologique Europeén (SHE) modelling system and physically-based distributed modelling (PBDM) were discussed in Refsgaard et al.'s Système Hydrologique Europeén (SHE): review and perspectives after 30 years development in distributed physically-based hydrological modelling (Hydrology Research41, pp. 355–377). The opportunity is taken here to correct some oversights and potentially misleading perspectives in that paper and mount a more robust defence of PBDM.

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