Michael Cawood, Roger Jones and Ken Durham
A methodology for local disaster management planning based on Australian/New Zealand Standard AS/NZS 4360:1995 — Risk Management has been developed as an out-working of a Flood Risk Study for Murweh Shire. The methodology has relevance to all local governments, particularly in view of National Disaster Relief Arrangements (NDRA) that now link the extent of NDRA funding available for a re-occurring natural disaster event to the existence of disaster mitigation actions or plans. This places a premium on actions being taken by local governments to mitigate public safety risk at community level.
Peter Allen, Don Cock, Garry Grant and John Ruffini
The paper examines the performance of the Brisbane River and Pine River real time flood management system for the operation of Somerset Dam, Wivenhoe Dam and North Pine Dam during the 1999 flood event.
The February flood event, which was about 80% of the magnitude of the disastrous 1974 flood event upstream of Wivenhoe Dam, was the first major flood event to be managed by the system and it performed very creditably. The overall flood management system comprises:-
A network of 125 ALERT type rainfall and river height stations throughout the catchment; A data management system to facilitate data collection and data validation;
The paper describes the system and gives details of the performance of the system during the February event. It details the performance of the dams during the event and how this was optimised to maximise the safety of the dams and minimise impacts on those downstream.
Gary Hargraves, Russ McConnell and John Ruffini
The acceptance of the use of generalised methods for estimating extreme rainfall has resulted in a growth of the Probable Maximum Flood (PMF) estimates that spillways of dams are required to pass. In many cases spillways were not designed with spare capacity and are incapable of safely passing the new PMF estimates. Dealing effectively with the potential for dams to cause damage and loss requires a risk management approach. Such an approach requires more reliable tools for estimation of rainfall. This paper examines the issues, the progress made, and outlines further work and options for clarifying risk.
Kumara Arachchi and Kelvin J Lambkin
Wetlands by their very nature act as storages of pollutants and nutrients in systems subject to environmental stresses. Wingecarribee Swamp acted in this manner and enhanced the quality of catchment runoff flowing into the Wingecarribee Reservoir until the structural failure of early August 1998 in which 6000 megalitres of peat and sedimentary material were moved into the Reservoir. Protection of the Swamp’s functions and values is directly related to Sydney Catchment Authority’s core objectives of protecting the environment and protecting public health by supplying drinking water of acceptable quality. Due to the catastrophic failure, water quality in the reservoir and the ecological integrity of the Swamp have been compromised. The incident has also resulted in significant dam safety issues.
This paper describes the dam safety, catchment management and water quality response to the failure of a major peatland which covered 8% of the catchment of Wingecarribee Reservoir in the Southern Highlands of New South Wales.
Brian Haisman, Clarke Ballard and Neville Garland
In early 1997 the Murray-Darling Basin Ministerial Council instigated a review of the operations of its primary reservoirs, the Hume and Dartmouth Dams, in response to concerns of floodplain communities below the dams, coupled with changing community values in relation to the in-stream environmental effects of dams. The review, completed in May 1999, achieved a consensus between parties advocating what are on the surface irreconcilable objectives for the management of the water resource. Foremost competing objectives were flood mitigation, consumptive water use, and environmental health of the river system, plus subsidiary objectives related to recreation, hydro-electric generation, salinity management, tourism and the like. The keys to success were firstly, creation of a community-based Reference Panel which took on a steering role coupled with extensive consultation, and secondly a determination to describe situations wherever possible by means of factual information. The paper describes the identification and evaluation of issues, the consensus building process, the intensive hydrology and economic modelling undertaken, and the development of a comprehensive set of flow parameters which could be viewed as surrogates for environmental outcomes. Conclusions and recommendations are drawn for future reviews of similar dams.
Dr. Azam Khan and Dr. Anil Patnaik
Concrete dams are thinner than embankment dams and impose more concentrated loads on the foundation and abutments. A narrow valley with sufficient rock foundation is a typical site for concrete dam, which require a solid foundation that is relatively free of faults, shears, and major changes in foundation strength. Such discontinuities can overstress the concrete by causing some areas of dams to carry more loads than other areas. The measurement of deflections and use of finite element technique can predict the stresses in the concrete dams. A computer model is underdeveloped for prediction of deflections and stresses in Concrete Dam by using finite element. At the first stage of this study, measured deflections from Burrinjuck Dam are compared with the predicted deflections by using finite element. This paper outlines the deflections measured in the dam due to temperature variations and comparison of the measured thermal deflections with those predicted from a finite element analysis.