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Physical Hydraulic Model Study of Sewage Overflow Mitigation, Auckland, New Zealand

Author(s): Audsley Jones; Lena Kelly; Heide Friedrich; Bruce W. Melville

Linked Author(s): Bruce W. Melville, Heide Friedrich

Keywords: Stormwater Outfall; Hydraulic Model; Overflow Mitigation; Newmarket Gully

Abstract: The Newmarket Gully (Auckland, New Zealand) waste water outlet, designed in 1983, is prone to flooding. On average, the frequency of flooding into Newmarket stream is 102 spills per annum, with a total annual spill volume of 227,193m 3 (Watercare Services Ltd. 2007). In order to reduce this flooding and to provide additional storage capacity, Sinclair Knight Merz (SKM) proposed the addition of a storage tank on top of the existing energy dissipater and the widening of the channel downstream. The effects of those changes were tested on a scale model (1:22) in The University of Auckland’s Fluid Mechanics laboratory. The construction and testing consisted of three phases, as the design was iteratively updated based on the results of the previous phase. The initial design (Design Scenario 1) posed problems with a jet forming from the 1200φ pipe. The precast design (Design Scenario 2) featured a modified 1200φ inlet so that the flow was streamlined along the system and the velocity reduced, however issues arose further downstream as the system pressurised. The final design (Design Scenario 3) increased the volume of the system so that for the maximum tested flow rate (41m 3 /s) pressurisation did not occur.


Year: 2010

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