Topic Options
#1468750 - 13/08/2018 22:21 August 1998 Wollongong Floods
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2619
Loc: Wollongong, NSW, Aus
20 years ago this week the Illawarra was ravaged by a savage ECL that dumped record rainfall leading to severe flooding,

Nine Wollongong are doing a 3-part series on this event:

https://www.facebook.com/WINNewsIllawarra/videos/457427584665994/

Top
#1468774 - 14/08/2018 11:25 Re: August 1998 Wollongong Floods [Re: Kino]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 526
Loc: Pinjarra Hills, Qld
In addition to the notable weather event, rainfall, and consequent flooding, this event was caused a paradigm shift in the flood research/engineering/council concerns about how urban drainage systems to small creeks and waterways are prone to debris blockage at culverts and small bridges.
Today it is recognised as a problem, but still very difficult to factor into flood risk maps, and most flood risk maps still don't take into account how much higher flood levels could be if bridges and culverts get blocked.
Here is a link to some technical discussion on the topic:
https://www.floodplainconference.com/papers2016/Rhys%20Hardwick%20Jones%20Full%20Paper.pdf
_________________________
Models are for estimating and gauges are for knowledge.

Top
#1468775 - 14/08/2018 12:02 Re: August 1998 Wollongong Floods [Re: Kino]
ozthunder Offline
Weatherzone Addict

Registered: 23/09/2001
Posts: 3184
Loc: Mt Warrigal, NSW, Australia
Seems to have lost some formatting over the years. But here is my report

http://www.ozthunder.com/diary/w98.htm
_________________________
Michael Thompson
http://ozthunder.com

Top
#1468776 - 14/08/2018 12:27 Re: August 1998 Wollongong Floods [Re: Kino]
ozthunder Offline
Weatherzone Addict

Registered: 23/09/2001
Posts: 3184
Loc: Mt Warrigal, NSW, Australia
Some other notes:

The system was lightning active, but mostly west of escarpment.

Storm just stalled for sveral hours just over and west of Illawarra escarpment adjacent to Wollongong's northern suburbs. Feed by humid NE winds up sloping and probably a convergence area just west of escarpment.

Boulders the size of cars were rolled over Bulli Pass.

Many motorists slept the night in their cars as access to Wollongong was limited.

In Shellharbour no flash flooding. I drove northwards in my old Patrol 4WD and only got as far as Cringila as there was a car bobbing around under the rail bridge at Five Islands Road.
_________________________
Michael Thompson
http://ozthunder.com

Top
#1468779 - 14/08/2018 13:05 Re: August 1998 Wollongong Floods [Re: Kino]
ashestoashes Offline
Weather Freak

Registered: 22/10/2017
Posts: 446
Loc: Voyager Point (South West Sydn...
I wonder if anyone has a synoptic map from this event.

Top
#1468860 - 15/08/2018 10:48 Re: August 1998 Wollongong Floods [Re: Kino]
ozthunder Offline
Weatherzone Addict

Registered: 23/09/2001
Posts: 3184
Loc: Mt Warrigal, NSW, Australia
Should also note that 1998 was an El Nino year, or were we coming out of it by August?
_________________________
Michael Thompson
http://ozthunder.com

Top
#1468867 - 15/08/2018 11:09 Re: August 1998 Wollongong Floods [Re: ozthunder]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2619
Loc: Wollongong, NSW, Aus
Originally Posted By: ozthunder
Should also note that 1998 was an El Nino year, or were we coming out of it by August?


Wasn't 98/99 a big La Nina?

