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Land-use change may exacerbate climate change impacts on water resources in the Ganges basin
No full textQuantifying how land-use change and climate change affect water resources is a challenge in hydrological science. This work aims to quantify how future projections of land-use and climate change might affect the hydrological response of the Upper Ganges river basin in northern India, which experiences monsoon flooding almost every year. Three different sets of modelling experiments were run using the Joint UK Land Environment Simulator (JULES) land surface model (LSM) and covering the period 2000–2035: in the first set, only climate change is taken into account, and JULES was driven by the CMIP5 (Coupled Model Intercomparison Project Phase 5) outputs of 21 models, under two representative concentration pathways (RCP4.5 and RCP8.5), whilst land use was held fixed at the year 2010. In the second set, only land-use change is taken into account, and JULES was driven by a time series of 15 future land-use pathways, based on Landsat satellite imagery and the Markov chain simulation, whilst the meteorological boundary conditions were held fixed at years 2000–2005. In the third set, both climate change and land-use change were taken into consideration, as the CMIP5 model outputs were used in conjunction with the 15 future land-use pathways to force JULES. Variations in hydrological variables (stream flow, evapotranspiration and soil moisture) are calculated during the simulation period.
Significant changes in the near-future (years 2030–2035) hydrologic fluxes arise under future land-cover and climate change scenarios pointing towards a severe increase in high extremes of flow: the multi-model mean of the 95th percentile of streamflow (Q5) is projected to increase by 63 % under the combined land-use and climate change high emissions scenario (RCP8.5). The changes in all examined hydrological components are greater in the combined land-use and climate change experiment. Results are further presented in a water resources context, aiming to address potential implications of climate change and land-use change from a water demand perspective. We conclude that future water demands in the Upper Ganges region for winter months may not be met
WireWall: a new approach to coastal wave hazard monitoring
Get PDFWireWall will be the first agile in situ system to make field measurements of overtopping on a wave-by-wave basis. Such data will enable site-specific calibration of (i) numerical tools used in sea defence design, (ii) flood forecasting models and (iii) public safety tolerances used by shoreline managers. The new approach transfers existing laboratory and offshore wave monitoring capabilities to the problem of coastal hazard monitoring. The capacitance wire system will collect high frequency field data to quantify wave overtopping velocity and volume. Our approach will replace the use of water collection tanks, which provide very limited information, are cumbersome, and hence rarely deployed. The method will use a coupled modelling-observational-modelling approach. Industry standard overtopping tools will generate a numerical dataset of plausible overtopping conditions at our study site Crosby (NW England). This data will inform the configuration of the wire units to be used in dockside and flume tests prior to the design of the field rig. The newly collected field observations will allow site-specific calibration and validation of the numerical tools, which will then be applied for a range of storm and beach conditions to develop site-specific overtopping safety tolerances and identify overtopping trigger levels for the existing sea wall
Technical note: comparison of methods for threshold selection for extreme sea levels
No full textExtreme value analysis is an important tool for studying coastal flood risk, but requires the estimation of a threshold to define an ‘extreme’, which is traditionally undertaken visually. Such subjective judgement is not accurately reproducible, so recently a number of quantitative approaches have been proposed. This paper therefore reviews existing methods, illustrated with coastal tide-gauge data and the Generalized Pareto Distribution, and proposes a new automated method that mimics the enduringly popular visual inspection method. In total, five different types of statistical threshold selection and their variants are evaluated by comparison to manually derived thresholds, demonstrating that the new method is a useful, complementary tool
A 3D parallel Particle-In-Cell solver for wave interaction with vertical cylinders
No full textIn this paper, the Particle-In-Cell (PIC) based PICIN solver is extended to three spatial dimensions and parallelised using the Message Passing Interface (MPI) approach. The PICIN solver employs both Eulerian grid and Lagrangian particles to solve the incompressible Navier-Stokes equations for free-surface flows. The particles are employed to carry all the fluid properties, solve the non-linear advection term and track the free-surface, while the grid is used solely for computational efficiency in solving the non-advection terms. Validation of the new 3D model concentrates on test cases involving multiple wave types (including regular waves, focused waves and solitary waves) interacting with vertical cylinders in several spatial configurations. The results are compared with laboratory data and numerical results from state-of-the-art Volume of Fluid (VOF) based Eulerian solvers such as those from the OpenFOAM® suite. It is shown that the 3D parallel PICIN model is able to well simulate highly non-linear water waves, and the interaction of such waves with vertical cylinders, with a CPU efficiency similar to Eulerian solvers. Moreover, the innovative use of particles in PICIN, akin to meshless Lagrangian solvers, gives the model a particular flexibility in handling complex, full 3D, water-wave scenarios involving large free-surface deformations
Chapter 8: Monitoring and data.
