Paul Sayers

Quantified scenarios analysis of drivers and impacts of changing flood risk in England and Wales: 2030–2100

Abstract Flood risk to the economy, society and the environment reflects the cumulative effects of environmental and socio-economic change over decades. Long-term scenarios are therefore required in order to develop robust and sustainable flood risk management policies. Quantified national-scale flood risk analysis and expert appraisal of the mechanisms causing change in flood risk have been used to assess flood risk in England and Wales over the period 2030–2100. The assessment involved the use of socio-economic and climate change scenarios. The analysis predicts increasing flood risk unless current flood management policies, practices and investment levels are changed—up to 20-fold increase in economic risk by the 2080s in the scenario with highest economic growth. The increase is attributable to a combination of climate change (in particular increasing precipitation and relative sea level rise in parts of the UK) and increasing socio-economic vulnerability, particularly in terms of household/industrial contents and infrastructure vulnerability. The policy implications of these findings are discussed.

Strategic flood management: ten ‘golden rules’ to guide a sound approach

ABSTRACT Over recent decades, remarkable progress in cultivating the concepts of flood risk management has taken place across countries as diverse as India, China, Australia, the UK and the USA. This change highlights a risk management paradigm as potentially more complex than a more traditional standard-based approach as it involves ‘whole systems’ and ‘whole-life’ thinking; yet this is also its main strength – paving the way for more integrated and informed decision-making. Strategic flood management (SFM) uses a portfolio of responses to manage flood risks and promote opportunities ecosystem services. It recognizes the interrelationships between the actions taken and the contribution flood management provides to integrated river basin and coastal zone planning. The paper results from an international collaborative effort for research and distils approaches to flood risk and water management in challenging large-scale and complex environments. The paper provides an overview of the emerging good practice in SFM, including (i) an analysis of the flood events that have shaped changes in approach, (ii) the purpose and characteristics of modern SFM, (iii) the goals, objectives and outcomes sought and (iv) the challenges associated with implementation (together with some of the common pitfalls and misconceptions). Our conclusions are encapsulated in a set of ‘golden rules’ that underpin sound SFM decision-making.

Time-dependent reliability analysis of flood defences

This paper describes the underlying theory and a practical process for establishing time-dependent reliability models for components in a realistic and complex flood defence system. Though time-dependent reliability models have been applied frequently in, for example, the offshore, structural safety and nuclear industry, application in the safety-critical field of flood defence has to date been limited. The modelling methodology involves identifying relevant variables and processes, characterisation of those processes in appropriate mathematical terms, numerical implementation, parameter estimation and prediction. A combination of stochastic, hierarchical and parametric processes is employed. The approach is demonstrated for selected deterioration mechanisms in the context of a flood defence system. The paper demonstrates that this structured methodology enables the definition of credible statistical models for time-dependence of flood defences in data scarce situations. In the application of those models one of the main findings is that the time variability in the deterioration process tends to be governed the time-dependence of one or a small number of critical attributes. It is demonstrated how the need for further data collection depends upon the relevance of the time-dependence in the performance of the flood defence system.

Managing changing risks to infrastructure systems

Civil engineering infrastructure systems are vulnerable to the effects of natural hazards such as flooding, landslides, windstorm and coastal erosion. Risk analysis provides a rational approach to analysing the threat these phenomena pose and identifying efficient options for system management. This paper presents a general formulation of the risk-analysis problem for an engineering system subject to environmental loads. However, most of the variables that determine system behaviour may be subject to long-term change, for example due to climate change or structural deterioration. The uncertainties in appraisal of infrastructure over extended timescales can be considerable, so a framework is presented for systematic analysis of uncertainties and robust decision making.

Strategic drought risk management: eight ‘golden rules’ to guide a sound approach

ABSTRACT Major droughts are an ever-present threat in almost all countries; a threat that is set to increase in response to climate change and the influence of socio-economic change on the demand for, and use of, water. Historically droughts have been responded to ‘as they happen’ leading to incremental shifts in approach as lessons are learnt. Given the significance of the challenge now faced in this heuristic approach is no longer fit for purpose and a new approach is required. Based upon a combination of expert workshops, detailed international case studies and analysis of past droughts, this paper sets out a strategic approach to managing water resources that specifically addresses drought. The framework encourages a focus on long-term outcomes (for people, ecosystems and economies) and views drought as a water-related risk, not simply a hazard. Strategic drought risk management (SDRM) is presented as a multi-scale endeavour, providing both local and regional solutions whilst addressing short- and long-term challenges. It seeks to implement a diverse portfolio of measures during non-drought conditions as well in the run-up to, during and after a drought event whilst recognizing the critical interdependences between human systems and freshwater ecosystems. The paper concludes by presenting eight ‘Golden Rules’ to guide a sound approach to SDRM.

A framework for strategic river restoration in China

ABSTRACT In response to major water-related challenges, the Chinese government is preparing to significantly expand river restoration efforts. The high level of development in many Chinese river basins requires that this work be undertaken strategically. This article identifies current global challenges to river restoration and presents a framework for strategic river restoration, together with a set of eight ‘golden rules’. The framework and rules were developed specifically to address the Chinese situation, but are relevant elsewhere, particularly for heavily developed and highly contested river basins.

Flood vulnerability, risk, and social disadvantage: current and future patterns in the UK

Present day and future social vulnerability, flood risk, and disadvantage across the UK are explored using the UK Future Flood Explorer. In doing so, new indices of neighbourhood flood vulnerability and social flood risk are introduced and used to provide a quantitative comparison of the flood risks faced by more and less socially vulnerable neighbourhoods. The results show the concentrated nature of geographic flood disadvantage. For example, ten local authorities account for 50% of the most socially vulnerable people that live in flood prone areas. The results also highlight the systematic nature of flood disadvantage. For example, flood risks are higher in socially vulnerable communities than elsewhere; this is shown to be particularly the case in coastal areas, economically struggling cities, and dispersed rural communities. Results from a re-analysis of the Environment Agency’s Long-Term Investment Scenarios (for England) suggest a long-term economic case for improving the protection afforded to the most socially vulnerable communities; a finding that reinforces the need to develop a better understanding of flood risk in socially vulnerable communities if flood risk management efforts are to deliver fair outcomes. In response to these findings, the paper advocates an approach to flood risk management that emphasises Rawlsian principles of preferentially targeting risk reduction for the most socially vulnerable and avoids a process of prioritisation based upon strict utilitarian or purely egalitarian principles.

ALDERNEY BREAKWATER - SCHEME EVOLUTION

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.