Quote:
Although there was waxing and waning of intensity, the 35 months from May 1998 to March 2001 (Figure 1) can be considered one long La Niņa phase. It had a moderate to strong effect on a large area of the country; the south coast and Tasmania being the only areas missing out on the heavy falls. The NT had over 97% of its area in the highest decile of rainfall, while a high percentage of WA received record-high falls. Record-high totals were also prevalent about the northern NT, northeast Queensland and on the northwest slopes and plains of NSW.
The May 1998 to March 1999 (Figure 2) period followed a typical La Niņa pattern, both in terms of its timing from one autumn to the next and also with widespread above to very-much-above-average falls. The following six months from April to September 1999 (Figure 3) were considerably drier and seemed to mark a return to neutral conditions. However, the onset of the northern wet season saw a resurgence of La Niņa conditions, with widespread heavy rain over much of the country for the eight months from October 1999 to May 2000 (Figure 4). A pattern similar to the previous year then recurred with a dry spell from June to September 2000 (Figure 5) prior to a wet six months from October 2000 to March 2001 (Figure 6). With an Australia-wide average of 698 mm, the calendar year 2000 (Figure 7) was the second wettest year since 1900; only 1974 (760 mm) was wetter.
Flooding was rife during the three-year period, with tropical cyclones such as Thelma in December 1998, Rona in February 1999, Vance in March 1999, Steve in February and March 2000, Sam in December 2000 and Abigail in February 2001 all causing significant flooding in their wake. Substantial crop and stock losses were caused by widespread flooding in NSW and Queensland during July to September 1998 (Figure 8). Some regions had as many as four separate flooding incidents during these three months. There were also numerous hailstorms during this La Niņa, including the notorious Sydney hailstorm in April 1999, which is one of Australia�s most costly natural disasters in monetary terms.

Top
#1468894 - 15/08/2018 15:55 Re: August 1998 Wollongong Floods [Re: Kino]
Rainbow Spirit Offline
Weather Freak

Registered: 10/11/2010
Posts: 601
Loc: Green Valley, just west of Liv...
I came down with some SES members from Sydney on the 18th, and I well remember going into a house near Figtree, and talking to the residents. They said that their backyard, which backed onto a creek, had become a raging torrent in a matter of seconds, and washed their goat away, never to be seen again, and drowned a cockatoo in a cage when it got jammed against the roof of its cage.

When I went into the house there was a tide mark about a metre above the floor, but there was a step down in the mark in the back of the house, it seems that the back of the house had floated up when the framing snapped and the rear floated higher, then the rear of the house floated back down onto its foundations, thus the different tide marks.

Top
#1468920 - 16/08/2018 09:43 Re: August 1998 Wollongong Floods [Re: Kino]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2619
Loc: Wollongong, NSW, Aus
ozthunder - wasn't the '98 event the one that caused the landslip on Mt Keira?

Top
#1468971 - 17/08/2018 09:19 Re: August 1998 Wollongong Floods [Re: Kino]
ozthunder Offline
Weatherzone Addict

Registered: 23/09/2001
Posts: 3184
Loc: Mt Warrigal, NSW, Australia
Originally Posted By: Kino
ozthunder - wasn't the '98 event the one that caused the landslip on Mt Keira?


I actually think it wasn't, but the whole northern suburbs was on landslip alert after the floods - streets in Austimer and Thirroul. I had a mate that had unwittingly bought one of the landslip prone homes in Austimer. Had to get a lot of work done, but the view and $$$$$ now may have worth it.

That slip on Mount Kiera is not the first in that place.

Now I am wondering if in 6 months time the escarpment view will be like the 1969-1970 one. I lived in Primbee and you could after the October 1969 fires see the scout camp clearly for a few years. It has now sunk back into the forest.
_________________________
Michael Thompson
http://ozthunder.com

Top


Who's Online
7 registered (Mad Elf #1.5, DDstorm, Perfect Storm, Timbuck, Jimi, Homer, 1 invisible), 346 Guests and 1 Spider online.
Key: Admin, Global Mod, Mod
Today's Birthdays
bradmac, Eager2beastormchaser, Go The Cows, Roland
Forum Stats
29681 Members
32 Forums
23978 Topics
1500759 Posts

Max Online: 2925 @ 02/02/2011 22:23
Satellite Image