No full textWith growing environmental awareness and increasing climate pressures on low-lying deltas, modern-day society puts incredibly strong demands on the sustainability of water infrastructure projects. Classic approaches towards the design and implementation of such projects no longer suffice in satisfying these demands. Recent approaches look beyond the scope of isolated dredging activities and embrace a wider context, by considering water infrastructure development projects as an opportunity to also add value to the (natural and socio-economic) system in order to achieve more sustainable projects. In the past 10-15 years, the international dredging community has embraced this kind of thinking and the approach to dredging has been transformed. From mainly dealing with negative impacts, often at the end of the project design and the start of the construction phase, towards a much more proactive approach where water infrastructure projects are being considered as part of the natural and socio-economic system in which they are situated, and stakeholders are being engaged much earlier in the project development process to facilitate the search for opportunities to create added value. This change in attitude has a huge influence on the initiation, planning and design, execution and maintenance of water infrastructure projects. Comprehensive guidance on how to bring this into practice has to date been lacking. With this book a wide range of professionals have attempted to collect and integrate their experiences and best practices, to deliver this state-of-the-art guidance book on Dredging for Sustainable Infrastructure. Comprised of nine chapters, the book discusses the topics of integrating dredging into sustainable development, sustainability in project initiation, planning and design, assessment and management of sustainability, equipment and methods, dredged material management, models and tools, and monitoring and data
Physical model tests to determine the roughness of stair shaped revetments
Get PDFStair shaped revetments are considered as an attractive alternative for traditional revetments since the surface roughness reduces wave overtopping resulting in a lower required crest height. The specific shape enables easy access from and to the water surface, enhancing the attractiveness for tourists and residents. To implement stepped revetments in the design of a seawall there is a need to quantify the roughness of a stair shaped revetment to predict wave overtopping rates. This paper describes research in which 2D physical model experiments were conducted in Deltares’ Scheldt Flume. Based on the obtained data a method to quantify the roughness coefficient of such structures is suggested
Advances in the characterization of pressures and velocities in the overtopping of arch and gravity dams
Get PDFWhen dams overflow, they produce free jets that discharge into plunge pool basins. The pressure and velocity distributions of the flow in the plunge pool must be estimated to evaluate the potential scour that might destabilize the dam. In Protections 2016 event (Fort Collins, Colorado, USA), the first two authors presented results of free falling jets in plunge pool, comparing numerical results against experimental data. Instantaneous pressures, velocities and air entrainment were obtained with piezoresistive transducers, Acoustic Doppler Velocimeter and optical fiber, respectively. To identify the level of reliability of models, numerical simulations were carried out by using the “homogeneous” model of ANSYS CFX, together with different turbulence closures. Castillo et al. (2015) established different equations to calculate the jet energy dissipation in the air and in the water cushion, as a function of the Y/Bj and H/Lb ratios (where Y and H denote the depth of the water cushion at the plunge pool and the total head, respectively, and Lb is the break-up length). This paper includes further measurements that complete the range of flow tested. New adjustments and analysis are presented in the mean, fluctuating and extreme dynamic pressure coefficients. Furthermore, velocity and turbulent kinetic energy profiles have been obtained. The energy dissipation in the air and in the plunge pool has been also analyzed
Successful overtopping protection projects in the Eastern U.S.
Get PDFThe two most commonly used systems for erosion protection of embankment dams and earthen spillways in the United States consist of roller-compacted concrete (RCC) and articulating concrete blocks (ACB). Schnabel Engineering has designed and observed the construction of nineteen RCC and eleven ACB armoring projects during the past 20 years. These overtopping protection systems are most frequently selected as economic solutions to address various spillway deficiencies, in lieu of more conventional alternatives. This paper tabulates the basic details of each project, including project name, location, completion date, armoring height, and design depth of overtopping. Three RCC projects and three ACB projects located in the eastern U.S. are then highlighted to provide additional design details (including project cost) and present unique aspects and challenges associated with each project. Finally, the successful performance of one of the RCC projects during an estimated 25-year storm event in September 2009 is described. The information presented in this paper regarding the design application, installation, and performance of RCC and ACB overtopping protection systems in the eastern U.S. should be of interest to engineers involved with dam safety and erosion protection systems worldwide
Flood Risk Management in the United Kingdom: Putting Climate Change Adaptation Into Practice in the Thames Estuary (Chapter 6)
No full textLondon and the Thames Estuary’s floodplain in the southeast of England are susceptible to flooding from storm surges. They are protected from floods with a return period of up to 1000 years by the Thames Barrier and a series of flood defences. Owing to climate change the Thames Barrier and its associated defences will need to be upgraded to maintain the same level of protection. The cost and irreversibility of the potential investments means that the investments in future flood defence infrastructure are sensitive to climate change and that the potential for maladaptation is significant. In 2002, the Environment Agency, the organization responsible for flood risk management in England, established the Thames Estuary 2100 (TE2100) project with the objective of developing a strategic flood risk management plan for London and the Thames estuary through to the end of the century. The approach to flood risk management presented in the TE2100 plan included a method of developing options together with a regular updating process in which options and decisions are reviewed taking account of changing circumstances. TE2100 was the first major flood risk project in the United Kingdom to have put climate change adaptation at its core. There is scope for the adaptation pathways methodology utilized in the TE2100 to be used by planners in other situations where a lack of information creates uncertainties