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In the following example the upper panel simulates daily rainfall over a one year period, and the below pictures display the flooding effects on the 49 sub-basins in the Manawatū Catchment.
The left hand side of the video below: shows the percentage in flooded area per sub basin when no man-made flood protection (stop banks, levees, dikes) is present. The model to-date does not include existing man-made flood protection which prevents predicted flooding in the red zone. This will be added in. Also rainfall which is currently a simulated time series will be replaced by measured data.
The right hand side of the video below: shows the need for flood protection (0, red, is where flood protection is not provided but needed) versus no need for flood protection (1, grey, where flood protection is provided naturally or is not needed). Natural flood protection occurs where slopes in the sub basin are too steep for standing water, or when not enough water accumulates to cause flooding. Flood protection is not needed when the floods are in areas where they do not cause damage to human quality of life (wetlands, forests and riparian zones).
The model does not separate out flooding in pastures or crop areas from flooding in urban areas. Therefore, the need for flood protection is as important for agricultural areas as for urban areas. Decision-makers have the option to allow some flooding in agricultural areas to reduce the need in flood protection. This can be built into the model but it is hard to get information on where this is best done.
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Last updated on Tuesday 16 August 2016