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Water losses from the Sudd
No full textWater losses in the Sudd wetlands of South Sudan have significant effects on water resources available to Sudan and Egypt. These losses increased greatly after the dramatic rise of Lake Victoria in 1961–1964, but investigation into the cause and location of these increased losses has been hindered by the shortage of records after 1963 and their cessation after 1983. By linking flow records at key points within the Sudd with the distribution of vegetation before the rise, analysis of vegetation after the rise can throw light on the distribution of resulting losses and their causes. Although the increased flooding in the upper reaches of the Sudd has been noted, this paper draws attention to greatly increased inundation in the lower reaches, apparently from backwater flooding, which would affect any future proposal for the Jonglei Canal project
Introducing KHIONE – (Eulerian) Part I of the ice modelling component of TELEMAC
Get PDFWith a view to expand the applicability of the TELEMAC system to cold waters around the world, EDF R&D and HR Wallingford jointly financed the development of a new ice modelling component in collaboration with the ice modelling experts from Clarkson University, USA. This collaboration has seen years of experience and ice modelling capabilities of the Clarkson’s team introduced into the TELEMAC system.
Various ice processes can occur in cold regions during winter periods. These include complex interactions between thermal-ice processes and ice dynamics coupled with hydrodynamics. This Part I article introduces those based on the Eulerian assumption. Part II will later introduce processes based on the Lagrangian assumption.
Some of the validation cases developed to demonstrate KHIONE’s capabilities are presented
Application of the Proteus Toolkit to Marine, Coastal, and Riverine Engineering Problems
No full textComputational modeling of wave and current interaction with structures is becoming a reality for engineering analyses traditionally conducted through physical testing. While advances in computational methods have been of primary importance in achieving a robust, accurate, and efficient modeling capability, better algorithms alone are insufficient for realizing the full impact of computational fluid-structure interaction analyses. In this presentation we will present our recent experience attempting to overcome several software engineering barriers through domain-specific extension modules and domain specific languages
Drought and flood mitigation service for Uganda
Get PDFUganda is at high risk from a variety of hazards, which have the potential to adversely affect progress on poverty reduction and economic growth. The World Bank has estimated that at least 200,000 Ugandans are affected by disasters each year. The Government of Uganda has identified drought as the most severe disaster affecting the lives and livelihoods of its citizens.
There are currently significant levels of investment, across Uganda, into systems that collect and share early warning information on a range of hazards including floods and droughts. However, many of the current Early Warning Systems in Uganda do not appear to be sustainable from both a financial and technical point of view. They are mostly based on situational analyses and make little or no use of weather forecast information
Assessing quick-wins to protect critical urban infrastructure from floods. Case study Bangkok, Thailand
No full textThis paper focuses on the vulnerability and protection of critical urban infrastructure from flooding. It presents a pragmatic and rapid screening procedure, referred to as a “Quick Scan”. The purpose of the Quick Scan is to provide guidance for network operators and decision makers on identifying and rating those critical infrastructure networks and hot spot buildings that may be at risk from flooding and assessing where intervention will be most feasible and cost beneficial – the so-called “quick wins”.
This approach will support the development of effective interventions to alleviate direct and indirect flood impacts. Workshops and interviews with stakeholders and experts have been organised in the pilot cities Bangkok, Paris, and Dordrecht to test and further develop the Quick Scan and to obtain feedback and lessons learned for the protection of critical urban infrastructure. This paper presents the findings of the stakeholder workshops carried out in the city of Bangkok
Alde and Ore estuary, U.K. – levee overtopping performance – defence upgrade with 50 km of simultaneous overtopping
Get PDFThe Alde and Ore estuary is protected from open coast attack by the longest shingle spit in northern Europe, extending 17km from Aldeburgh in the north to Shingle Street in the south. The low lying land adjacent to the tidal estuary is divided into a number of flood cells protected by more than 50 km of levees, locally referred to as “river walls”.
Last heightened following a catastrophic North Sea storm surge in 1953 the additional weight of the defences has resulted in significant consolidation settlement, by up to 1m.
With little or no government funding for improvements to the existing degraded defences an innovative approach has been required to ensure an affordable solution. This strategy being given more impetus following a North Sea tidal surge in December 2013, recorded as a 1:17 year event, which left the defences wanting
Application of machine learning techniques to support decision making under uncertainty in water resource management
Get PDFWater companies in the UK are required to produce long-term plans of water resources for their supply area every five years, detailing how they will maintain secure, sustainable supplies , taking account of social and environmental impacts as well as economic costs. Extensive ensemble modelling of water resource systems underpins the production of these reports and the resulting investments chosen to maintain supplies into the future.
