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Flood prone areas (FPA) are potential ponding areas that have no natural outlet and may flood frequently.
FPA are topographical depressions. The areas occur naturally or are created by dammed gullies created by man-made features such as roads and railway embankments. The flood prone extent is the area water will pond up to in a 1% AEP extreme rainfall event (Maximum Probable Development (MPD) and climate change scenario) assuming the outlet to the topographical depression is blocked. All FPA were generated based on an existing development (ED) situation. The layer was created by WSP and is managed by the Healthy Waters Regional Planning team. It was updated in June 2021 and is an update of an existing layer that was created in 2013.
The FPA layer was generated from Auckland Council’s latest LiDAR data, which was flown in 2016 and became available after processing in 2018. The 2016 LiDAR data had a much higher point density (4 points per m2) than previous versions, resulting in more spatially accurate flood prone areas.
FPA will be updated on an ad hoc basis to align with updates to Auckland Council’s LiDAR data.
Vertical Datum: NZVD1946
A summary of the fields and their definitions is as follows:
Field | Description |
CatchmentArea / Catchment Area (m2) | Catchment area upstream of the flood prone area. |
DepID / Depression ID | Depression ID |
Depth100y / 100yr ARI Future Scenario ponding depth (m) | Maximum water depth in the 100yr ARI Future Scenario rainfall event assuming the outlet is totally blocked. |
MaxDepth / Max ponding depth (m) | Maximum ponding depth in the flood prone area (spill elevation minus minimum elevation). |
MinimumLevel / Minimum elevation of depression (m RL) | Minimum elevation in the flood prone area. |
RainfallExisting / 100yr ARI Existing Scenario rainfall (mm) | TP108 24hr 100yr ARI Existing Scenario rainfall depth (effective depth over entire catchment). |
RainfallFuture / 100yr ARI Future Scenario rainfall (mm) | TP108 24hr 100yr ARI Future Scenario rainfall depth (existing rainfall depth multiplied by 16.8% to account for a 2.1-degree Celsius temperature rise due to climate change). |
RainfallRequired / Rainfall required to fill (mm) | Rainfall required in the catchment to fill up the depression to the spill elevation. |
SpillElevation / Spill elevation (m RL) | Spill elevation (m RL) |
Vol100yrm3 / 100yr ARI Future Scenario volume (m3) | Volume stored in a 100yr ARI Future Scenario rainfall event assuming the outlet is totally blocked. |
VolumeM3 / Volume to spill elevation (m3) | Max. volume that can be stored in the flood prone area. |
Dam / Dam | Identifies if flood prone area is classed as a large dam. |
DamClass / Dam classification | Identifies the classification of the dam (classifiable or referable) |
Level100y / 100yr ARI Future Scenario flood level (m) | The level water will pond up to in a 100yr ARI Future Scenario rainfall event assuming the outlet is totally blocked. |
CanFill / Can fill in a 100yr ARI Future Scenario rainfall event | Can the depression area fill in a 100yr ARI Future Scenario rainfall event if the outlet was totally blocked -either Yes or No |
SHAPE.STArea() / Max. flooded area in the 100yr ARI Future Scenario (m2) | Surface area of the depression (up to the spill elevation). |
Disclaimer:
In using the Catchments and Hydrology data set, you acknowledge that you have read, understood and agreed to the disclaimers below.
The flood plains and flood sensitive area data layers are generated from catchment level modelling based on the datasets, requirements and technology available at the time of model build. They are compiled regional layers with varied data uncertainty and currency, which may directly impact data accuracy for the area of interest. The information provided therefore does not preclude the need for appropriate site-specific assessment and cannot be construed as an endorsement or approval of any development by Auckland Council.
The Catchments and Hydrology data set is updated regularly when new information becomes available. As such, downloading and copying activities may result in data invalidity.
Whilst due care has been taken in producing the Catchments and Hydrology data sets, Auckland Council gives no warranty as to the accuracy and completeness of any information given and accepts no liability for any error, omission or use of the information.