Hawkesbury River Flood – The aftermath – 26 March 2021

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Floodwaters are now receding and the extent of the damage is becoming obvious. My wife and I returned to Windsor Friday afternoon 26 March 2021 to view the water levels. Floodwaters at that time were still high but receding and the new Windsor Bridge was clearly visible again.

Much rubbish, litter, tree branches and furniture items had washed downstream and unlike last Sunday, the floodwaters now had a distinct brown muddy colour and an odour.

Roads were still closed including the Windsor Bridge with assessors viewing the bridge for damage and with cleaning crews undertaking a mammoth cleaning task.

Floodwaters rose at least 2 metres in height along the Windsor Riverwalk and much scouring of soil had occurred. A distinct brown mark had been left on trees to show how high the waters came.

The cleanup will take some time and insurance costs will take time to tally. Preliminary estimates would suggest that this event will exceed $1 billion but it is too early to verify this. This event has been declared a catastrophe.

The extent of the flooding on Thursday can clearly be seen on this NASA Worldview image at a scale of 10 km from Earth orbit. The flood is seen as a muddy brown river with the floodwaters across North West Sydney clearly visible.

The photos attached show some of the cleanup that is needed at Windsor Bridge and other locales and there is a need to remove debris and even entire trees that had toppled over.

The rain event that caused this was prolonged across 5 or 6 days which is unusual and many coastal localities received more than 300 mm of rain with some areas receiving more than 400 mm of rain.

There are exceptions to this including Mt Seaview which received 815 mm of rain in 5 days during this event, Kempsey has received 819 mm of rain in 19 days this month including 758 mm of rain during the event.

All photos attached to this event were taken Friday afternoon 26 March 2021 around Windsor.

Hawkesbury River Major Flooding – 21 to 24 March 2021

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The Hawkesbury River basin in western Sydney at the base of the Blue Mountains passes through Penrith, Richmond and Windsor. Within this area, a number of flood plains exist that are prone to flooding and there have been numerus floods recorded over the years.

The topography of the river basin contributes to the flooding in which there are five tributaries but only one outlet to let the water out.

Since 1961, there have been 29 floods recorded with the 1961 event being the largest since the construction of Warragamba Dam.

Perhaps the most significant flood according to known records is the 23 June 1867 event where a flood peak of approximately 19.7 metres was recorded at Windsor. Windsor, Richmond, and Pitt Town at that time became small islands according to records. It is also understood that 12 people from the Eather Family were killed during this event.

The largest flood since the construction of Warragamba Dam was the November 1961 event in which waters reached at least 14.2 metres (Some articles suggest up to 14.5 metres) in height at Windsor.

The current flood along the river while a significant event (Most likely a 1 in 50 year event) does not and will not reach the levels of 1961 or 1867.

The current flood peak appears to have passed with the river reaching a maximum flood peak of 12.48 metres at Windsor SWC and 12.93 metres at Windsor PWD and there is evidence to suggest that the river level may have started to fall although slowly.

It is identified on the attached graph that the major flood level at Windsor Bridge is 12.2 metres and as at 7.16 pm Wednesday evening, the river has been at major flood level for over 57 hours. This is a considerable amount of time for the river to be at major flood level.

The new Windsor Bridge which was thought to be high enough has failed its first major test with the bridge being submerged especially across the western side.

The images attached to this post were taken on Sunday afternoon prior to the maximum flood peak occurring.

This is certainly a major event with significant damage across the region to homes, infrastructure and cropping land and it is known that insurance will become an issue over coming days as claims are made.

On Tuesday 23 March, Cumberland City Council engineers explained to me in graphic detail the true potential for flooding for this area using the latest available flood maps. It is clear that higher floods have the potential to engulf much more of Richmond and Windsor urban area than that seen at the present time and it must be emphasized that this appears to be a 1 in 50 year event.

Heavy rain has again been a feature although a significant clearing trend passed over Sydney after 3 pm on Tuesday afternoon with the rain ceasing and cloud clearing out to sea. This will allow a cleanup to commence as flood waters recede.

For the 24 hours to 9 am 22/3/2021 the most significant rainfalls were:-

Sydney region

Kurrajong Heights - 147 mm

Colo Heights - 105 mm

Shanes Park - 90 mm

Penrith - 88 mm.

North Coast

Mt Seaview - 203 mm.

Woolgoolga - 182 mm.

Kempsey - 180 mm.

Elands - 174 mm.

Utungun - 172 mm

Coffs Harbour - Up to 182 mm.

Willina - 166 MM.

Such scenes are repeated up and down the New South Wales coast and even into south east Queensland with significant flood events on other north coast rivers occurring simultaneously.

For the 24 hours to 9 am 24/3/2021, the most significant rainfalls were limited to the far south coast including:-

Mt Darragh 162 mm.

Bodalla 127 mm.

Brogo Dam 116 mm.

Rainfall across Sydney eased considerably Tuesday with the highest total occurring at Stone Quarry Creek being 74 mm  and up to 35 mm around Campbelltown in the south west and at Portable to the north west.

The rainfall has ceased across most of New South Wales and affected areas which will now allow for a cleanup to commence which will take considerable time.

Major flooding with photos at Richmond and Windsor – 21 March 2021

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Following excessive rainfall on Saturday and into Sunday 21/3/2021, my wife and I decided to take an afternoon drive into the Hawkesbury River basin to see the impacts of the current rain event across Sydney.

The photos attached to this post are taken within an area stretching from south of Penrith north to Richmond and Windsor.

We were initially planning to go to Warragamba Dam to see the overspill occurring however, just to the south of Penrith, we encountered flood waters covering the road that made travel too dangerous.

While the road south of Penrith to Warragamba Dam was still open, it was evident that SES personnel were monitoring road travel and its closure was imminent. I was informed by the SES at that location that Warragamba Dam itself had been closed to the public.

We travelled north to Richmond and encountered numerous flooding impacts on both sides of the road and at Richmond, I took photos of flooding scenes that I have never seen before.

At Windsor, the Nepean River was exceptionally high and the new road bridge (Putty Road) was closed due to flood waters lapping close to the road level. My wife and I witnessed a steel drum being washed downstream hitting the road bridge.

As a result, Putty Road itself was closed to traffic in both directions.

Furthermore, floodwaters were so high that Windsor Road at Pitt Town was closed and the 4 lane road itself was inundated with deep floodwaters. I have never seen this level of flooding before and the images show the scale of the event.

Heavy rain has inundated Sydney overnight into Sunday morning and several suburbs received more than 100 mm including Hornsby - 120 mm and Penrith - 105 mm. Warragamba Dam received 157 mm, Katoomba received 168 mm and Blackheath received 140 mm for the 24 hours to 9 am 21/3/2021.

It should be noted that anyone venturing into the Nepean River basin needs to be aware of road closures, flood levels, SES and Police personnel who are monitoring road conditions and roads could easily be closed with little or no notice.

All the images were taken Sunday afternoon 21 March 2021.