Nelson/Tasman Severe Rain Event - Dec 13-15

Archive of NZ Weather & Climate
Forum rules
These topics are a read-only archive and may be subject to out-of-date information.

For today's weather discussion head to: New Zealand Weather & Climate
User avatar
Nev
Moderator
Posts: 5724
Joined: Tue 07/03/2006 15:24
Location: Waiheke Island, Hauraki Gulf
Has thanked: 324 times
Been thanked: 619 times

Re: Heavy Rain Event - Dec 14-16

Unread post by Nev »

A few rainfall stat excerpts from Civil Defence's last update...
Nelson Tasman Civil Defence - Heavy rain update 12
5:27AM, 15 DECEMBER 2011

Rain has continued overnight but at a slower rate. River levels are continuing to fall and to date no further slips have been reported since late last night. ...

Summary of rainfall to date

The most significant falls of rain occurred in the lowland areas of Takaka and Richmond, and in the hills behind Nelson. Undoubtedly the most impressive rainfall total was that seen at the Kotinga gauge at Takaka Township, where (at 3am - and still raining) 510mm was recorded over 48 hours, with 423mm of that falling over a 24 hour period. In a record that spans back 35 years, the previous highest 24 hour total at this location was 256mm measured in August 1990. The 24 hour total seen yesterday was well in excess of a 1 in 100 year event.

On the Waimea plains the rainfall totals were smaller, but no less significant. Over 24 hours 200mm fell, also greater than a 1 in 100 year rainfall. These lowland falls combined with even larger rainfall totals in the Waimea and Maitai headwaters, where storm totals reached in excess of 400mm, with 329mm recorded in one 24 hour period at the head of the Brook Valley. ...

Code: Select all

Some rainfall totals recorded in the Nelson area for December 2011

Location                  24 hour total    48 hour total

Takaka at Kotinga              423               510
Anatoki at Happy Sams          368               451
Brook at Third House           329               402
Richmond at TDC Office         205               220
Roding at Caretakers           323               362
Also some MS 24 hr totals to midnight last night (odd that Westport has double that of the Airport?)...

Nelson Airport - 180.6 mm
Westport - 178.8 mm
Westport Airport - 92.0 mm
Hokitika Airport - 110.8 mm
Tim S
Posts: 379
Joined: Tue 26/09/2006 16:49
Has thanked: 0
Been thanked: 0

Re: Heavy Rain Event - Dec 14-16

Unread post by Tim S »

Can add 215mm for Atawhai - 36hr total - Nelson to that list Nev, with rain still falling. Lots of roads closed today with a few schools also closed, the kids are going to be most upset about that one!

Apparently rocks road is closed, so Waimea Rd is the only way into town, glad I live north of Nelson! :)
User avatar
snowstormwatcher
Posts: 1618
Joined: Wed 23/09/2009 09:45
Location: South Canterbury. 20km inland from Timaru.
Has thanked: 157 times
Been thanked: 125 times

Re: Heavy Rain Event - Dec 14-16

Unread post by snowstormwatcher »

I see there there was only 3mm recorded at Blenheim yesterday. Huge diffrence compared to Nelson.

looks like Maitai river in Nelson peaked to 228m3/sec which is huge for that river.
User avatar
TonyT
Moderator
Posts: 2765
Joined: Thu 08/05/2003 11:09
Location: Amberley, North Canterbury
Has thanked: 325 times
Been thanked: 987 times

Re: Heavy Rain Event - Dec 14-16

Unread post by TonyT »

Need to be careful with these return period estimates. It looks as though the 24 hour totals being quoted are peak values based on picking the highest period of 24 consecutive hours, whereas the return period data is probably based on 9am to 9am 24 hour totals. I may be wrong, but you cant compare apples with cherries.
Nev wrote:A few rainfall stat excerpts from Civil Defence's last update...
Nelson Tasman Civil Defence - Heavy rain update 12
5:27AM, 15 DECEMBER 2011

Rain has continued overnight but at a slower rate. River levels are continuing to fall and to date no further slips have been reported since late last night. ...

Summary of rainfall to date

The most significant falls of rain occurred in the lowland areas of Takaka and Richmond, and in the hills behind Nelson. Undoubtedly the most impressive rainfall total was that seen at the Kotinga gauge at Takaka Township, where (at 3am - and still raining) 510mm was recorded over 48 hours, with 423mm of that falling over a 24 hour period. In a record that spans back 35 years, the previous highest 24 hour total at this location was 256mm measured in August 1990. The 24 hour total seen yesterday was well in excess of a 1 in 100 year event.

