1642 research outputs found
Sort by
Creating and testing an approach for upscaling climate services
No full textUpscaling is the process of moving beyond pilots or prototypes to repeatable and/or transferable services that are accessible and useful to stakeholders and users. It may also refer to increasing the provision, reach, or impact of an existing service. Upscaling any service or product is a complex process, which – in the case of climate services – is exacerbated by serving an emerging market, and many projects taking place in academic settings with short term funding cycles. Climate service providers, their delivery partners and funders could benefit from increased reach and impact by explicitly considering how their services can scale and what the enablers and barriers to this may be. This could take the form of reviewing academic literature, applying structured frameworks, or learning from best practice examples.
Here, we describe the process of creating, testing, and refining an upscaling approach for climate services. The resulting approach is presented, alongside case studies that helped update it and provide evidence for its usefulness and useability. This detailed study of upscaling climate services sets the foundation for effective and sustainable provision of climate services beyond pilots and prototypes and further development of upscaling frameworks and tools to this end
Quantifying the flood risk reduction of coastal nature-based solutions in the Caribbean: implications for developing insurance products
No full textTourist-related businesses, which are key to the economies of many small island states in the Caribbean, are often vulnerable to coastal flooding. Nature-based solutions, such as coral reefs and mangroves, can help to reduce their coastal flood risk. There has been a dearth of work accurately quantifying the risk-reduction benefits for mangroves and reefs in the Caribbean and what the implications are for developing insurance products. This paper describes the modelling to estimate the expected annual damage (EAD) for buildings in the Caribbean with and without coastal nature-based solutions in place. Reefs and mangroves have the potential to reduce the EAD. However, in the case of reefs, this effectiveness is related to their health, with unhealthy ones increasing EAD in some cases. One of the limiting factors to developing traditional indemnity insurance products, which take into account coastal nature-based solutions in the Caribbean, is the accurate quantification of the reductions they have on the EAD. However, to develop indemnity insurance products which take account of reefs and mangroves would require significant updates to existing catastrophe models which are used by the insurance industry, as well as tailoring them for specific locations. Parametric insurance products offer a potential mechanism for restoring damaged reefs and mangroves; however, further research is needed to better align payout triggers with the actual damage these ecosystems sustain
Tsunami boulder transport in coastal environments: insights from physical experiments and dimensional analysis
No full textCoastal boulder deposits hold the potential to aid in the reconstruction of past extreme wave events. However, commonly used hydrodynamic equations for calculating wave heights from transported boulders can be inaccurate. New and alternative methods need to be explored in an interdisciplinary way to ensure a more complete picture of the phenomenon of boulder transport is achieved. Through the use of a physical experiment, this study aims to investigate the influence of different tsunami wave types, wave parameters and boulder shapes on boulder transport distance. The experimental results also allow for a novel application of dimensional analysis to enable comparisons with other experiments as well as a field case study. In the experiment an elongate irregularly shaped boulder showed transport distances up to 1 m farther than a cuboid shaped boulder under the influence of the same waves. The irregularly shaped boulder had a predominant transport mode of rolling, whereas the cuboid shaped boulder predominantly underwent sliding transport. Tsunami wave type also influenced boulder transport distances, with N-waves frequently showing greater transport than E-waves of a comparable wave steepness. Key offshore wave and boulder parameters were then compared through dimensional analysis using Buckingham's Pi Theorem, enabling comparisons to other datasets to be made. Data from another published experimental study and a field study in Settai, Japan, showed reasonable agreement, particularly for the shorter period field data. These findings emphasize the importance of incorporating boulder shape, wave type, and dimensional analysis into future studies, providing a foundation for more accurate reconstructions of past tsunami events
Can computational fluid dynamics be the basis for the next generation of breach models?
No full textDam and embankment failures can have devastating consequences for communities, infrastructure, and the environment. Therefore, accurate modelling of dam and embankment breaches is crucial for effective flood risk assessment and emergency response planning to precisely estimate areas and people that are prone to risk and plan for reducing the damage to properties and the environment. Recently, many advances have been made to improve the accuracy of breach modelling, including the development of physically based one and two dimensional numerical models that takes into account the various processes that take place during the breach of an embankment dam or a flood embankment.
