Flood Assessment Projects

Patea Dam, Taranaki

PateaFlood 400
A review was undertaken of the June 2015 flood event at Patea Dam - the largest flood on record at the dam since its commission in 1984.  The scope of the review included a rainfall frequency analysis; a flood frequency analysis; and a review of the adequacy of the catchment model using observed data during the event.  The dam has a catchment of approximately 870km2 and a 1% AEP flow of 1,080m3/s.

Water Bottling Factory, Nananu, Fiji

WaterBottlingFiji 400
Flood assessment for a new water bottling factory adjacent to the Yaqara River, on the northern side of Viti Levu, Fiji.  The Yaqara was determined to have a catchment area of 35 square kilometres. A HEC-RAS model was developed to predict the 1% AEP flood levels within the Yaqara and an adjacent tributary. The model results were used to set the minimum floor levels for the development and minimum bridge levels required to access the site. The factory access road will cross over the Yaqara on a bridge where the 1% AEP flow was predicted at 525m3/s.

Residential Subdivision, Riverhead, Auckland

DukeStFloodAssess 400
A flood assessment was undertaken for a proposed 19-lot residential subdivision for land located near the Wautaiti Stream, within a 1% AEP floodplain. A HEC-HMS model was developed to determine a 1% AEP flow of approximately 77m3/s. Hydraulic modelling was then undertaken using DHI MIKE 11, a one-dimensional software package for open channel flow. Results of analysing pre- and post-development flood levels indicated a negligible increase in 1% AEP flood levels on adjacent properties upstream or downstream of the property as a result of the proposed development. A 15m wide box culvert system was designed to operate during significant flood events should stream banks overtop upstream.

Albert Park, Suva, Fiji

AlbertPark 400
Commissioned by Suva City Council to undertake the civil design of stormwater and earthworks levels for the redevelopment of Albert Park. New stormwater reticulation was designed to improve stormwater drainage from the park to accommodate flows from a 5% AEP event.


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