Overland flow paths (OLFPs) were re-mapped for the Auckland region in 2019 by WSP using LiDAR data flown in 2016 and 2017. The OLFPs were re-mapped using a 1m DEM formed from ground points. Nearly 6,000 manual adjustments to the DEM were used to map the overland flow paths in flat and depression areas.

OLFPs were identified using GIS techniques and are not based on hydraulic modelling.

Peak flow rates and runoff volumes for 2-, 10- and 100-year annual recurrence interval (ARI) and 90th and 95th percentile events have been attributed to each overland flow path, following the graphical method outlined in Guidelines for Stormwater Runoff Modelling in the Auckland Region: Technical Publication 108 (TP108). Both the existing scenario (existing imperviousness and rainfall) and the future scenario (future development and rainfall due to climate change) are represented here; two climate change scenarios were considered, viz., temperature increases of 2.1 and 3.8 degrees-C.

The aim of this dataset is to provide a regionally consistent validation tool for runoff calculations and hydraulic modelling to assist consultants, contractors, development engineers, catchment managers and hydraulic modelling staff.

A copy of the full background report can be obtained from the Regional Planning team in Auckland Council’s Healthy Waters department. The data will be updated on an ad hoc basis to align with updates to Auckland Council’s LiDAR data.

Vertical Datum: NZVD1946