This paper presents the recent work that was undertaken at HR Wallingford to further improve the various breach modelling aspects by exploring the possibilities of using Computational Fluid Dynamics (CFD) models to simulate a breach. Although commercial CFD packages exist that can model air-water interaction well, there are none that currently model air-water-soil erosion at a suitable scale. Therefore, this work started by looking first at potential CFD core methods that can be used such as CFD with Discrete Element Method (CFD-DEM), Smoothed Particle Hydrodynamics Discrete Element Method (SPH-DEM), and Material Point Method (MPM) with a focus on their capabilities to simulate the complex breach processes. Example cases of using CFD-DEM are presented showing the challenges in setting up CFD models, selecting the various parameters required for such models and computational power needed to run a simulation. Based upon that, a number of near future and long-term recommendations for the use of CFD for breach modelling are made to contribute to the development of more accurate and reliable tools for assessing the potential impacts of dam and embankment failures
Experimental investigation of mixed sand and gravel beach morphodynamics
No full textMixed sand-gravel (MSG) beaches are recognised for the coastal protection they provide, capable of dissipating up to 90% of the incident wave energy. They can be fully mixed or composite (i.e. gravel upper foreshore and sandy lower foreshore) and exhibit a wide range of morphologies. MSG beaches are reported to act morphodynamically different to gravel beaches with a composition 25-40% gravel. Previous flume and field research have, however, been limited to a number of sand-gravel mixtures. This work investigates beach morphodynamics for pure sand to pure gravel, and a range of sand-gravel mixtures.
In a controlled manor, a series of mobile bed experiments were conducted. In each experiment the initial water level, incident wave timeseries, and bed slope were kept the same. The percentage of gravel in the initial bed, however, was increased from 0% to 100%, at 20% intervals, between the experiments. Throughout the experiments water level timeseries, wave-induced pore pressures and near bed wave-induced velocities were recorded. An overhead camera was also used to capture the wave run-up. Bed scans were conducted and sediment samples collected at the start and end of the experiments.
The experimental results demonstrate the influence the proportion of gravel in the bed on the resulting beach morphodynamics, and the effect on the run-up and protection provided by the beach in terms of wave dissipation/reflection. No clear tipping point is observed in the morphodynamic behaviour of the beaches and the beach composition is shown to have a strong influence on the measured run-up
Satellite enhanced computational modelling of underwater noise and ecological impacts in coastal areas
No full textUnderwater sound modelling has become an essential approach for understanding and mitigating noise pollution from human activities in the marine environment such as shipping, construction, dredging and mining. It is now an important aspect of Environmental Impact Assessments (EIAs), yet the lack of comprehensive baseline noise data significantly limits our ability to assess and understand the impacts of marine activities and proposed new developments on the underwater soundscape.
Much of the long-term background (ambient) noise generated in the marine environment is generated by vessel activity in combination with natural sounds generated by weather (rain, wind and waves). We propose a novel computational model to incorporate Automated Information System (AIS) vessel data and weather data from the ERA5 global reanalysis dataset to provide accurate spatial predictions of the ambient noise sound spectrum. AIS data itself does not provide direct information on vessel noise emissions, posing challenges for accurate noise characterisation. To create a robust model for predicting underwater ambient sound maps for vessels in ports and harbours, a comprehensive evaluation of existing vessel noise source level spectrum models was first conducted, encompassing statistical approaches, and empirical models dependent of vessel characteristics (e.g. length, speed, type) and operational conditions. Notably, these source level models often yield different predictions for the same scenario, highlighting the need for a unified framework for underwater noise predictions.
Due to its extensive field validation, the JOMOPANS-ECHO model was chosen as most suitable for modelling the sound source levels for moving vessels, which are dominated by propellor noise. A limitation of this model is that it does not account for engine noise. Hence, on its own, it is not suited to creating noise maps in coastal areas (particularly harbours) where many boats are moored or manoeuvring slowly. To overcome this limitation, we incorporated a second noise source model to account for the machinery noise, based on engine characteristics (e.g. engine mass and number). However, depending on the types of the AIS data available, and because of data gaps being present, these parameters are not always available. To fill these data gaps, an existing regression relationship was used to derive the most common engine characteristics using the available vessel length, speed and type information, allowing the model to be adapted to various types of AIS data. Using Falmouth Harbour (UK) as a test case, the modelled vessel source level spectra were then combined with local bathymetry data and fed into an underwater sound propagation calculation using an acoustic flux formula to generate maps of average vessel noise.