Adoption of new guidance on the use of advanced Decision Making Methods (DMMs) and Risk Based Planning has demanded a more comprehensive modelling approach. Modelling and analytical efficiencies are increasingly required for their use and to realise their full benefits. Existing water resources, hydrological, groundwater, and demand models traditionally used by water companies are often not ideally suited for use in these DMMs. Consequently a toolset of approaches is evolving to enable UK water companies to undertake this more complex decision making.
Key elements of this toolset include emulation modelling to complement computationally more expensive process models, machine learning techniques for groundwater assessment and to optimise reservoir control curves considering multiple objectives, and agent based models to explore the spatial and temporal pattern of demand over ensembles of plausible futures. These methods support the rapid simulation times required for applying the DMMs to provide a holistic view of system behaviour under large supply-side, demand-side and policy uncertainties. User-friendly tools and dashboards are being used to explore and communicate the outputs and facilitate effective decision-making, involving all stakeholders.
This toolset of approaches is being increasingly adopted in the UK, demonstrating the potential for innovative methods to interpret and present complex modelling results. Due to the flexible structure of the tools, and the generic approaches used, these techniques can readily be applied to a wide range of settings. However, the absence of physical process representation in some of these methods, and associated implications, must be considered in their application and by planners when interpreting results. Methods in themselves are not a replacement for diligent water planning, but a tool to support it
Protection of embankment dam toe and abutments under overtopping conditions
Get PDFThis article is primarily intended to introduce the theoretical and practical significance of the downstream toe and abutments of embankment dams. Further, summary of previous empirical and experimental research works carried out in the field of embankment dam protection under overtopping conditions is presented. Relationships for sizing of dumped riprap stones at embankment toe are proposed based on key findings from the research areas of design of dumped ripraps and embankment dam toe. The proposed criteria are tested with available experimental data. The paper also aims at bringing to the fore, possibilities for further research
Hydraulic simulators on real dikes and levees
Get PDFThe first part of this chapter gives a short description of wave processes on a dike, on what we know, including re-cent new knowledge. These wave processes are wave impacts, wave run-up and wave overtopping. The second part focuses on description of three Simulators, each of them simulating one of the wave processes and which have been and are being used to test the strength of grass covers on a dike under severe storm conditions. Sometimes they are also applied to measure wave impacts by overtopping wave volumes
A guide to breach prediction
Get PDFEarthen embankments that are categorised as large (15m or greater in height) number in the tens of thousands globally. Embankment dam risk assessment is a vital measure that has been adopted throughout the industry to assess the potential impact that catastrophic dam failures can carry. A critical part of this assessment is the prediction of the breach process, which will determine the reservoir outflow hydrograph. This is crucial for the following stage of flood routing, which aids in flood risk assessment, evacuation planning and land-use planning.
This report provides details of the breach prediction methods available to users, ranging from simple parametric equations to complex multi-dimensional erosion models. These are commonly divided into three categories; parametric models, semi-physically based models and physically based models.
Parametric models, such as Froehlich (2016a, b), Xu & Zhang (2009) and Von Thun & Gillette (1990), allow breach geometry, formation time and peak outflow to be estimated through the regression analysis of historical dam failure data. These have advantages in their ease and speed of use, but were found to have great uncertainty in their application and are therefore not typically suitable for high risk applications, where uncertainties will have a large impact. Appropriate applications include initial appraisal-level breach modelling and the study of low-risk scenarios where uncertainties will have a minimal impact.
Semi-physically based models, such as HEC-RAS, take breach geometry and formation time, or soil erosion rates, as input values to produce a breach hydrograph. No physical processes are modelled; rather the flow of water through the use-defined breach is calculated using simple fluid dynamic equations, such as weir and orifice flow. These provide no improvement in the accuracy of predicting a breach over parametric models, but improve on the process of converting these results into outflow hydrographs, which may be required for further use.
Physically based models, such as EMBREA, DL Breach and WinDAM consider the complex geotechnical, structural and hydraulic behaviour of an embankment dam and its impounded reservoir. While generally more time-consuming than parametric and semi-physical models, physical models tend to provide results with a greater certainty and accuracy. These, as a whole, are suitable for high risk breach scenarios, where accuracy and reliability are critical in providing results within the acceptable bounds of uncertainty.
The descriptions and recommendations of breach prediction methods in this report are intended to guide users towards the most appropriate breach model for a given scenario. A recommended approach to choosing a model type (parametric, physical etc.) is given, taking into consideration the type of analysis and associated risks, amongst other factors.
It was concluded that, while parametric models have tended to be used by industry in the past, technological advancements and practical field testing have allowed rigorous physically based models methods to become more feasible. Further developments are likely to reduce the reliance of physical models on simplifications and improve their accuracy and usability