Numerical investigation into the stability of earth dam slopes considering the effects of cavities

This research is an attempt to estimate the influence of the presence of cavities on the stability of slopes in earth dams under rapid drawdown conditions. The aim of the investigation is to study the influence of different factors, such as the diameter and location of cavities. A series of finite element simulations was conducted using PLAXIS 2D to develop models and analyse slope stability in earth dams while considering the effect of cavities in the subsoil. The combined effects of cavities and the strength parameters of slopes on the stability were also investigated and parametrically analysed. The results indicated that presence of cavities and an increase in the diameter of cavities decreased the stability of the upstream face dramatically for all examined locations in a horizontal direction; however, this effect was less on the downstream side. The results also showed that variations in the location of cavities in the horizontal direction have a greater effect on the stability compared to the vertical direction. The results revealed that increasing shear strength parameters of embankment do not reduce the influence of cavities on stability when those cavities are in critical locations

Impact of soil and water conservation measuren on catchment hydrological response: a case in north Ethiopia

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post-harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre-implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5mm(RCD 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002-2003 (ΔT/WS D 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. © 2010 John Wiley & Sons, Ltd

Modelling to bridge many boundaries: the Colorado and Murray-Darling River basins

Increasing pressure on shared water resources has often been a driver for the development and utilisation of water resource models (WRMs) to inform planning and management decisions. With an increasing emphasis on regional decision-making among competing actors as opposed to top-down and authoritative directives, the need for integrated knowledge and water diplomacy efforts across federal and international rivers provides a test bed for the ability of WRMs to operate within complex historical, social, environmental, institutional and political contexts. This paper draws on theories of sustainability science to examine the role of WRMs to inform transboundary water resource governance in large river basins. We survey designers and users of WRMs in the Colorado River Basin in North America and the Murray-Darling Basin in southeastern Australia. Water governance in such federal rivers challenges inter-governmental and multi-level coordination and we explore these dynamics through the application of WRMs. The development pathways of WRMs are found to influence their uptake and acceptance as decision support tools. Furthermore, we find evidence that WRMs are used as boundary objects and perform the functions of ‘boundary work’ between scientists, decision-makers and stakeholders in the midst of regional environmental changes

Derivation and verification of empirical catchment response time equations for medium to large catchments in South Africa

Published ArticleDespite uncertainties and errors in measurement, observed peak discharges are the best estimate of the true peak discharge from a catchment. However, in ungauged catchments, the catchment response time is a fundamental input to all methods of estimating peak discharges; hence, errors in estimated catchment response time directly impact on estimated peak discharges. In South Africa, this is particularly the case in ungauged medium to large catchments where practitioners are limited to use empirical methods that were calibrated on small catchments not located in South Africa. The time to peak (TP), time of concentration (TC) and lag time (TL) are internationally the most frequently used catchment response time parameters and are normally estimated using either hydraulic or empirical methods. Almost 95% of all the time parameter estimation methods developed internationally are empirically based. This paper presents the derivation and verification of empirical TP equations in a pilot scale study using 74 catchments located in four climatologically different regions of South Africa, with catchment areas ranging from 20 km2 to 35 000 km2. The objective is to develop unique relationships between observed TP values and key climatological and geomorphological catchment predictor variables in order to estimate catchment TP values at ungauged catchments. The results show that the derived empirical TP equation(s) meet the requirement of consistency and ease of application. Independent verification tests confirmed the consistency, while the statistically significant independent predictor variables included in the regressions provide a good estimation of catchment response times and are also easy to determine by practitioners when required for future applications in ungauged catchments. It is recommended that the methodology used in this study should be expanded to other catchments to enable the development of a regional approach to improve estimation of time parameters on a national-scale. However, such a national-scale application would not only increase the confidence in using the suggested methodology and equation(s) in South Africa, but also highlights that a similar approach could be adopted internationally

Chalk-steel Interface testing for marine energy foundations

The Energy Technology Partnership (ETP) and Lloyd’s Register EMEA are gratefully acknowledged for the funding of this project. The authors would also like to acknowledge the support of the European Regional Development Fund (ERDF) SMART Centre at the University of Dundee that allowed purchase of the equipment used during this study. The views expressed are those of the authors alone, and do not necessarily represent the views of their respective companies or employing organizations.Peer reviewedPostprin

Overcoming failure in infrastructure risk governance implementation: large dams journey

[EN] There is ample recognition of the risk inherent in our very existence and modes of social organization, with a reasonable expectation that implementing risk governance will result in enhanced resilience as a society. Despite this, risk governance is not a mainstream approach in the infrastructure sector, regardless of the increasing number of peer-reviewed published conceptualizations, mature procedures to support its application, or public calls to cope with systemic risks in our modern societies. This paper aims to offer a different view on the issue of risk governance, with focus in the analysis of the root causes of its relatively low degree of implementation in the infrastructure sector. We later analyze the impact of such essential causes, which we have grouped and labeled as the ontology, the concerns, the anathemas, and the forgotten, in the specific field of large dams. Finally, we describe the journey toward risk governance in the specific field of large dams, thus supporting the ultimate objective of this paper to facilitate an evidence-based approach to successful risk governance implementation within and outside the dam sector.This work was supported by Spanish Ministry of Economy and Competitiveness (Ministerio de Economía y Competitividad (España) [grant number BIA2013-48157-C2-1-R].Escuder Bueno, I.; Halpin, E. (2016). Overcoming failure in infrastructure risk governance implementation: large dams journey. Journal of Risk Research. https://doi.org/10.1080/13669877.2016.1215345SAbrahamsen, E. B., & Aven, T. (2012). Why risk acceptance criteria need to be defined by the authorities and not the industry? Reliability Engineering & System Safety, 105, 47-50. doi:10.1016/j.ress.2011.11.004Ardiles, L. D. Sanz, P. Moreno, E. Jenaro, J. Fleitz, and I. 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Bulletin of the Atomic Scientists, 68(2), 9-21. doi:10.1177/0096340212440359Hartford, D. N. D., & Baecher, G. B. (2004). Risk and uncertainty in dam safety. doi:10.1680/rauids.32705IRGC (International Risk Governance Council) 2005.Risk Governance: Towards an Integrative Approach, White Paper No. 1, O. Renn with an Annex by P. Graham. Geneva: International Risk Governance Council.Krause, P., Fox, J., Judson, P., & Patel, M. (1998). Qualitative risk assessment fulfils a need. Lecture Notes in Computer Science, 138-156. doi:10.1007/3-540-49426-x_7Kröger, W. (2008). Critical infrastructures at risk: A need for a new conceptual approach and extended analytical tools. Reliability Engineering & System Safety, 93(12), 1781-1787. doi:10.1016/j.ress.2008.03.005Lofstedt, R. E. (2010). Risk communication guidelines for Europe: a modest proposition. Journal of Risk Research, 13(1), 87-109. doi:10.1080/13669870903126176(2008). 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Developments and criticisms of risk analysis and precautionary reasoning. Journal of Risk Research, 13(4), 517-543. doi:10.1080/13669871003629887Zhao, X., Hwang, B.-G., & Low, S. P. (2015). Enterprise Risk Management in International Construction Operations. doi:10.1007/978-981-287-549-