On the Waimea plains the rainfall totals were smaller, but no less significant. Over 24 hours 200mm fell, also greater than a 1 in 100 year rainfall. These lowland falls combined with even larger rainfall totals in the Waimea and Maitai headwaters, where storm totals reached in excess of 400mm, with 329mm recorded in one 24 hour period at the head of the Brook Valley. ...

Code: Select all

Some rainfall totals recorded in the Nelson area for December 2011

Location                  24 hour total    48 hour total

Takaka at Kotinga              423               510
Anatoki at Happy Sams          368               451
Brook at Third House           329               402
Richmond at TDC Office         205               220
Roding at Caretakers           323               362
Also some MS 24 hr totals to midnight last night (odd that Westport has double that of the Airport?)...

Nelson Airport - 180.6 mm
Westport - 178.8 mm
Westport Airport - 92.0 mm
Hokitika Airport - 110.8 mm
User avatar
Nev
Moderator
Posts: 5724
Joined: Tue 07/03/2006 15:24
Location: Waiheke Island, Hauraki Gulf
Has thanked: 324 times
Been thanked: 619 times

Re: Heavy Rain Event - Dec 14-16

Unread post by Nev »

TonyT wrote:Need to be careful with these return period estimates. It looks as though the 24 hour totals being quoted are peak values based on picking the highest period of 24 consecutive hours, whereas the return period data is probably based on 9am to 9am 24 hour totals. I may be wrong, but you cant compare apples with cherries.
Yes, I did wonder about the return periods, although they're not too far off the 9am totals. As a comparison, here's a few figures to 9am this morn, c/o NIWA's Cliflo database (note that Nelson and Hokitika are both airport sites, just slightly apart from each other)...

Code: Select all

Rainfall to 9am, Dec 15 2011
Location                         24 hrs   48 hrs   72 hrs  

Takaka Ews (NIWA)                 392.2    547.8    565.0       
Nelson Aero (N/A)                 167.9    248.2    252.4   
Nelson Aws (Metservice)           154.8    234.2    240.8   
Appleby 2 Ews (NIWA)               98.8    171.2    178.0   
Westport Aero Aws (Metservice)     68.0     98.4    101.8   
Hokitika Aero (N/A)                68.5    122.0    136.9   
Hokitika Aws  (Metservice)         64.8    112.4    127.0   
jamie
Posts: 5855
Joined: Fri 25/02/2011 21:35
Location: Hamilton NZ
Has thanked: 22 times
Been thanked: 256 times
Contact:

Re: Heavy Rain Event - Dec 14-16

Unread post by jamie »

why on earth would you bother making the return periods 9am-9am. If it is then thats just silly. its adding a huge amount of chance into the equation. a rain period is simply that. if 500mm fell in 48hours then thats what happened. but if you start looking at 9am-9am then your possibly/more than likely going to be skipping parts of the event. a river will flood based on how much has fallen. the river isnt going to somehow get rid of the rain that fell before 9am or after 9am and only flood based on the rain it received between 9am-9am.
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland
Has thanked: 342 times
Been thanked: 361 times

Re: Heavy Rain Event - Dec 14-16

Unread post by NZstorm »

Historically weather readings for climate were taken at 9am.
User avatar
Tornado Tim
Moderator
Posts: 4894
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton
Has thanked: 91 times
Been thanked: 174 times
Contact:

Re: Heavy Rain Event - Dec 14-16

Unread post by Tornado Tim »

NZstorm wrote:Historically weather readings for climate were taken at 9am.
Only in NZ and Aus as far as I am aware.

