1642 research outputs found
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The MAKEWAVES tsunami collaboration
No full textMAKEWAVES is an international multi-partner collaborative project bringing together six academic institutions and two commercial consultancies. Their objective is to overcome the inherent problems for long term research projects that don’t naturally attract significant domestic funding, but which may ultimately lead to internationally accepted guidance for structural codes or standards
Humber 2100+: resilience and adaptability at the strategic scale
No full textThe publication of the new national Flood and Coastal Erosion Risk (FCERM) Strategy in England sets out a vision of a nation ready for, and resilient to, flooding and coastal change – today, tomorrow and to the year 2100. This ambition needs to be turned into reality for those at risk of flooding and coastal change both now and with a changing climate. Humber 2100+, a tidal strategy to manage risk against a backdrop of economic growth and development in a sustainable way, is a project leading how we implement that ambition. Humber 2100+ is balancing working in partnership with limited funding to deliver an adaptive pathway to manage flood risk over the coming years, exploring what is necessary for the region to be resilient in a changing climate. Resilience will require a broad spectrum of measures from flood warning and evacuation, through to changes in planning and defence improvements. In the short-term Humber 2100+ will deliver a substantial programme of investment in both defence improvements and resilience measures to enable the implementation of an adaptive pathway in response to rising sea levels and climate change. We are working with our partners and are seeking to have all the technical work (including consultation) completed by the end of 2023 prior to embarking upon an approval and adoption process
Field measurements of cable self-burial in a sandy marine environment
No full textThe world's shallow continental shelves are currently experiencing a rapid pace of development from the growth of offshore renewable energy. The emplacement of infrastructure on the seabed can change the morphology of the bed, the nature of the flow above it and transport of sediment and so complicate the assessment of seabed stability for planning and designing offshore renewable infrastructure. To ascertain how much of an impact these natural processes have on cable stability, we present the first field observations made directly over a section of subsea cable, from two deployments in the Eastern Irish Sea at a location of current and planned offshore windfarms. Profiles of flow, turbulence and suspended sediment concentration were measured over a section of typical high voltage electricity cable. Upon deployment our observations show that sediment was deposited around the cable and self-burial occurred. The rate of deposition varied between surveys dependent on forcing and local bed conditions. Turbulence generated from the cable itself reduced as the embedment depth increased, but the relationship between bed shear stress and suspended sediment concentration was not consistent between surveys. We discuss several processes potentially responsible for the prevalence of deposition around the cable, and the difference in seabed mobility between the surveys
An innovative wave overtopping measurement system to calibrate numerical flood hazard assessment and alert tools
No full textIn the UK £150bn of assets and 4 million people are at risk from coastal flooding, whilst the construction of sea wall defence schemes typically cost at least £10,000/m. With reductions in public funding, rising sea level and 3200 km of coastal defences (i.e. about £3bn), cost savings are required that do not reduce flood resistance. The design of new coastal schemes and the setting of tolerable hazard thresholds requires site-specific information of wave overtopping, but this information is very rarely available from in situ measurements.
The National Oceanography Centre converted an existing wave measurement technology into a prototype overtopping measurement system "WireWall" to obtain wave-by-wave observations of overtopping velocity and volume. The system was validated against collection tanks in HR Wallingford’s flume and compared with BayonetGPE predictions. Successful trials followed at Crosby, North West England, collecting quantitative data to calibrate/validate: 1) overtopping tools; 2) flood forecasting services; and 3) site-specific safety tolerances.
Multiple WireWall systems have since been deployed at Dawlish and Penzance, South West England, for up to 12 months. Addition of new on-board processing algorithms and telemetry now enables observation-based overtopping hazard to be nowcast (within 15 minutes of detection) via the British Oceanographic Data Centre
Numerical modelling of pump intakes: compliance with standard performance criteria
Full text linkIn this work, we attempt to address some of the key questions regarding the applicability of CFD modelling for assessing the hydraulic performance of pumping installations and demonstration of compliance of the design against the criteria described in the ANSI/9.8-HI standards. We do this by re-visiting past experiments of pumping stations performed in HR Wallingford’s laboratory and repeating these tests using CFD simulations with OpenFOAM. Existing workflows and analysis methods are used and new ones are proposed to assess the velocity profiles and swirl angles at the pump intakes and to characterise the relative strength of surface and subsurface vortices. Results show that the CFD model results can reproduce experimental data relating to the variation of velocity at the pump suctions within an average difference of ~2% and a maximum difference of ~4%, with the CFD model output showing a tendency to slightly overestimate the velocity profile variation. CFD output of swirl angles shows a good agreement with experimental trends as an overall indicator of facility performance, whilst variations were evident at individual pumps. The methodology proposed to assess CFD model results with respect to classification of surface and subsurface vortex strength presents a good correlation with laboratory observations. In overall terms, a good correlation between physical and CFD modelling results is achieved for assessing hydraulic performance of pump intakes against swirling flow, in the context of performance criteria described in the ANSI/HI-9.8 standards. The uncertainties of the methodology are also captured and further discussed
Forecasting tropical cyclone surge
No full textTropical cyclones, with strong winds and low central pressure, can produce very large coastal surges and have led to the most devastating flooding in history. For example, in Bangladesh, flooding from cyclones in 1970 and 1991 has been estimated to have cost the lives of over 300,000 and 150,000 people respectively. While forecasting of cyclones and emergency management have improved dramatically, flooding from cyclone surge still represents one of the most serious global natural hazards and a considerable challenge for humanitarian organisations.
