2016 – Paradise Dam – An Analysis of Severe Damage to a Modern Dam

David Scriven, Lawrence Fahey

Paradise Dam is located approximately 20 km north-west of Biggenden and 80 km south-west of Bundaberg on the Burnett River in Queensland. The dam was designed and constructed under an alliance agreement with construction completed in mid 2005. It is a concrete gravity structure up to 52 m high, the primary construction material being roller compacted concrete (RCC).

In January 2013 the flood of record was experienced at the dam with a depth of overflow on the primary spillway reaching 8.65 m following heavy rainfall in the catchment from ex-tropical cyclone Oswald. The peak outflow was approximately 17,000 m3/s. This equated to a 1 in 170 AEP flood event. When the flood receded it was discovered that the dam and surrounds had suffered severe damage in a number of locations including: extensive rock scour downstream of the primary dissipator and the left abutment, damage to portions of the primary dissipator apron, and the loss of most of the primary dissipator end sill.

SunWater initiated a staged remediation program to manage the dam safety risks and by November 2013 had completed the initial Phase 1 Emergency and Phase 2 Interim repairs. Phase 3 of the program was to implement a comprehensive Dam Safety Review (DSR) and a Comprehensive Risk Assessment (CRA). The DSR became arguably the largest ever undertaken by SunWater and included: extensive geotechnical investigations, large scale physical modelling, numerical scour analysis, stability analysis, and an extensive design assessment. This paper describes some of the key aspects of the DSR undertaken related to the flood damage.