The following are summaries of papers published in other parts of ICE Proceedings during 2004 that readers of Maritime Engineering may find of interest. Non-subscribers can buy any paper using our pay per view service for £17 or $33 per paper. Summaries of all papers in ICE journals are also freely available and fully searchable at the ‘journals on-line’ section of the ICE website at www.ice.org.uk/jol.
Dismantling the Maureen platform—an overview
P. Broughton, R. Davies and M. Green
Proceedings of the Institution of Civil Engineers—Civil Engineering, 157, No. 2, May, 79–85
Removing, dismantling and recycling the world's largest steel gravity platform has proved that the energy industry can safely and sustainably decommission its vast offshore infrastructure when the oil runs out. Nearly 100% of the 110 000 t Maureen platform and its associated 9000 t loading column was either re-used or recycled—with major structural components being used to build new port facilities and 42 000 t of steel landed ashore for scrapping. This paper reports on the complex and delicate task of cleaning and progressively dismantling the vast structure in a Norwegian fjord. It was the final phase of a £150 million decommissioning project, which has now set a benchmark for over 200 other steel structures currently operating in the British sector of the North Sea.
Reuse of materials in coastal and river engineering
J. D. Simm, M. J. Wallis, K. J. Collins and R. Atkins
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 157, No. 3, September, 113–121
The increased demand for materials for flood and coastal defences as sea levels rise and rainfall increases should be reflected by a sustainable use of natural resources. Recycled and secondary materials offer significant potential to reduce the demand for primary materials, but the way in which this is done in a sensitive water environment will be of interest to the whole of the construction industry. The paper examines five criteria that should influence choices between materials options for projects: whole-life costs, technical efficacy, impact on the local environment, environmental impact of materials production and procurement policy. The latter is examined in the context of the sensitivity of the procurement of tropical hardwoods, which are in particular demand because of their durability. A case example is given of the reconstruction of the fire-damaged Southend Pier in which reclaimed tropical hardwoods were imported from the Netherlands for most of the work. Finally, two examples of the reuse of tyres in baled form are examined. One example looks at the technical advantages of using these recycled materials in a flood embankment project and the other at a pilot project to examine and try to allay concerns about leachates from the tyre material.
The recycling and alternative uses of marine sediments
N. J. Cooper
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 157, No. 3, September, 123–130
The theme of this special issue, the reuse of materials, can apply to: (a) the recycling of marine sediments from areas of natural deposition to replenish denuded frontages elsewhere; or (b) the alternative uses of otherwise waste material derived from navigation dredging activities. Such material reuse in the marine environment can provide environmental benefits, assist in reducing risks from tidal flooding or coastal erosion if used in foreshore recharge schemes, or cost-effectively provide construction resources. This paper considers drivers behind reuse of materials in the marine environment, identifies the opportunities and constraints to its application, and discusses key sustainability aspects of these approaches, such as economic, social and environmental issues. Example case studies are provided of two alternative use schemes and one sediment recycling scheme, highlighting both the practical benefits and the practical complexities of these approaches, depending on the specific situations in which they are set.
Artificial reef in Newquay, UK
A. Weight
Proceedings of the Institution of Civil Engineers—Municipal Engineer, 157, No. 2, June, 87–95
A proposal to build an artificial reef has been put together for Newquay in Cornwall. The aim is to enhance surfing conditions for local surfers, to attract visiting surfers and to provide a spectacle for other tourists, particularly during the autumn, winter and spring months. The message nowadays is that engineers should play a wider role in meeting the needs of society, that they must become key practitioners of sustainable development and that they should gain greater recognition for the role they play. It is considered that this proposal goes some way to delivering these goals. This paper discusses the project in the context of sustainable development.
Coastal defence—current UK practice
M. Wright
Proceedings of the Institution of Civil Engineers—Municipal Engineer, 157, No. 3, September, 147–155
Coastal defence is a composite term covering both coast protection and sea defence, with these activities now being actively managed by the various authorities involved, to comply with the Government's policy to ‘reduce the risks to people and the developed and natural environment from flooding and coastal erosion by encouraging the provision of technically, environmentally and economically sound and sustainable defence measures’. This paper shows how the various authorities actively involved in the overall management of the coastline have increasingly worked together to achieve this strategic policy requirement.
