Horizons Regional Council – flood forecasting

Client: Horizons Regional Council
Location: Palmerston North, New Zealand
Date: 2009

Developing a flood forecasting system to provide timely and accurate flood warnings for better preparation, greater public safety and reduced damage and costs


Horizons Regional Council covers a large area of the North Island of New Zealand. The major rivers within the area pose a flood risk to rural and urban areas, and flood warning was required to manage this risk to life, infrastructure, property and the environment.


The Horizons Regional Council engaged Entura to develop a computerised flood forecasting system incorporating most of its major rivers.  The system comprises continuous rainfall-runoff-routing models that input real-time and forecast information, and produce forecast flows up to 48 hours into the future.

In urban areas the forecast hydrographs are input to hydraulic models to obtain forecast flood levels for floodprone and populated regions. The flood levels and flows are linked to a web-based inundation mapping tool that provides up-to-date forecasts of potential inundation.

The entire system is automated and integrates with the Council’s existing database and web-based interfaces. An ongoing support program and staff training ensure knowledge transfer and continuous improvement of the modelling system.

Entura was responsible for the hydrologic and hydraulic modelling, and development of a user interface and flood inundation mapping tool for the project. This involved high levels of expertise in developing and calibrating hydrologic and hydraulic models, programming, and web-based interface development.


The simple web-based user interface allows operators to visualise the potential extent of the forecast flood via a map showing inundated areas. The integrated system allows the Council to provide timely and accurate flood warnings, with projections of potential areas of inundation, enabling early and accurate flood warnings for better management of flood risks.