M. Tooley, D. D’Angelo, B. Priggen, K. Sih, N. Vitharana, R. Mouveri
As the urban sprawl of residential and commercial businesses expand to meet rising population, consideration must be given to the frequency and intensity of storm events and changes in tidal levels, to mitigate the risk of flooding and damage associated with the failure of hydraulic structures.
This paper outlines the design method undertaken to ensure the ageing structure (founded on timber piles) meets modern dam safety criteria, extends the life of the 8 gates operating mechanisms and provides overall inherent reliability for the whole structure. The design method included updated hydrological assessment of the upstream catchment, geotechnical investigation, liquefaction review, consequence category and AFC assessment, hydraulic assessment and stability analysis.
These assessments are being undertaken to introduce inherent reliability in their operation in particular during king tide or storm water events, or a combination of the both, minimising leakage and breakdowns and ensuring the risks of flooding to low lying residential areas upstream of the structure and major airport are minimised. The Glenelg Gates structure is an integral part of a larger regulating system for the catchment.
The findings of the design upgrade would be useful to dam designers and owners faced with the upgrading of gated structures with flooding risks in residential areas.
Keywords: Gated Glenelg Gates structures, upgrade, dam design guidelines.
Now showing 1-12 of 40 2976:
Zhenhe Song, Arjuna Dissanayake, Shunqin Luo
One of the potential tailing dam failure modes that is commonly evaluated is for prediction of earthquake induced crest displacement in relation to available freeboard. The prediction of seismic induced displacement for tailing dams can be evaluated using simplified approaches, i.e. analytical methods by Newmark (1965), Makdisi and Seed (1978), Bray and Travasarou (2007) and empirical method by Swaisgood (2003) and Pells and Fell (2003).
Seismic induced displacements have been estimated using these simplified methods and numerical methods by FLAC and PLAXIS. The results from the numerical modelling were compared with results derived from the simpler analytical and empirical methods. The results indicate the numerical analysis results agrees reasonably well with empirical methods by Swaisgood (2003) and Pells and Fell (2003) and can be used to provide additional confidence in the seismic stability of tailings embankments. However, simplified analytical methods by Newmark (1965), Makdisi and Seed (1978), Bray and Travasarou (2007) could underestimate the seismic induced displacements.
Keywords: Tailing dam, Seismic analysis, numerical analysis, simplified analysis, liquefaction.
P C Styles, A L Garrard
The Victorian town of Nathalia was surrounded by flood water during the March 2012 floods in Northern Victoria.
Nathalia is protected by earthen levees of various sizes and age. Portable aluminium levees were installed during the March 2012 flood event, generally in areas where a permanent levee would restrict access to a park and views. The flood level came within 200mm of the crest of many of the levees and remained at a high level for nearly 2 weeks.
The paper describes the emergency management issues and procedures which relied on engineering advice to provide targeted and relevant remedial works on the levee system as potential problems arose. Engineers worked alongside the SES, CFA, Victoria Police, ADF and other volunteers to monitor, repair and reinforce the levee system on a 24 hour basis. The engineering support continued over a period of approximately 2 weeks, from the time the flood waters commenced rising until they had receded sufficiently for the orders for evacuation of the town to be rescinded.
Keywords: Nathalia, floods, levees, emergency management
A.E. Bentley, P.I. Hill, S.M. Lang, M. Freund, A. Richardson
This paper describes the development of a detailed assessment approach using spatial data to estimate the consequences of dam failure across a portfolio of 18 dams in NSW. The assessment is made for potential loss of life; economic and financial losses and a qualitative assessment of environmental and social impacts. The approach is designed around the use and interrogation of spatial databases combined with outputs from hydraulic models. The assessment method is applicable to a wide range of dams in different valleys, each with different downstream characteristics. The paper provides discussion on the advantages of the approach and presents some insights into the effective application to a dam portfolio of significant size and scale.
Keywords: consequence assessment, spatial databases
John Grimston, David Leong, Robin Dawson
The Angat Multipurpose Project, originally constructed in the 1960’s, is located 60 km north-east of Manila, and provides power, irrigation and domestic water supply and flood mitigation. The major water-retaining structures of the scheme are a 131 m high main rockfill dam and a 55 m high rockfill saddle dam.
Previous seismology studies have identified the presence of a possible branch of the West Valley Fault crossing under the saddle dam. If the fault dislocated, the branch under the saddle dam could produce horizontal and vertical shear displacements. Further, earthquake shaking poses a risk outside the fault zone. If the main dam/saddle dam were to fail in such an event, there would be major consequences in respect to both the water supply (serves a population of approximately 10 million) and the large population living below the dams. The dams are thus in the highest hazard category under any internationally accepted standard.
A study to investigate the dam safety aspects and identify remediation works which would bring the seismic performance of the main dam/saddle dam system up to an acceptable level was undertaken and included:
The main conclusions were:
Keywords: Dam, Remedial, Seismic, Fault, Spillway.
Kelly Maslin, Mark Foster, Len McDonald
A key requirement of assessing the tolerability of dam safety risks is the assessment of individual risk. The ANCOLD Guidelines on Risk Assessment provides guidance on acceptable levels of individual risk and some general guidance on the calculation of individual risk.
Individual risk is a key measure in the consideration of the tolerability of risk, ALARP and development of risk mitigation works. It is essential that there is consistency in the approach to estimating individual risk used across the dams industry.
This paper reviews the approaches taken to estimating individual risk across the dams industry both locally and internationally as well as the experience of other industries.
The paper includes a review of the various methods for estimating the vulnerability of individuals subjected to flood inundation based on historical fatality rates as well as identification of the individual most at risk
The paper then describes a method that has been developed based on the principles used for assessing individual risk due to other hazards, such as landslides. The method includes consideration of a range of factors such as warning time, temporal variation and vulnerability of the individuals most at risk. The method developed provides a transparent, defensible and pragmatic approach to estimating individual risk. Practical guidance and examples are also provided on the application of the method.
Keywords: individual, risk, exposure, fatality