Flooding scenarios due to levee breaking in the Po river
F. Aureli and P. Mignosa
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 1, March, 3–12
The results of mathematical modelling of three flooding scenarios due to levee breaking in the middle Po river (northern Italy) are presented. In this area some catastrophic floods that occurred in the nineteenth century caused the formation of several levee breaks and the inundation of wide plains (500–600 km2), with considerable water depths (6–7 m). The inundation dynamics as a result of a levee break occurring at different locations along the right river bank of the Po river were modeled using as upstream boundary condition a synthetic design hydrograph of 200 years return period. The hypothetical breaches were located where the historical ones occurred more frequently or where the more severe consequences of the flooding were expected. Three scenarios were numerically simulated with a two-dimensional mathematical model based on the shallow water equations solved by means of the well-known MacCormack finite difference scheme. When possible, a calibration of the model parameters on the basis of the available information about recent and historical events was performed. The fairly good agreement between computed results and historical data suggests that the proposed approach is capable of reproducing the main characteristics of the phenomenon, giving support to the design of flooding maps for risk assessment.
Conveyance of a managed vegetated two-stage river channel
R. H. J. Sellin and D. P. van Beesten
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 1, March, 21–33
This paper describes the results obtained from a five-year study of a two-stage river channel with a managed floodplain, in the south of England. Water levels at five sections, as well as the discharge, have been measured and recorded at 15 min intervals. Analysis of these data reveals that the resistance coefficient for this reach varies both annually and with the seasons. These variations are shown to be due to the annual cycle of vegetation growth both in the channel and on the floodplain. Some 100 storm events have been recorded during this period. Resistance coefficient values, based on Manning's n, are evaluated for overbank, bankfull and low flows in the channel. A qualitative and quantitative assessment of the channel's behaviour is given, demonstrating the relationship between conveyance and channel conditions for seasonal variation and at different flow depths. A proposal to incorporate this information into a two-stage design method is outlined in connection with river restoration projects and channel maintenance programmes.
Flood hydrographs in open channels
W. H. Graf and Z. Qu
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 1, March, 45–52
For flow in open channels, rating curves are indicators by which readings of the flow depth are converted to discharge. Rating curves have unique relations when the flow is steady and uniform. For unsteady flows, produced by flood hydrographs, rating curves show characteristic loops, implying non-unique relations. In this paper, the passage of hydrographs is investigated, focusing on the basic hydraulic parameters, namely mean velocity, discharge and flow depth, and subsequently on other important parameters, such as friction velocity and friction coefficient. The sequence of arrival of their respective peaks is the subject of this investigation. A limited number of laboratory experiments using a simple channel geometry have been performed and are presented.
Simple modelling of dam failure in a natural river
F. Macchione and G. Viggiani
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 1, March, 53–60
The complex problem of dam failure and subsequent flood estimation is considered. Numerical models are required and distinctive features of natural rivers such as friction and real topography have to be considered. When treating regions of rapidly varied flow, shock-capturing methods are useful and the Saint-Venant equations, in conservative form, should be employed. A number of explicit second-order two-step schemes exist, such as the ‘upwind schemes’. They require non-linear limiters, such as ‘total variation diminishing’ limiters (TVD), to prevent numerical oscillations. ‘High resolution schemes’ are obtained and complex routines have to be implemented. Run time can be burdensome even for one-dimensional calculations. Thus, in this article a very easy to implement scheme, the diffusive scheme, is considered. Stability and accuracy of the numerical solution are analysed and the performances in terms of water depths are tested. The Malpasset dam-break case (France, 1959) is referred to as a test case. Numerical results are compared with the depth measurements of a physical model and with the results of two other numerical models available in the literature.
The influence of impinging jets on hydraulic jumps
Y. Yüksel, M. Günal, T. Boston, E. Çevik and Y. Çelikoglu
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 2, June, 63–76
Experiments were carried out in a horizontal channel with a free jump and jumps with jets introduced at various angles. Particles within the jumps were traced using a high-speed video camera and the images were processed using a computer to determine particle velocities within the jumps. A simple numerical model using Strip Integrals across the flow is used to predict the kinematic characteristics of such jumps. Numerical and experimental results agree satisfactorily. The results show that even a relatively small momentum flux of the impinging jet can profoundly influence the jump in terms of the velocities within the jump and its surface profile. Plunging breakers occurring on a beach as the wave breaks may also be represented as a hydraulic jump with a weak jet impinging at its toe. This study shows that the impinging jet can increase energy dissipation within a plunging breaker.
