This analysis provides a brief assessment of how flooding could affect the State Highway network within Palmerston North. The purpose is to demonstrate some analysis techniques of diverse data sets, rather than to produce a serious engineering-level impact study.
Flood-prone areas from the PNCC district plan were combined with State Highway geometries from LINZ to identify where roads intersect with areas susceptible with flooding. Traffic monitoring site locations and daily vehicle counts from NZTA were then used to estimate how many vehicles would be affected if these highways were distrupted by flooding.
Four main State Highway corridors within Palmerston North intersect flood-prone areas. These locations represent the areas where flooding is most likely to disrupt traffic on the State Highway network. For each corridor, the nearest NZTA traffic monitoring site was identified, and traffic counts were used to estimate potential disruption.
The summary table below presents the affected roads/State Highways, the nearest monitoring sites, and the average number of vehicles and heavy vehicles expected to be impacted each day.
The map illustrates the spatial relationships between the flood-prone zones and the transport network, enabling users to explore the specific locations of potentially vulnerable highway sections.
| Monitoring site | Affected State Highways | Avg vehicles/day | Heavy vehicles (%) | Flooded SH segments |
|---|---|---|---|---|
| Flygers Line | SH 3 | 6479 | 5.2 | 2 |
| Mangaone Bridge | SH 56 | 4990 | 3.3 | 1 |
| Pahiatua Track | SH 57 | 2191 | 13.1 | 1 |
| Ashhurst | SH 3 | 1344 | 7.0 | 2 |