1642 research outputs found
Sort by
Quantifying the erosion resistance of dikes with the overflowing simulator
Get PDFIt is important to quantify the soil resistance against erosion cause by to the overflow of dikes and levees. Small-scale tests are excluded, due to the lack of similarity for a free-surface flow phenomenon on stepped slopes, with non-established flow and erosion of a cohesive soil. Moreover, using hydraulic laboratory flumes does not make it possible to have a correct representation of the soil in place, in terms of layer compaction. This is why we have developed an on site overflowing device. The device was deployed as part of the DigueELITE research project on a 3.5 m (9.8 ft.) high experimental dike in channels, 60 cm wide (≈2 ft.) and 15 m long (≈50 ft.), covering the downstream slope (1.5H/1V) and the downstream platform. The procedure followed is based on ASTM-D6460 standard. The test campaigns were carried out with flow rates up to 500 l/s per linear meter (0.5 m2/s), water velocity up to 5 m/s, and a discharge depth up to 30 cm (≈12 in.) at crest. Two soil types were studied: lime-treated soil, and untreated cohesive soil. The first phase of erosion is that of the surface layer. The second phase is that of the embankment constitutive soil. The erosion shows a stair-steps pattern, due to the layers of compaction. The results obtained show that lime-treated soil has better erosion resistance than untreated soil. Compared to the untreated soil, erosion in the lower part of the slope is 3 times less in lime-treated soil, and the scour depth development process at the downstream toe is 5 to 10 times smaller. This paper presents the experimental setup, the results obtained, and the perspectives. The most important findings are that overflowing experiments are feasible on site with the proposed test set-up
A new evolution on the wedge-shaped block for overtopping protection of embankment dams: the ACUÑA block
Get PDFThe article summarizes the research studies performed by the Research Group on Dam Safety (SERPA) of the Technical University of Madrid and the International Center for Numerical Methods in Engineering (CIMNE) in collaboration with the company PREHORQUISA. Such studies aim to deepen on the theoretical and practical understanding of wedge shaped blocks (WSB) technology. This research was funded by the Spanish Ministry of Economy and Competitiveness through the research projects called ACUÑA (IPT-2011-0997-020000) and DIABLO (RTC-2014-2081-5). One of the projects goals was to develop a new model of WSB looking for improving the performance of the existing ones. This research led to the new model of WSB called ACUÑA, proprietary in Spain since May 2017 (ES2595852). The paper presents a comparison between the behaviour of the new block with one of the existing models, specifically ArmorwedgeTM. Such comparison has been made using physical and numerical modelling, studying the hydrodynamic pressures on the block and the leakage flow through the joints between blocks and the aeration vents
Managing legacy infrastructure into the future: the River Winster and Meathop Drain flood risk
Get PDFThe completion of the Ulverston and Lancaster Railway in the 1850s included the Arnside viaduct and an embankment on the northern side of Morecambe Bay enabling the railway to reach Grange-over-Sands. The embankment was built across the mouth of the River Winster and resulted in a change to the tidal inundation pattern of the mudflats and saltmarsh area protected by the embankment. The protected area was reclaimed and is now partially developed to include valuable agricultural land, residential properties and a golf club, as well as vital transportation and utility infrastructure.
The sand within Morecambe Bay is extremely mobile causing the migration of drainage channels and has resulted in the construction of training walls for the two main discharges, the River Kent and River Winster, to enable efficient drainage into the bay. The River Winster is further controlled, as it flows under the embankment, by tidal gates that have been modified over the past 100 years. Since its construction the embankment has performed effectively as a coastal defence and still currently provides protection against significant coastal events. In recent times however the flood risk on the landward side of the embankment has increased from fluvial events and is anticipated to increase further due to climate change and other external factors. This paper will examine the possible causes of the increase and concludes that it is the natural processes of the estuary that have resulted in the increased flood risk. The implication for the future management of the embankment and river channels is also discussed
Pneumatic long-wave generation of tsunami-length waveforms and their runup
No full textAn experimental study is conducted using a pneumatic long-wave generator (also known as a Tsunami Generator). Scaled tsunami waveforms are produced with periods in the range of 5–230 s and wave amplitudes between 0.03 and 0.14 m in water depths of 0.7–1.0 m. Using Froude similitude in scaling, at scale 1:50, these laboratory waves are theoretically dynamically equivalent to prototype tsunami waveforms with periods between 1 and 27 min and positive wave amplitude between 1.5 and 7.0 m in water depths of 50 m. The purpose of these tests is to demonstrate that the pneumatic method can generate long waves in relatively short flumes and to investigate their runup. Standard wave parameters, (free-surface, wave celerity and velocity profiles) are used to characterise the waveforms. It is shown that for the purpose of runup and onshore ingression, minimal interference from the re-reflected waves is observed.
By generating tsunami waveforms with periods greater than ≈ 80 s (≈9.5 mins prototype scale) the available experimental data set is expanded and used to develop a new runup equation. Contrary to the shorter waves, shoaling of these longer waves is insignificant. For waveforms with periods greater ≈ 100 s the runup is best described by wave steepness not potential energy. When tested against available runup equations the results are mixed; most perform poorly for scaled tsunami length periods. A segmented regression analysis is performed on the data set and an empirical runup relationship is provided based on a new parameter termed the ‘Relative Slope Length’.