Clear water scour at abutments
S. Dey and A. K. Barbhuiya
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 2, June, 77–97
Laboratory experimental results on local scour at short abutments (abutment length:flow depth ratio ≤ 1), namely vertical-wall, 45° wing-wall and semicircular, in uniform and non-uniform sediments under a clear water scour condition are presented. The equilibrium scour depth is related to the sediment size and approaching flow depth relative to the abutment length. The equilibrium scour depth increases with decrease in abutment length and increase in sediment size and flow depth. The scour depth is independent of flow depth at higher flow depths. The effect of sediment gradation on scour depth is pronounced for non-uniform sediments, which reduces scour depth significantly due to the formation of an armour layer in the scour hole. The time variation of scour depth for uniform sediments shows a family of parallel lines for different abutment lengths and sediment sizes. For non-uniform sediments, the time variation of scour depth reduces with increase in non-uniformity of the particle size distribution of sediments. The characteristic parameters affecting the maximum equilibrium nondimensional scour depth (scour depth:abutment length ratio), identified based on the physical reasoning and dimensional analysis, are excess abutment Froude number, flow depth:abutment length ratio, and abutment length:sediment diameter ratio. The experimental data in clear water scour condition under limiting stability of upstream bed sediments are used to determine the equations of maximum equilibrium scour depth through regression analysis. The estimated scour depths are in agreement with the experimental data.
Velocity distribution in non-prismatic compound channels
D. Bousmar and Y. Zech
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 2, June, 99–108
River-flow modelling relies on accurate prediction of the stagedischarge relationship. Additionally, the lateral distribution of the longitudinal velocity component should be estimated for sediment transport investigations. In compound channels, the shear stress at the interface between the floodplains and the main channel strongly affects both conveyance and velocity distribution. This effect is reinforced when mass transfer occurs between subsections due to channel non-prismaticity. The stagedischarge relationship and the velocity distribution in prismatic compound channels can be computed using the lateral distribution method (LDM). The present paper investigates an extension of the LDM to non-prismatic channels. The physical meaning of the so-called secondary-current term is discussed. Numerical results are compared with previous velocity measurements in a symmetrically narrowing compound channel and to new bed shear-stress measurements in the same geometry.
An experimental investigation of a horseshoe vortex induced by a bridge pier
M. Muzzammil, T. Gangadharaiah and A. K. Gupta
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 2, June, 109–119
The horseshoe vortex induced at a bridge pier is considered to be one of the principal causes of local scour at the pier. Knowledge of the location, size, shape and rotational velocity of the vortex is of paramount importance in modelling scouring processes and designing a suitable scour protection system. An experimental investigation was carried out to study the dominant features of the horseshoe vortex during the scouring processes with the help of a specially devised vortex probe and a simple method of vortex visualisation. It has been found that the shape of the primary horseshoe vortex is dependent on the pier Reynolds number (ReD). The vortex is of circular shape only at lower Reynolds numbers (ReD ≤ 5000), but it becomes more and more elliptical as ReD increases. The horizontal dimension of the vortex along the mean flow direction has been found to be a function of the pier geometry whereas its vertical dimension is mainly governed by the parameters related to the upstream velocity profile such as the boundary layer thickness. The size of the vortex increases with the development of the scour hole whereas its elliptical shape remains fairly invariant during the scouring process. The mean velocity of the vortex is approximately 50% of the mean approach flow velocity on the rigid bed for 104 ≤ ReD ≤ 1·4 × 105. Its variation with the development of the scour hole indicates an increasing trend in the initial stages of scouring whereas a decreasing trend has been found in the later scouring stages.
Methods for predicting dispersion coefficients in rivers
S. G. Wallis and J. R. Manson
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 3, September, 131–141
The majority of approaches for predicting pollutant transport in rivers rely on being able to estimate dispersion coefficients. This paper describes four methods for doing this and argues that in most cases practicing engineers would rely on one of numerous predictive equations that have been proposed over the past 30 years or so. The paper reviews these equations and discusses some recent improvements to the theoretical representation of pertinent transport processes that implies that the latest predictors should be more reliable than older ones. Use of seven predictors for a simple test case shows considerable scatter in predictive values, indicating that predicting dispersion coefficients remains a difficult task. Interestingly, theoretically based predictors seem to give reasonably consistent, but possibly low, values while predictors that are heavily reliant on regression to observed values seem to overpredict. The paper will be of t are discharged to river systems.
