Dr Andy Hughes , Tom Wanner , Ben Jones
This paper will present the ideas formulated to safely pass the design floods for ten dams within this sensitive environment, which include the installation of new spillways and/or the raising of dam crests, whilst taking in to account the site constraints and the age of the dams, some of which are up to 300 years old. The risk assessment carried out to quantify the overall risk of the dam failures will also be discussed including the breach inundation flood modelling of central London.
The paper will focus on the engineering and environmental constraints of the project in relation to the highly urbanised area, and the challenges faced when trying to accommodate the needs of many government and high profile stakeholder bodies, and pieces of legislation, in one of the most politically sensitive parts of the country.
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Now showing 1-12 of 39 2978:
Phillip Jordan, Alan Seed, Rory Nathan, Peter Hill, Eva Kordomenidi, Clive Pierce, Michael Leonard
This paper discusses the stochastic framework that was used to generate the 5449 sets of inflow hydrographs, to develop and stress test a dam operations model. The stochastic simulations were driven by 600 different space-time patterns of rainfall generated using a stochastic space-time multiplicative cascade model. Eight significant storms were identified in the radar archive to identify parameter sets for the stochastic generation algorithm and 600 replicates of space-time rainfall were generated. The statistical properties of spatial patterns of 48-hour rainfall bursts on eight major subcatchments of the Brisbane River catchment from the 600 stochastic replicates were verified against the same statistics derived from 38 major flood causing rainfall events observed in the catchment. The hydrographs were generated using an URBS rainfall runoff routing model of the Brisbane River catchment, which was calibrated to 38 historical flood events (between 1955 and 2013) and tested on a further 10 historical flood events (between 1887 and 1947).
The stochastically simulated sets of inflow hydrographs were then used to assess the impact of variations in flood operation rules for Wivenhoe and Somerset dams. The stochastically generated events exhibit substantial variability in runoff hydrographs but with variability that is statistically consistent with observed events. The stochastically generated hydrographs provide a considerably more realistic basis for testing the outcomes for different flood operations strategies than the single design event approaches that have previously been adopted.
Peter Hill, David Stephens, Kelly Maslin, Rachel Brown, Simon Lang, and Chriselyn Meneses
There has been a growing awareness of the potential dam safety risks associated with hydraulic structures in urban environments such as retarding basins, water quality detention basins and recreational lakes. This has required estimates of rare and extreme floods for urban catchments and there are a number of important characteristics of urban catchments which distinguish them from rural catchments such as impervious areas, lack of streamflow data, blockage of structures and complex hydraulics. This paper describes the key considerations for flood estimation in urban catchments and draws examples from a number of current flood studies for urban catchments in Canberra.
Peter F Foster and Peter K Silvester
Clyde Dam, the largest concrete gravity dam in New Zealand, was constructed in the 1980’s on the Clutha River in New Zealand. Lake Dunstan, which is the reservoir formed by the dam, reached its full operating level in 1993, some 21 years ago.
This paper summarises the performance of the dam over this period, the changes in operations that have been undertaken and looks to future challenges. The performance and management of the landslides around Lake Dunstan that were remediated prior to lake filling is outlined. The large floods experienced in the Clutha River in the 1990’s highlighted aspects of the flood management procedures that needed amending to capture lessons learned and some modifications to appurtenant structures have been completed. Changes to the environmental management in moving from water rights to consent conditions under the Resource Management Act are addressed.
Over the last 21 years a sediment delta has progressed down Lake Dunstan, as expected, and a long term sediment management plan has been developed for both Lake Dunstan and Lake Roxburgh which is downstream of Clyde Dam. A summary of the plan is discussed. The seismic hazard at the dam site is currently under study to update the seismic assessment parameters for the dam.
Guresh Ahuja, Brian Cooper, Olaf Rutgrink and Andrew Thomson
This paper presents details of the State Water Corporation of NSW Australian first temperature control curtain project aimed at dealing with the environmental issue of cold water pollution in dam offtakes. This is a key project focused on dealing with a known environmental issue and reflects changing environmental and social expectations for dam operators. In the concept phases this project was part of the NSW Rivers Environmental Restoration Program (RERP) sub-program ‘better delivery of environmental water’.
The paper presents the development of the design concept including early concept screening and selection, scale model testing, concept design development, hydrodynamic, structural and computational fluid dynamic analyses leading to the final design that has now being constructed. The concept design work was completed in 2011 and following a tender process a design and construct contract was let for the detailed design and construction of the temperature control curtain system. This phase of the work was recently completed and the temperature control curtain is now fully operational. The actual performance and effectiveness of the temperature control curtain will only become evident after a few years of operation and will also hinge on the degree of stratification in the dam.
Przemyslaw A. Zielinski
Three aspects of the current engineering practice in using event trees in dam safety risk analyses are discussed in the paper. These aspects include assignment of probabilities for initiating events, treat-ment of dependencies in the event tree, and dynamic aspects of dam system behaviour and accounting for time. The paper discusses limitations of the methodology and common mistakes in engineering applications of event tree methods when assessing dam safety risks and making safety decisions for specific dams. Of particular importance is the discussion of incorrect interpretation of dependency structure when addressing common cause failure modes.