In 2020, Cyclone Amphan was forecast to make landfall on the border of Bangladesh and India and the UK Foreign, Commonwealth and Development Office (FCDO) approached HR Wallingford to provide a forecast of the potential cyclone surge. Following that event, the FCDO commissioned a pilot study to develop the forecasting of flooding globally, including surge modelling, response of rivers to rainfall, modelling of flooding from both fluvial and coastal sources and analysis of the impact on local population and infrastructure. The aim of the forecast is to provide advance warning of the location, extent and severity of flooding and impact on population in order to aid the coordination of humanitarian relief. The service is provided by a partnership of ECMWF, the Universities of Reading and Bristol, Fathom and HR Wallingford.
As part of this service, a surge forecast system was developed using TELEMAC-2D forced by cyclonic wind and atmospheric pressure fields. The development of the system had to overcome a number of challenges:
• The TELEMAC-2D models have to be large enough to cover all areas of interest to the FCDO and humanitarian agencies and at risk of flooding from cyclone surge;
• The models must adequately resolve the wind and pressure fields of cyclones and coastal bathymetry and topography;
• The models must include tide as it is the combination of both tide and surge that determines the elevation of the water and hence the extent and severity of flooding;
• The models must run quickly. The goal is to provide a bulletin within one working day and the target for the surge model runtime is less than one hour.
The surge modelling system includes a number of regional TELEMAC-2D models covering areas of the world vulnerable to cyclone surge flooding and of interest to the FCDO. The regional models include tide and atmospheric forcing. Cyclone tracks are downloaded from relevant meteorological agencies responsible for forecasting tropical cyclones. Within the modelling system, these are converted into wind and pressure fields to force the model. Model results are extracted along the coastline for input into an inundation model and population exposure analysis. The combined results showing areas forecast to be affected by flooding and the impact on the local population and infrastructure are summarised in a concise bulletin for the FCDO. The bulletin is then circulated to local and international aid organisations including the UN OCHA and International Federation of Red Cross and Red Crescent.
Since the start of the pilot study in October 2020, the team have responded to tropical cyclones affecting Central America, Mozambique, Madagascar and the Philippines
River Deltas Research - Recent Advances
No full textRiver deltas are among the most sensitive and widely exploited territories habitats on Earth. Although predominantly shallow aquatic environments, river deltas are extremely important environments socioeconomically and their usage places ever-increasing stresses on these habitats, especially where there is any anthropogenic involvement. The effective governance and administration of river delta re..
Impact of the Salt Concentration and Biophysical Cohesion on the Settling Behavior of Bentonites
No full textThe flocculation behavior of clay minerals in aquatic environments is an important process in estuarine and riverine dynamics, where strong gradients in salinity can locally occur. Various contradicting observations have been reported in the literature on the impact of salt concentration on the settling process of cohesive sediments. To address this issue in a systematic manner, we investigate the settling behavior of clay minerals as a function of the salt concentration of the ambient water. Specifically, we focus on montmorillonite as a prototype clay mineral with a high cation exchange capacity (CEC). To this end, we study suspensions of Wyoming bentonite (Volclay SPV) as a very important constituent for many constructional and industrial purposes. We perform an experimental campaign to study the settling behavior of moderately turbid montmorillonite concentrations in monovalent salt solutions with different salinities (sodium chloride) to represent different environments ranging from deionized to ocean water, respectively. The subsequent settling process was monitored by taking pictures by a camera in regular time intervals over a total observation time up to 48 h. In addition, a modified hydrometer analysis is conducted to determine the grain size distribution (in terms of an equivalent diameter) of the flocculated clay suspension in salt water. Despite the rather high cation exchange capacity of the investigated clay (CEC=88.1), our results show that the settling speed drastically increases within a range of 0.6–1.0 PSU and stays approximately constant for higher salinities. This critical salt concentration is defined here as the critical coagulation concentration (CCC) and lies well below the salinity of natural open water bodies. The hydrometer analysis revealed that 60% of the agglomerates exceed the equivalent grain size of 20 μm. Finally, the findings of this study are supplemented with experiments studying the effect of Extracellular Polymeric Substances (EPS) on the flocculation behavior of bentonite in salt water. Our results demonstrate that salinity is the original trigger for flocculation, whereas EPS allows for even larger floc size but it does not play a significant role for the settling processes of bentonite in estuarine environments
National-scale management and protection of desalination plant water supplies
Full text linkFreshwater demand is set to outstrip supply in many parts of the world, with the effects of changing climate, evolving land use, and industrial development. Several countries already rely on seawater desalination as their key source of potable water. Desalination plants require a constant supply of clean seawater, and are therefore vulnerable to pollution from marine outfalls, coastal construction activities, and shipping. National-scale management plans are necessary to ensure that coastal developments and facilities are coordinated to prevent harmful effects on these vital plants, and to protect the environment. This involves management and integration of multiple stakeholders and governing bodies. The authors use multiscale hydrodynamic and pollutant dispersion modelling to provide advice to national water authorities, who are consultees in the permitting processes for new developments close to sensitive desalination plants. In this paper, key strategies of management and mitigation are presented
Sediment transport modelling in Texas: challenging the conventional knowledge on littoral drift direction
No full textThe sediment transport at a regional level along the southern coast of Texas has not yet been analysed in detail. In the existing literature, there is agreement that the net sediment transport direction along the coast of the south of Texas is northward along the coast of the Padre Islands. A numerical model is developed that computes the fully coupled waves, currents and sediment transport in the area using the open TELEMAC modelling system. The results of the model show that our prior understanding of the nearshore littoral processes was incomplete. The combination of stronger ocean currents during high wave events from the north results in a dominant southerly transport along most of the South Texas coast. Only in the northern half of Kenedy County are the residual transport rates to the north. So, where the literature assumes a drift convergence near Kenedy County, the modelling presented here identifies this area as a drift divide