The present study proposes a robust computational underwater noise model, aiming to provide reliable and quantitative prediction for anthropogenic underwater noise, to better support environmental impact assessments for both coastal areas and the open ocean. Further studies will build on the present work by incorporating more complex sound propagation methods to provide more accurate sound level predictions in shallow water environments. Additional regression analysis is also planned, which will improve the model parameter estimation and applicability of the model to the various types of AIS data
Impact of the Mpatamanga dam on sediment budget of the Shire River in Malawi
No full textThe Shire River, originating in Lake Malawi, is an important water resource for irrigation, water supply, ecological functioning of several protected areas and electricity production. A new 358 MW Mpatamanga hydropower project is proposed on the river. This paper describes the sediment studies that were carried out with the aim to (a) improve understanding of the present sediment dynamics in the river system and (b) identifying and quantifying the future sediment impacts of the project. The quantification was achieved by construction of a sediment budget, for which a new method, suitable for circumstances where little information about observed sediment flows is available, was developed. The study was supported by Revised Universal Soil Loss Equation–type sediment yield and soil erosion modelling and long-term reservoir sedimentation modelling to evaluate sediment trapping efficiency. The identified impacts included bed and water level rise affecting assets in the upstream end of the reservoir, storage loss and interrupted sediment continuity towards downstream, in particular for sand-sized particles
Spatial distribution of soil organic carbon in an Irish salt marsh (Rogerstown Estuary)
No full textSalt marshes are globally widespread, found on low-lying coastal shores, and are highly effective at long-term carbon storage; thus, they are vital for climate change impact mitigation. Accurate carbon stock estimation requires an understanding of local-scale spatial variability of carbon storage and the facilitating processes. Few studies investigate the cumulative impact of controlling factors on within-site carbon distribution. This study utilises 60 cores from a salt marsh in Turvey Nature Reserve (Rogerstown Estuary), on the Irish east coast, to investigate spatial variability in soil organic carbon (SOC) content, alongside bio-sedimentary, and environmental factors. Mean carbon density (CD) was 11.1 ± 4.2 kg m−3 at 10-cm depth, ranging from 5.2 to 22 kg m−3 (423% increase) across the marsh. We recommend that to obtain measurements across the full range of the site, for small sample sizes (n < 20), random sampling should be used (mean difference between the site-wide CD and ‘subsample CD’ ranged from 0.04 (n = 10) to 0.29 (n = 5) kg m−3) and marsh edge clustering should be avoided. These results provide the first ever systematic record of local-scale (within ~ 800 m2) SOC and CD variability within an Irish east coast salt marsh and the variation of known influencing factors (including sedimentary and environmental). We also present the first study to systematically provide guidance on capturing marsh-wide SOC and CD most effectively based on limited sampling. The outputs help constrain uncertainties around scaled-up carbon accumulation estimates for regional, national and international inventories
Just around the river bend: the fate of plastic bottle pollution in the Thames Estuary
No full textPreviously considered to be the main pathway of plastic pollution into the marine environment, large river systems are increasingly thought to act as major traps for plastic debris. The River Thames is polluted by plastic debris, including plastic drink bottles, but the proportion of items entering the North Sea is unclear. This study investigates the movement of plastic drink bottles in the Thames estuary using a combination of numerical modelling and in-situ sampling data. The model explores different factors to explain the pathways of the plastic bottles, including the bottle fullness (empty, half-full and full), the wind, and the river discharge (high/low). The model results are validated by in-situ bottle collection data from citizen science cleanups along the banks of the river. Empty bottles are found to be more affected by the wind than the river discharge and more likely to strand along the Thames estuary shoreline. Conversely, full and half-full bottles are more likely to be carried downstream by the residual currents and leave the estuary into the North Sea, particularly during periods of high river discharge. The results suggests that 53 % of full bottles and 41 % of half-full bottles entering the Thames estuary leave the estuary over a 150-days period, contributing to plastic pollution in the marine environment. Understanding the transport and accumulation patterns of debris in rivers, as well as gaining insight into the factors influencing their movement, helps identify optimal clean-up locations to stem the flow of plastic waste entering the marine environment
Model roundup and extension for the current- and wave-induced burial, re-exposure, mobilization and migration of UXO and DMM
No full textThe SERDP funded project MR21-1081 has studied the behavior of UXO (unexploded ordnance) and DMMs (discarded military munitions) under the influence of storm action and morphological change on the shoreface. The mobilization model suite UXOmob was coupled to the scour burial model DRAMBUIE 3.0, which is a strongly improved version of DRAMBUIE. The model was also coupled to hydrodynamic and morphodynamic simulations, using TELEMAC, and applied at the Formerly Used Defense Site at Fort Pierce in Florida, USA