The tests show the definition of offshore wave amplitude is non-trivial and may greatly affect the predicted relative runup of a given wave. It is noted that this appears to be a general issue for all types of tsunami simulation in the laboratory. Together these observations and proposed runup model provide a framework for future numerical studies of the topic
A generic and practical wave overtopping model that includes uncertainty
Get PDFMean wave overtopping discharge is generally accepted to be a primary design criterion for assessing the performance of coastal structures. It is a boundary condition for many coastal flood risk assessments. Modern methods for assessing wave overtopping discharges and their consequences are well documented and reported. Among the various tools available for assessing wave overtopping, the use of artificial neural networks has become increasingly popular. This paper introduces the next stage in the development of these models. Using the same source data, the new generic meta-modelling overtopping model reduces uncertainties and gives clear guidance on the range and validity of the outputs
Supporting the Integration of Climate Resilience in the Water Supply Sector in the Caribbean - training manual
Get PDFAccess to safe, reliable and resilient water supply services contributes significantly to the achievement of national development goals and agendas. Improving the resilience and robustness of water supply services will reduce operational risks associated with climate variability and change and increase the extent to which operational services are able to meet target levels of service.
This Training Manual is intended to support national-level processes in the Caribbean for the integration of climate resilience in the water supply services sector. A generic approach is presented that can be modified and adapted to meet individual country contexts and needs. To support this approach, the Training Manual includes Guidance Materials on good practice methodologies, tools and approaches that are widely applicable in the Caribbean context. Its use aims to internalise and institutionalise good practice.
Application of the Training Manual also aims to strengthen the capacity of national professionals and practitioners responsible for the establishment of robust and implementable climate resilient policies, investment plans and financing strategies
Infragravity seiches in a small harbour
No full textA method is developed to estimate harbor seiche at Marina di Carrara, Italy, from the properties of wind-generated incident waves outside the harbor. A linear model of the spatial structure of amplified seiche modes is combined with empirical estimates of the response of each mode to variable incident wave forcing. These empirical coefficients parameterize the complex nonlinear transfer of energy from wind waves to lower frequency seiche. As at other small harbors (<1 km2 surface area) on ocean coasts, and consistent with previous analyses at Carrara, the observed seiche is relatively energetic at several periods between about 1 and 15 min that are highly amplified theoretically, and the spatial structure of modeled and observed seiches agree as well. The longest seiche (≈15 min) mode is almost spatially uniform within the harbor and dominates with low-energy, short-period incident wind waves (measured 1 km offshore of the harbor). Increased wave energy and longer periods excite shorter period (1–3 min) seiche modes with more complex spatial structure, including small areas of high amplification, which have led to operational issues. The energy in each of the six most energetic seiche modes is related in this paper empirically to offshore incident wind wave height and peak period, allowing detailed predictions of harbor seiche from routine wind wave forecasts. The approach appears applicable to relatively small, shallow harbors with reflective quay walls, in which the exterior harbor mouth is exposed, and the interior sheltered from energetic wind-generated waves
Systematic geophysical and geotechnical embankments survey in the area of the Humber Estuary and Yorkshire
No full textIn the past 10 years, the eastern part of central England has repeatedly been affected by sudden floods caused by extreme climate events, such as tidal waves increased by storm surges, or heavy rainfall. In many areas, levees were damaged from overbank flow or breached as a consequence of overtopping or erosion taking place within the levee or in the underlying materials. It has therefore been necessary to repair or raise the levees in selected areas. In order to properly design and perform the renovation of the levee system, it is important to determine its existing condition, particularly the material composition, foundation conditions and occurrence of local inhomogeneities in the levees, such as old unknown drains, buried pipes and utilities, old riverbeds and material heterogeneity. The optimal approach for these purposes appears to be the combination of a geophysical and a follow-up geotechnical investigation.
Since 2014, systematic geophysical surveying of the levee system in the Humber estuary and Yorkshire has been carried out. Up to the present time, approximately 146 km of levees have been surveyed. This report provides a description of the survey methods entitled GMS (Geophysical Monitoring System) that combines quick and effective methods for general levee description (e. g. the Slingram method) and methods providing detailed description of the characteristic as well as anomalous sections (e. g. electrical resistivity tomography – ERT, spontaneous polarization method – SP). By way of example, several results from the geophysical measurements and their comparison with the results of the follow-up geotechnical drilling investigation are presented as well. The investigation results have been imported into the GIS of the levee manager, which will facilitate their future utilisation. In this way, repeated geophysical measurements can be planned to detect changes taking place after the levees have been repaired or to examine the condition of selected problematic areas under flood loading. This approach has potential to make a significant contribution to ensuring the continued resilience of earthen flood levees and the communities they protect, across the globe
CFD modelling of coastal engineering applications using Proteus toolkit
No full textWith the recent advances in computer technology and the increasing availability in computational resources, the application of computational fluid dynamics (CFD) models to address coastal engineering problems has become practical. In this work, we present the use of the open-source CFD toolkit, Proteus [1] to model coastal engineering applications, emphasising on complex wave-structure interaction processes
Green approaches in river engineering - supporting implementation of Green Infrastructure
Get PDFWorking together with natural systems, which are powered by a diversity of life within them, provides a range of benefits to society, ranging from carbon storage, clean water and air to reduction of climate change impacts and protection against floods and other environmental hazards. This realisation has led to the concept of Green Infrastructure (GI): a network of natural and semi-natural features that intersperses and connects villages, towns and cities. Rivers are part of this green network, which has the potential to provide higher resilience and cost-effectiveness as well as more social and environmental benefits than conventional infrastructure.
This document focuses on river engineering (which is concerned with river works) and therefore, we consider the river or watercourse as a natural or semi-natural corridor or infrastructure element. In this context, GI approaches are those that promote the conservation or restoration of the natural (green) character of our rivers. These approaches are fundamental to improving the water quality, morphology and ecosystems of rivers as well as contributing to an overall strategy to help people and communities adapt to the impacts of climate change