DEVELOPING THE CONCEPT OF AN ACTIVE FLOOD RISK MANAGEMENT SYSTEM IN CHRISTCHURCH

The Dudley Creek catchment in Christchurch has a long history of flooding, a risk which has been increased in many locations by the 2010/11 earthquake series. The catchment is drained by a complex network of waterways and pump stations, and includes the significant Cranford Basin rural area which has long been proposed as a strategic flood storage area. The location of Cranford Basin and shallow topography are such that some of the waterways have the potential to drain to either the Styx or Avon Rivers, or could be controlled to do so.

Jacobs has been working with Christchurch City Council to develop a strategic plan for actively managing the system of drains, pump stations and storage basins to assist in the mitigation of flooding in the Dudley catchment. Through workshops with key staff and modelling, the project has taken time to understand the complex interaction and function of the whole system in substantial detail. This detailed understanding has led to a robust conceptual understanding of the whole land drainage network which in turn has enabled an improved management plan to be developed.

A key feature of this improved concept is to actively manage the various components of the network during a flood event. This proposes installing a network of level monitors around control gates and installing remote communication technology so that control gate and pump station operations can be coordinated. Importantly, failsafe asset operation can be set in the event of communication breakdown during a storm. The logic for actively managing the network is to ensure storage basins are utilised optimally in order to reduce the flood risk to the community while minimising human intervention.

This paper describes the benefits of the process undertaken to develop the active management concept, as well as the key components of the proposed concept design.