New Arterial Road Flood Assessment

Client:  Waimakariri District Council
Date:  2015 – 2016

Waimakariri District Council engaged us as part of their evaluation to construct a new arterial road west of Kaiapoi, Canterbury.  The proposed arterial route road involved the construction of a new stretch of road extending from Ohoka Road near State Highway 1 to meet Butchers Road in the west, and the upgrade of Butchers Road north to Island Road near the existing Ohoka Stream Bridge.  In addition to providing important infrastructure for the Silverstream Estates residential development, the arterial route road is expected to provide an important link between Kaiapoi and Rangiora.

We were engaged to undertake hydrological and hydraulic analysis of the proposed road.  In particular, the assessment focused on determining potential increases in flood levels caused by the proposed road.

We were previously commissioned to carry out a comprehensive 2-dimensional flood modelling analysis for the nearby Silverstream Estates residential development.  This model was extended to include the proposed road alignment and profile.  The model showed that for the design events analysed, the proposed road caused a decrease in flood levels to the east of the site near State Highway 1 and an increase in flood levels to the west of Butchers Road.  The increase in flood levels was found to occur only on rural land and to not cause additional flooding of residences. In addition to assessing the new road alignment, various structures including culverts and two bridges were analysed.

Following the hydrological and hydraulic analysis, we were subsequently engaged to prepare the necessary resource consent applications and Assessment of Environmental Effects for the construction of the new road.


Key Aspects:

  • Hydrological analysis
  • 2-D hydraulic modelling of new road and surrounding area
  • Resource consenting

Client:  Waimakariri District Council
Date:  2015 – 2016



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