1642 research outputs found
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Increasing urban flood resilience through public participation: A case study of Tuti Island in Khartoum, Sudan
No full textOver the past 30 years, Sudan has experienced several severe floods which have caused loss of life and significant damage to property. The frequency and intensity of floods in Sudan are predicted to increase as a result of climate change. The main objective of this research was to assist policymakers in establishing a mechanism for public participation in Sudan to enable communities to be engaged in improving flood risk management. This paper focuses on Tuti Island, which is located near the confluence of the Blue and White Niles in Khartoum which is severely affected by flooding. The research was based on surveys and interviews with both officials and the public to examine the degree of public participation in mitigating flood risks. The research concluded that Sudan has no policy or official way of engaging the public in disaster risk reduction; however, the traditional method of social mobilization called Nafeer (building together) can play a significant role in increasing communities' flood resilience. Establishing a clear framework for public participation, such as Nafeer, for the various stages of the flood management cycle that coordinates with decision-makers can help increase the resilience of urban areas in low-income countries like Sudan
Sediment studies in the Shire River in Malawi
No full textThe Shire River flows from Lake Malawi into the Zambezi River in Mozambique. In the southern Malawi, the Shire is an important water resource for irrigation, water supply, ecological functioning of several protected areas, including the Majete Wildlife Reserve, and electricity production. A new 350 MW hydropower project (HPP) is proposed in the Middle Shire, at Mpatamanga Falls. As every dam, Mpatamanga dam will have an impact on sediment continuity and therefore, on the channel morphology of the Shire River upstream and downstream of the dam. Sediment studies are fundamental to identify and quantify those future sediment impacts by improving our understanding of the sedimentary functioning of the river system. This paper describes the several sources of information and tools available to support the baseline understanding of the Shire River. The tools described include field visits, sediment yield and soil erosion models, geomorphological analysis and sediment budget. Although there are considerable uncertainties in the available data to support quantitative sediment budget estimations, deposition and erosion trends were identified and lessons learnt from the operation of existing dams in the Shire River
Physical modelling of boulder transport under the influence of tsunami waves
No full textTsunami events are traditionally represented in the geological record by a sequence of fine-grained sediments, but increasingly coastal boulder deposits are being used as indicators of past tsunami events. The emplacement mechanism of many boulder deposits, however, is heavily debated and determining whether the inundation event was a tsunami or storm remains an unresolved challenge (Cox et al., 2020). Using physical experiments, we aim to achieve a better understanding of how tsunamis move coastal boulders. This knowledge will aid field geomorphologists in the identification of the emplacement mechanism for coastal boulder deposits and allow for the determination of wave parameters. In January 2023, physical experiments using the HR Wallingford Tsunami Simulator were completed as part of the MAKEWAVES collaboration. These experiments investigated the movement of a cuboid and irregular shaped boulder model when impacted by different tsunami waveforms on a plane beach. We propose new empirical formulae to describe relationships between transport distance and different tsunami waves
The future is transient: Barriers and opportunities for improved UK water resource climate change assessments using the enhanced Future Flows and Groundwater (eFLaG) climate service products
No full textUK water resources face a number of challenges when planning for an uncertain future. Climate change impacts and what future droughts might look like can be a significant contributor to this uncertainty. Recent and potential future developments (e.g. ever-finer resolutions) in climate modelling offer the potential for running bias-corrected transient future scenarios through hydrological, hydrogeological and water supply models, providing users with droughts of differing severity, frequency, spatial extent and duration to those experienced historically, incorporating changes over time and an understanding of climate model uncertainty. The recent enhanced Future Flows and Groundwater (eFLaG) project sought to demonstrate a climate service using these transient scenarios, with the aim of enhancing the resilience of the water industry to drought events and complementing existing approaches. The project demonstrated the use of this transient climate change information within a water resource setting, using a variety of hydrological and water resource models to help illuminate potential gaps and issues with such an approach. If we are to realise the potential of transient scenarios, a number of barriers – both scientific and organisational – need to be overcome. We present a road map for the future based on outcomes from the eFLaG project, as well as ways the eFLaG projections could be used to improve system resilience in the present
Tracking the spatial footprints of extreme storm surges around the coastline of the UK and Ireland
No full textStorm surges are the most important driver of flooding in many coastal areas. Understanding the spatial extent of storm surge events has important financial and practical implications for flood risk management, reinsurance, infrastructure reliability and emergency response. In this paper, we apply a new tracking algorithm to a high-resolution surge hindcast (CODEC, 1980–2017) to characterize the spatial dependence and temporal evolution of extreme surge events along the coastline of the UK and Ireland. We quantify the severity of each spatial event based on its footprint extremity to select and rank the collection of events. Several surge footprint types are obtained based on the most impacted coastal stretch from each particular event, and these are linked to the driving storm tracks. Using the collection of the extreme surge events, we assess the spatial distribution and interannual variability of the duration, size, severity, and type. We find that the northeast coastline is most impacted by the longest and largest storm surge events, while the English Channel experiences the shortest and smallest storm surge events. The interannual variability indicates that the winter seasons of 1989-90 and 2013–14 were the most serious in terms of the number of events and their severity, based on the return period along the affected coastlines. The most extreme surge event and the highest number of events occurred in the winter season 1989–90, while the proportion of events with larger severities was higher during the winter season 2013–14. This new spatial analysis approach of surge extremes allows us to distinguish several categories of spatial footprints of events around the UK/Ireland coast and link these to distinct storm tracks. The spatial dependence structures detected can improve multivariate statistical methods which are crucial inputs to coastal flooding assessments
