Rainfall Reporting: Past, Present, Future?

Auckland Council has a comprehensive rainfall and flow gauge network, yet core data needed to run and understand our business was difficult to access and, available to only a handful of technical staff. Post event analysis of rainfall data was taking 24 hours or longer, depending on the outputs required.

Only a historical understanding of an event could be gained, due to the time required to analyse data, and limited access to the data. Council recognised the need to make data accessible to 120+ staff, and to allow reporting within minutes of rainfall occurring – and preferably to provide a forecast – to assist in event management, and preferably to give advance warning of the potential for heavy rain.

We recognised if proprietary rainfall data could be made visible via the cloud, to a wide range of people, in an intuitive GIS based environment we could better fulfil our function as a Stormwater Utility. We directly tackled this issue, and all rainfall data is now available via a web based geospatial portal, which puts the first piece of the puzzle in place.

The geospatial portal has now been extended to allow regional post event reporting, almost in real time, showing rasters, and contours for ARI across different durations across the region – post event reporting now takes a fraction of the time it took prior.

There is a need however to improve reporting, beyond the capabilities of our current point gauge network. The spatial density of rain gauges means either the most intense rainfall may be missed, or spatially overrepresented by a gauge – either way, significant bias is introduced in spatial extrapolation from point gauges.

Council have now successfully implemented Metservice rain radar via the same web portal as the gauge data.