Overland Flow Path Mapping for the Wellington Region

Overland flow paths and depression areas have been mapped for 17 catchments in Wellington City. Overland flow paths represent the predicted path of stormwater as it flows over the topography. They can be mapped using specialist GIS software and LiDAR data.

In addition to delineating flow paths, the peak flow for the 1% Annual Exceedance Probability (AEP) rainfall event was estimated using a computer algorithm to implement the rational method. The peak flows (and associated parameters required to estimate the peak flow) were provided for each overland flow segment, providing useful spatial information that can be retrieved from GIS databases with the click of a button. As well as providing thematic mapping options, the estimation of flow also provides a method for categorising and assessing the risk to not just flooding but other hazards such as contaminant mobilisation.