Multi-stage filtration for developing world surface water treatment
B. A. Clarke, C. J. Jones, H. L. Evans, J. L. Crompton, C. C. Dorea and S. Bertrand
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 3, September, 143–149
Gravel pre-filters and slow sand filters are robust and reliable unit processes with the potential for broad small community application in the developing world as they are able to provide physical and microbiological treatment. A multi-stage system comprising gravel pre-filters, slow sand filters and terminal disinfection conforms with the multiple barrier concept in relation to pathogen removal. Employing upflow gravel prefilters as a form of pretreatment also considerably reduces the risk of the slow sand filter blocking as a result of the surface straining of particles present in the raw water. The performance of a multi-stage treatment system, comprising shallow upflow gravel pre-filters and fabric-enhanced slow sand filters, was investigated both in service and during cleaning operations in a UK-based research project. The pre-filters provided microbial and physical treatment capacity and attenuated peaks in the raw water to the benefit of the slow sand filter. The slow sand filter achieved high levels of pathogen removal in addition to providing further physical treatment. The novel raised floor configuration adopted for the upflow pre-filters enabled high cleaning efficiencies to be achieved by rapid draindown. In parallel with the research work, a multistage system was constructed at Nyabwishongwezi, Rwanda, to provide a supply for new communities settling in the northern section of the Akagera Game Park following the 1994 genocide and war. The Nyabwishongwezi Treatment Plant and Supply Network Project was promoted by the United Nations High Commissioner for Refugees, Oxfam and Minitrape, Rwanda. It was constructed broadly in keeping with the advice given to the parties promoting the project by the Centre for Environmental Health Engineering (CEHE), University of Surrey, during research visits to Rwanda in the late 1990s. In October 2003, CEHE research staff visited Nyabwishongwezi to support the Rwandan organisation (the Regie) operating the multi-stage plant and distribution system. The multi-stage system was found to be achieving substantial levels of microbial and physical improvement of the raw water obtained from the River Umuvumba.
Design guidelines for alternative formed suction inlets
D. E. Werth and D. E. Cheek
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 3, September, 151–158
Formed suction inlets are often used to improve approach flow hydraulics to large vertical turbine pumps. Current design guidelines require that the pump bell be removed and the pump modified to allow for attachment of the formed suction inlet. The present research study was aimed at developing a dimensionless design procedure for a formed suction inlet based on pump bell diameter, which does not require removal of the bell, allowing for greater flexibility and economic feasibility for use in existing pump intakes. Model studies have shown this type of inlet to be successful at alleviating adverse hydraulic phenomena, but the results and design procedures are typically private and proprietary and are not readily available in the public domain. A formed suction inlet which can be constructed outside the sump and consists primarily of flat sides has been developed. The relatively simple geometry should minimise construction costs. In addition, the inlet is designed for use under existing pumps and does not require pump removal or modification.
Modelling turbulent flow in two-stage meandering channels
P. Rameshwaran and P. S. Naden
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 3, September, 159–173
A three-dimensional (3-D) modelling study for calculating free-surface turbulent flow in two-stage meandering channels is presented. The numerical model solves the 3-D Reynolds-averaged continuity and Navier–Stokes equations with the k-ε turbulence model for steady-state flow. The flow equations are solved numerically with a general-purpose finite-volume code. The results are first evaluated against the experimental data obtained from the UK Flood Channel Facility. The predicted distributions of the free surface elevation, streamwise velocity, secondary vectors, turbulent kineti energy and bed shear stress are used to investigate the accuracy of the model prediction at both the apex and other sections along the channel. The predictive ability of the 3-D model is also assessed against results from a two-dimensional (2-D) model with regard to the distributions of free surface elevation, depth-averaged velocity and bed shear stress. The results show that the 3-D model predicts the flow fields reasonably well and estimates bed shear stress values more accurately than the 2-D model. The feasibility of applying the 3-D model to a practical field example is demonstrated for the case of an inbank flow on the River Blackwater. Here, the calculations are carried out for flow through a 130 m stretch of the River Blackwater for which detailed flow measurements were collected. The results show the ability of the 3-D model to capture the flow field with reasonable accuracy when applied to the complex boundary conditions which are needed to describe a semi-natural river. This illustrates the potential for using the 3-D model for predicting flow processes in natural rivers with complex geometry.
Performance of flood embankments in England and Wales
M. Dyer
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 4, December, 177–186
There are some 35 000 km of estuarine and river flood defence embankments in England and Wales with an annual budget of approximately £450 million spent on maintenance and new construction. The effective performance of these embankments during extreme flood events is critical for the provision of sustainable flood defences. However flood embankments can become less effective over a period of time for a number of reasons such as (a) increased frequency of flooding due to climate change, (b) an increase in the required standard of service or other functional requirements and (c) long-term deterioration from the intended condition—as constructed or maintained. The tendency for earth embankments to deteriorate with time is of particular concern because climate change and the increasing rate of occurrence of extreme events are leading to an increase in loading. This paper reviews the geotechnical factors that can affect the performance of fluvial and estuarine flood defence embankments in the short and long term. The review considers the traditional methods used to construct flood embankments compared with modern techniques, the type of local materials used for construction, the range of possible geotechnical factors that can lead to a loss of performance and finally case histories of embankment breaches.