I keep the Reset times at Midnight for my weather station, mainly for the logic behind the day ending then.
Now this will lead onto a Reset time debate, LOL
If it is make up an a new thread for it please and dont carry it on here.
P.S I am new mod here now (so treat me nicely ;) )
NZAPStrike.net - NZ Aus Pacific Strike Network
jamie
Posts: 5855
Joined: Fri 25/02/2011 21:35
Location: Hamilton NZ
Has thanked: 22 times
Been thanked: 256 times
Contact:

Re: Heavy Rain Event - Dec 14-16

Unread post by jamie »

NZstorm wrote:Historically weather readings for climate were taken at 9am.
actually yes i didnt think about the historical factor of that rainfall hasnt always been measured in real time. so knowing how much rain fell in how long was not recorded.
Tim S
Posts: 379
Joined: Tue 26/09/2006 16:49
Has thanked: 0
Been thanked: 0

Re: Heavy Rain Event - Dec 14-16

Unread post by Tim S »

Umm not sure why there isn't a seperate thread for the events in the Nelson/Tasman Region, surely a state of Emergency warrants a seperate thread does it not???

Anyway, just got back from a long shoft at the Emergency Operations Centre and all I can say is Wow! What a day, have never really been involved in a disaster of this magnitude and it was truly amazing how much rain we got and it has only just stopped. Around 200 slips in the Nelson/Tasman Region some very large ones, with major problems with infrastructure expected. Not sure how much I can say as it may not be released to the public but I can assure everyone the Maitai dam isn't going to burst (people in Nelson where worried of this) but there may be other problems with the water supply to Nelson if remedial work doesn't help.

275mm in my gauge from the last 42hrs or so, truly epic fall for this area! :eek:
User avatar
Tornado Tim
Moderator
Posts: 4894
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton
Has thanked: 91 times
Been thanked: 174 times
Contact:

Re: Heavy Rain Event - Dec 14-16

Unread post by Tornado Tim »

Tim S wrote: 275mm in my gauge from the last 42hrs or so, truly epic fall for this area! :eek:
Sure is, what was your peak and average rain rate for the event?
NZAPStrike.net - NZ Aus Pacific Strike Network
User avatar
Nev
Moderator
Posts: 5724
Joined: Tue 07/03/2006 15:24
Location: Waiheke Island, Hauraki Gulf
Has thanked: 324 times
Been thanked: 619 times

Re: Heavy Rain Event - Dec 14-16

Unread post by Nev »

Tim S wrote:Umm not sure why there isn't a seperate thread for the events in the Nelson/Tasman Region, surely a state of Emergency warrants a seperate thread does it not???
Done. :smile:
Tim S
Posts: 379
Joined: Tue 26/09/2006 16:49
Has thanked: 0
Been thanked: 0

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Tim S »

Thanks nev!

No idea about rainfall rates as I was using a manual gauge. I'd imagine they didn't exceed 10-12mm/hr though going by readings from other gauges in the region. A bit of rough calculations though 280mm (was abit more after I emptied it) over 48 hrs gives 5.8mm/hr, which is amazing really!

More showers on the way for this arvo by the looks of things which is the last thing we need.
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island
Has thanked: 0
Been thanked: 0
Contact:

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Manukau heads obs »

amazing photos here
http://www.stuff.co.nz/national/6163937 ... thers-land
and reports of over 700mm in 48 hours
which is Cyclone Bola sort of stuff (and the damage looks the same)
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
Brassnz
Posts: 257
Joined: Thu 14/10/2004 12:42
Location: Laingholm, Auckland
Has thanked: 35 times
Been thanked: 4 times

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Brassnz »

On the radio this morning Marcus Lush (RadioLive) commented that the 764mm recorded over that 48hr period was an all-time record for rainfall over 48hrs in any urban centre in NZ. Ever. Quite a claim. Anyone know if there's any truth to it? If there was, I'd have thought it would be widely reported as it would be an unprecedented event in our short history.
User avatar
Nev
Moderator
Posts: 5724
Joined: Tue 07/03/2006 15:24
Location: Waiheke Island, Hauraki Gulf
Has thanked: 324 times
Been thanked: 619 times

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Nev »

^ Was it a private reading? Those are fantastic amounts for 48 hours, but possible I guess.

Here's a slightly modified Rainfall Report I managed to grab from Tasman District Council sites at the time. I'm pretty sure the 24 hour return periods are to midnight NZST (1am NZDT). Note that although for example, 'Takaka at Kotinga' recorded 677mm over 3 calendar days, nearly all of that would have fallen over the 48 hrs from late Tuesday arvo (13th) until late Thursday arvo (15th)...

