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.
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A strategy designed to ensure that an existing dam continues to perform effectively will include:
This paper will explore each of these issues and how they may be applied to dams in a variety of situations. These situations include water supply reservoirs, flood retarding basins, levees and wastewater lagoons. While each situation is different, the underlying principles will remain consistent. The range of situations encountered by Victorian Water Authorities provides the inspiration for the development of an efficient approach to the management of the safety of dams.
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.
ANCOLD Environmental Guidelines have been under preparation for a considerable time. A brief for their preparation followed a resolution by the ANCOLD executive in 1991] that:
“ANCOLD should be seen by the profession and the community as a credible and informed source of information on the risks and benefits associated with dam projects.”
Why the guidelines were initiated, why they have taken the time they have to prepare and what they cover are described in this paper.
To the author’s knowledge, they are the only guidelines of their type, addressing the environmental effects of dams and associated works. It is hoped that they generate substantive debate. This paper initiates the public comments phase.
The paper has two purposes:
° = To introduce the guidelines ° To use the guidelines to introduce this environmental issues session of this conference
Shane McGrath and Michelle Cowan
Goulburn-Murray Water (G-MW) is a Victorian rural water authority with responsibility for management of the major water systems within a 68,000 square kilometre region. Following a detailed business risk assessment undertaken in 1996, Goulburn-Murray Water developed a ten-year program to commence design reviews and address identified deficiencies at thirteen dams for which G-MW has responsibility.
In October 1997, the Victorian Government announced a $450 million regional water reform package, of which $35 million was provided for rural water authorities dam improvements. $18.5 million was allocated to G-MW on a ‘dollar for dollar’ basis. With contributions from G-MW customers, the current total funding amounts to $37 million.
This paper focuses on processes that G-MW has adopted to manage an accelerated program of dam design review and remedial work.
Ungated spillways offer the safest form of spillway but they are more costly than gated spillways for the volume of water stored. Gated spillways offer a more cost-effective use of water by maximizing the storage capabilities of the dam. Gated spillways also lead to more cost effective new dams as well as increasing storage of existing dams. They can therefore offer considerable advantages but must not jeopardize dam safety. Most commonly used spillway gates are mechanically driven by electric or hydraulic systems reliant on external power supply and instrumentation, and usually require operators to control the systems. Unfortunately there is already a substantial record of these types of gates not operating when required, thereby placing the dam’s safety in jeopardy. The ideal is to have automatic gates which do not suffer the problems associated with mechanically-driven gates.
A number of automatic gates exist, some with differing degrees of success but most are not truly automatic in operation and suffer some limitations. A range of fully automatic water control equipment has been developed and has operated for more than 20 years in South Africa. Out of experience gained from this equipment, a new generation of spillway gates has been developed which meets nearly all the requirements of an ideal spillway gate.
This paper introduces the gates and examines their features and safety devices. Other benefits are also mentioned.