Anaerobic treatment of sulphate-enriched wastewaters
L. H. Freese and D. C. Stuckey
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 4, December, 187–195
Anaerobic treatment is increasingly being used by industry in preference to aerobic systems to overcome more stringent legislation regarding the discharge of pollutants into the environment. As high-rate anaerobic systems such as the anaerobic baffled reactor (ABR) gain recognition as effective effluent treatment processes, greater demands are made of the systems. Previous work has shown that the ABR can achieve high carbon removal rates through biomass retention and process stability. However, limited information is available on the treatment of wastewaters containing sulphate in the ABR. As such, the aim of this work was to examine the effects of treating wastewaters with high levels of sulphate in a bench-scale ABR. Experimental work involved the use of an ABR with a 10 litre working volume and eight discrete compartments, run under mesophilic conditions (at 35°C). A baseline feed of 4 g chemical oxygen demand (COD)/l was supplemented with 0·4 g/l sulphate (a COD: sulphate ratio of 10). This allowed the development of biomass in the reactor that was accustomed to sulphate. Once the reactor was operating at a 20 h hydraulic retention time, the sulphate content of the feed was increased stepwise, resulting in a decrease in the COD:sulphate ratio to a minimum level of 1. Microbiological studies were carried out to evaluate the effect of the extreme sulphate loading conditions on the biomass. The ABR was found to perform well at low influent COD:sulphate ratios. In the front of the ABR where sulphate reduction is expected, specific sulphate reduction rates (kg SO42−/kg volatile suspended solids per day) were significantly higher than the values suggested by the literature. The results of this work showed the structure of the ABR to be well suited to the treatment of wastewaters with low COD:sulphate ratios.
Modelling of wind-induced currents in water basins
M. B. Koçyigit and R. A. Falconer
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 4, December, 197–210
This paper presents a numerical modelling study into wind-induced currents in shallow water basins. A three-dimensional, semi-implicit, finite difference numerical model is described, incorporating non-hydrostatic pressure, based on a sigma-transformed system in the vertical direction. The numerical model was first validated for sloshing in a rectangular tank; excellent agreement was obtained against analytical solutions, provided the non-hydrostatic pressure is incorporated. The model was further verified against experimental data on wind-induced circulation in shallow rectangular tanks. It was then used to simulate wind-induced, three-dimensional flow fields in idealised rectangular tanks. A parameter study was carried out for wind-induced flows in Esthwaite Water, and the predictions compared against field data. It is shown that the numerical model is capable of accurately simulating the wind-induced circulation in shallow enclosed water bodies and that the topography and wind stress are of primary importance. The non-hydrostatic pressure does not have a significant effect on the wind-induced flow fields considered herein.
A physico-chemical water treatment system for relief agencies
B. A. Clarke, J. L. Crompton and R. Luff
Proceedings of the Institution of Civil Engineers—Water Management, 157, No. 4, December, 211–216
Relief agencies that are using surface water sources to supply drinking water to displaced communities and refugees need convenient, reliable and durable treatment systems to alleviate the risk of waterborne disease. Physico-chemical unit processes with terminal disinfection can be the ‘lowest effective technology’ which satisfies rapid response and durability requirements. A physicochemical water treatment system was developed which has a minimum of power and mechanical plant requirements. The system comprised a pump driving the raw water supply through a spiral pipe flocculator and an upflow clarifier of novel new design fabricated within a standard Oxfam T11 tank. This system was intensively tested and developed in the UK in a joint Department for International Development and Oxfam-funded research and development project. It proved to be reliable and effective when treating raw water with fine colloidal turbidity, consistently providing an effluent with a turbidity of 1–2 nephelometric turbidity units (NTU) with aluminium levels well below the World Health Organisation guideline value. During the research programme an early model of the upflow clarifier was demonstrated in an International Committee of the Red Cross-sponsored Inter-Agency Technical Meeting in Geneva, where it reduced a raw water turbidity of 600 NTU to below 10 NTU, with a measured aluminium residual of only 0·041 mg/l.