Comparison of rock-scour protection berm with a shallow foundation under seismic liquefaction
No full textOffshore wind is an ever-growing industry that is key to the future of green energy generation. As new windfarms are built in both seismic and scour prone regions, such as East Asia and North America, there is a need to understand the behaviour of rock-scour protection under seismic liquefaction. Rock dump is a common method to both combat and remediate scour, a phenomenon whereby the redirected water currents from a foundation create vortices which wash away the seabed sediment surrounding the foundation. Rock-scour protection usually consist of a filter layer, smaller rocks to reduce rock-sediment penetration, and armour rocks, larger boulders that resist the force of water. Under seismic loading, loose seabed sand will liquefy and lead to the settlement of rock. However, there is very limited research in this area. This paper presents the results of two dynamic, saturated centrifuge tests. A comparison is made between the behaviour of a scour protection rock berm and a shallow foundation model that exerts a similar overburden stress on the seabed as the rock berm. The main aim is to compare the differences in behaviour between the continuum based shallow foundation model (in the form of an aluminium plate) and a particulate rock berm model. The results show that for small magnitude input motions, the settlement of a plate is greater than that of rock, however, for larger earthquakes, their settlements are comparable, with the plate foundation model settlement being a fraction smaller. This result suggests that some amount of seabed material ingress into the rock berm following liquefaction, leading to slightly larger settlements. These observations from the centrifuge tests can have implications in using continuum based finite element models to estimate liquefaction induced scour settlements. The results presented in this paper form part of a larger research project that investigates the behaviour of rock-scour protection under seismic liquefaction to better aid future design
Assessment of the beach response under the influence of a submerged breakwater using the cross-shore model COSMOS
No full textThe shoreline in Pontecagnano (Italy) is experiencing erosion. A system of submerged breakwaters, covering about 4.5 km length, parallel to the coast, is proposed as coastal protection. HR Wallingford was commissioned by Technital, on behalf of Consorzio Stabile Grandi Lavori S.C.R.L. to undertake a 2D physical model and cross-shore numerical modelling to support the process of selecting of the preferred design option.
This poster sets out the elements of the modelling undertaken to evaluate the different design options in terms of the beach response
Managing risk at Victoria Service Reservoir
No full textVictoria Reservoir is a reinforced concrete service reservoir located in the heart of Bristol. Constructed in 1914, it is one of the oldest reservoirs of its type in the UK. It was constructed on the site of an earlier open service reservoir. During the second world war, the reservoir was damaged and repaired on account of bombs being dropped on it during the Bristol Blitz. In more recent decades, a series of investigations and repairs have been carried out to assess and maintain its structural condition and operational performance. This paper will describe and discuss the various challenges faced by the operator in managing the safety and operational risks associated with a very old reinforced concrete service reservoir
Risk assessment of existing flood detention (storage) reservoirs
No full textThe Environment Agency is carrying out a portfolio risk assessment of their portfolio of around 200 large flood detention reservoirs (FDRs), to inform their reservoir safety management and operation. The ‘Guide to risk assessment for reservoir safety management’ (RARS) was published in 2013 and provides a methodology for risk assessing existing reservoirs in the United Kingdom. It was intended primarily for reservoirs which are normally full, where indicators of poor condition can be observed. It was therefore necessary to extend RARS to cover FDRs, and this paper describes the key elements of the extension to the RARS Tier 1 methodology. It is anticipated similar extensions could be applicable to FDRs owned and operated by other agencies. The next step is to extend RARS for Tier 2 and 3. Washland flood detention reservoirs are in effect partially bunded reservoirs, so some aspects of the approaches adopted here will also be applicable to non-impounding reservoirs
Hurricane surge and inundation in the Bahamas, part 1: Storm surge model
No full textA storm surge model has been developed as part of a pilot study for The Commonwealth of the Bahamas. The hydrodynamic model, TELEMAC-2D, is used to simulate the response of water level to tide and the wind and atmospheric pressure fields of hurricanes and subsequent inundation over land. The model is used by The Bahamas Department of Meteorology to forecast storm surge and flooding over the islands of Grand Bahama and Eleuthera for incoming hurricanes to assist in preparation for and management of hurricane surge events and has been used in a flood risk assessment, reported in a companion paper. The model has been optimised to run quickly while also resolving the bathymetry and topography that affect the development and propagation of storm surge. Wind fields are generated within TELEMAC-2D based on hurricane warning bulletins. The model has been validated for its representation of water level and against tide gauge measurements during four historical hurricanes: Irene, Sandy, Matthew and Dorian. Factors contributing to uncertainty in forecast predictions are discussed and recommendations are provided to improve the performance in future. The pilot study provides a template for future expansion to cover the other inhabited islands of The Bahamas