METHODOLOGY
3.1 Modelling Approach
The hydraulic model prepared for this study utilised a linked 2D version of the TUFLOW HPC (Heavily
Parallelised Compute) model. For this flood study, a Direct Rainfall (also known as Rain on Grid) modelling
approach has been utilised; rainfall data inputs with model losses defined based on catchment surface
characteristics generate surface runoff, which is then hydraulically routed through the model topography. More
detail on the modelling
The weather stats are in for 2024 and if you live near Hawken Road in South Taranaki then last year you will have enjoyed the lowest rainfall and highest air temperature in the region. And those living near Ngutuwera, north of Waitotara, had to hang onto their hats on 4 February as the area recorded the highest wind gust for the year at 128.52km/hr. Figures from Taranaki Regional Council show the region, well known for enjoying a healthy dose of rain most years, recorded 14% less than normal
rain gauge sites in Taranaki.
October Year to Date
Rain gauge # days
with rain
Total
rain
(mm)
% of
typical
month
Total to
date (mm)
% of typical
year to date
% of typical
full year
Records
Began
North Egmont at
Visitors Centre 19 625.5 85.4 4948.9 84.7 71.6 1995
Dawson Falls 17 569.5 100.4 4825.0 88.1 75.4 1999
Kapoaiaia at Kahui
Hut 21 490.5 102.4 3868.5 87.0 73.6 2006
Mangorei Upper at
Forest Hill 18 250.5 80.6 2469.0 80.8 65.8
year-to-date totals for rain gauge sites in Taranaki.
July Year to Date
Rain gauge # days
with rain
Total
rain
(mm)
% of
typical
month
Total to
date (mm)
% of typical
year to date
% of typical
full year
Records
Began
North Egmont at
Visitors Centre 17 592.5 84.8 2774.5 73.6 39.9 1991
Dawson Falls 19 672.5 109.2 2821.0 83.3 47.4 1933
Kapoaiaia at Kahui
Hut 20 356.0 61.7 2279.0 77.8 43.4 2006
Mangorei Upper at
Forest Hill 17 257.0 63.3 1493.5
Rainfall September and year-to-date totals for rain gauge sites in Taranaki.
September Year to Date
Rain gauge # days
with rain
Total
rain
(mm)
% of
typical
month
Total to
date (mm)
% of typical
year to date
% of typical
full year
Records
Began
North Egmont at
Visitors Centre 23 492.7 73.5 4323.4 84.6 62.5 1995
Dawson Falls 24 483.5 76.1 4255.5 86.7 66.5 1999
Kapoaiaia at Kahui
Hut 25 452.0 89.8 3378.0 85.2 64.2 2006
Mangorei Upper at
August and year-to-date totals for rain gauge sites in Taranaki.
August Year to Date
Rain gauge # days
with rain
Total rain
(mm)
% of
typical
month
Total to
date (mm)
% of typical
year to date
% of typical
full year
Records
Began
North Egmont at
Visitors Centre 19 1064.2 156.0 3830.7 86.3 56.5 1994
Dawson Falls 18 967.5 145.5 3772.0 89.1 58.8 1998
Kapoaiaia at Kahui
Hut 24 650.5 123.4 2926.0 84.5 58.4 2005
Mangorei Upper at
Forest Hill 18
Dry conditions in South Taranaki caused by the current La Nina weather pattern could mean further restrictions on how much water can be taken from rivers, Taranaki Regional Council has warned. The environmental watchdog is keeping a close eye on rainfall levels, soil moisture, river flows and climate across the region, with most of the Council’s monitoring sites recording less rain than usual over the last three months. Council data for the lowest rainfall sites shows Pātea recorded 61% of
year-to-date totals for rain gauge sites in Taranaki.
June Year to Date
Rain gauge # days
with rain
Total
rain
(mm)
% of
typical
month
Total to
date (mm)
% of typical
year to date
% of typical
full year
Records
Began
North Egmont at
Visitors Centre 15 466.5 68.7 2182.0 71.0 31.4 1991
Dawson Falls 14 513.0 82.2 2148.5 77.5 36.1 1933
Kapoaiaia at Kahui
Hut 16 344.0 63.0 1923.0 81.8 36.6 2006
Mangorei Upper at
Forest Hill 14 188.5 55.5 1236.5
river beds. As of last week, five of the seven monitored river sites and one lake were unsuitable for swimming (for humans or dogs) due to cyanobacteria (toxic algae). We will continue to monitor these sites until they return to normal, posting the results on LAWA each week. We’ll do a full analysis of the summer’s results, but most of the samples that exceeded guideline levels were taken after heavy or prolonged rain. We know heavy rain washes contaminants off the land into rivers and out to sea.
December continued 2024’s trend for lower rainfall with an average of 108.3mm - 34% less than usual. On average across Taranaki there was 14% less rainfall than normal across all rain gauges with year-to-date rainfall lowest at Waitōtara at Hawken Rd with 28% less than usual. In December, there was 63% less rain at Kaupokonui at Glenn Rd and 11% less at Motunui M39 at Weston W3. Mean river flows for December were 31.8% lower than typical values, low flows were 21.9% greater, and high flows