Code: Select all

7 Day Rainfall Report during Dec, 2011 - c/o Tasman District Council

Site Name                   17th    16th    15th    14th    13th    12th    11th     Total 

Anatoki at Happy Sams        1.0     4.5   110.0   366.0    57.5    23.0     0.0     562.0
Anatoki at Paradise          1.5    11.5    93.5   343.5    60.0    35.0     1.0     546.0
Aorere at Devils Boots                      44.0   201.0    44.0    25.0     0.5     314.5
Aorere at Perry Saddle       0.5     8.5    60.5   281.0    43.5    47.5     1.5     443.0
Aorere at Salisbury Br       2.0     7.0    37.0   272.0    40.5    29.5     0.0     388.0
Baton at Baton Flats         0.0     3.5     7.5    13.0     3.0     7.5     0.0      34.5
Brook at Third House         0.0     3.0   132.0   323.5    73.5    11.0     0.0     543.0
Buller at Longford           0.0     4.5     0.5    12.0     0.5     0.5     0.0      18.0
Kainui Dam                                  21.0    96.5     5.5     2.0     0.0     125.0
Lee at Trig F                0.0     4.0    54.5   172.5    26.5     4.0     0.5     262.0
Maitai at Forks              0.0     1.0    95.5   217.0    39.5     2.5     0.0     355.5
Motueka at Gorge             0.5     3.5    11.0    52.0     3.5     2.5     0.0      73.0
Motueka at Red Hills         0.0     6.5    14.5    30.0     3.5     3.0     0.0      57.5
Motueka at Woodstock         0.0    16.0    10.5    10.0     1.5     5.5     0.0      43.5
Motupiko at Christies        0.0     7.5    11.5    48.0     0.5     1.0     0.0      68.5
Moutere at Kellings Rd                      16.0    67.0    12.5     7.5     0.0     103.0
Orphanage at Ngawhatu                       80.5   215.0    14.0     5.5     0.0     315.0
Riwaka North at Littles      0.0    10.0    22.0    88.0    13.0    12.0     0.0     145.0
Riwaka South at Moss Bush    0.5     8.0    18.0    71.5     9.5     8.0     0.0     115.5
Roding at Caretakers         0.0     1.0    95.0   312.0    46.0     6.0     0.0     460.0
Tadmor at Mudstone           0.0     4.5    20.0    30.5     3.5     8.0     0.0      66.5
Takaka at Harwoods           0.0     2.0    50.0   183.5    25.5     7.0     0.0     268.0
Takaka at Kotinga            2.0     5.0   169.6   418.9    88.4    17.9     0.0     701.8
Wai-iti at Belgrove                         20.5    92.0     8.5     4.0     0.0     125.0
Waimea at TDC Nursery        0.0     1.0    57.0   196.0    16.5     7.0     0.0     277.5
Waingaro at Hanging Rock     0.5     4.0    76.0   286.5    52.5    17.0     0.0     436.5
Waingaro at Little Devil     2.0    12.5    32.5   182.5    33.5    14.0     1.5     278.5 
Wairoa at Irvines            0.0     2.0    44.0   170.5    12.0     3.0     0.0     231.5
Wakapuaka at Hira                          153.0   209.0    20.5     5.5     0.0     388.0
Wangapeka at Biggs Tops      0.0     1.5     9.0    29.0    10.0     3.5     0.0      53.0
Wangapeka at Walter Peak     0.0     3.5    16.0    15.5     3.5    12.0     0.0      50.5 

Btw, Cropp River in the Hokitika River catchment holds the 48 hour rain record with 1049mm in Dec, 1995 (along with most other rainfall records), but there'd probably be few sites that have come anywhere near that. ;-)

Edit: Bit more info added.
User avatar
Richard
Posts: 7849
Joined: Tue 14/07/2009 07:32
Location: Amuri basin,Inland North Canterbury
Has thanked: 1205 times
Been thanked: 546 times

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Richard »

Still, an impressive rainfall rate at Takaka at Kotinga of 701.8mm over that period 8-o
Tim S
Posts: 379
Joined: Tue 26/09/2006 16:49
Has thanked: 0
Been thanked: 0

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Tim S »

Amazing graphic representation here of the significance of this rainfall event:
http://nelsontasmancivildefence.co.nz/a ... infall.pdf
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island
Has thanked: 0
Been thanked: 0
Contact:

Re: Nelson/Tasman Severe Rain Event - Dec 13-15

Unread post by Manukau heads obs »

the Takaka hill sure is a big road block for northerly rain
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
Locked