Christchurch Flooding

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BTR

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#141221 5-Mar-2014 10:37

Wondering how everyone is getting on down here in CHCH with flooding. I have a bit of flooding at work but my house is fine only a very soggy lawn.

Hopefully no there aren't any floating data centres.

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#999359 5-Mar-2014 11:46

Dunbars road in Halswell and flowing into Lincoln road is an utter mess. All the run off ponds are flooding something chronic.

Our building at work has leaked yesterday.

tdgeek

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#999366 5-Mar-2014 12:03

Local stream two houses down, which runs very low is up t the bridge. Risen about 2 metres. Beckenham

jbard

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#999369 5-Mar-2014 12:08

Anybody got any photos of the floods?

SumnerBoy

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#999371 5-Mar-2014 12:16

http://www.stuff.co.nz/the-press/news/your-weather/9792495/Sumner-Akaroa-under-water

mikerussellnz

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#999373 5-Mar-2014 12:19

City library has posted some photos.
http://www.flickr.com/photos/christchurchcitylibraries/sets/72157641871904154

Fred99

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#999386 5-Mar-2014 12:33

Weather is clearing now.
I just went from Mt Pleasant to the city and return. Low lying areas have copped it - Heathcote river overflowing. I came across a few people in cars - stalled in floodwater with the water half way up their doors. I don't know what gets in to people trying stuff like that - unless you give them the benefit of doubt - that they were trying to shift cars which were already getting inundated.
Lots of tree branches and mess everywhere.
I guess one of the big questions will be about flooded homes in areas which have sunk due to the EQs, but have not been red-zoned or compensated for this as "land damage". New flood level rules based on sea-level rise allowed for much larger flood events than this one -= which is being talked about as the biggest flooding in 25 years - but I have my doubts it's been much worse than what we get every few years.
In the area of the hills where we are, damage is mainly due to run-off, that exacerbated by stormwater systems which have never been fixed since the quakes.
We did have a lot of water getting under our house post-quake, trying to cut it off "at source" would have probably been impossible, so I got a drainlayer to dig a trench about 1.5-2m deep on the uphill side, lay novaflow running in to a new sump, then back to the stormwater system. In a rare example of cooperation, EQC actually agreed to pay for it as "land damage", the amount they allowed actually allowed me to do get the work done, and it's been well and truly tested over the past couple of days - passed with flying colours as the sub-floor is bone dry. I'm guessing that this rain will be causing all sorts of difficult issues on the hill suburbs, as well as the more obvious problems with flooding on the flat.

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Shoes2468

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#999397 5-Mar-2014 12:52

Fred99: Weather is clearing now.
I just went from Mt Pleasant to the city and return. Low lying areas have copped it - Heathcote river overflowing. I came across a few people in cars - stalled in floodwater with the water half way up their doors. I don't know what gets in to people trying stuff like that - unless you give them the benefit of doubt - that they were trying to shift cars which were already getting inundated.
Lots of tree branches and mess everywhere.
I guess one of the big questions will be about flooded homes in areas which have sunk due to the EQs, but have not been red-zoned or compensated for this as "land damage". New flood level rules based on sea-level rise allowed for much larger flood events than this one -= which is being talked about as the biggest flooding in 25 years - but I have my doubts it's been much worse than what we get every few years.
In the area of the hills where we are, damage is mainly due to run-off, that exacerbated by stormwater systems which have never been fixed since the quakes.
We did have a lot of water getting under our house post-quake, trying to cut it off "at source" would have probably been impossible, so I got a drainlayer to dig a trench about 1.5-2m deep on the uphill side, lay novaflow running in to a new sump, then back to the stormwater system. In a rare example of cooperation, EQC actually agreed to pay for it as "land damage", the amount they allowed actually allowed me to do get the work done, and it's been well and truly tested over the past couple of days - passed with flying colours as the sub-floor is bone dry. I'm guessing that this rain will be causing all sorts of difficult issues on the hill suburbs, as well as the more obvious problems with flooding on the flat.

certainly not clearing here in riccarton, certainly the wind has dropped but is still pouring with rain.

tdgeek

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#999446 5-Mar-2014 13:46

Shoes2468:
Fred99: Weather is clearing now.
I just went from Mt Pleasant to the city and return. Low lying areas have copped it - Heathcote river overflowing. I came across a few people in cars - stalled in floodwater with the water half way up their doors. I don't know what gets in to people trying stuff like that - unless you give them the benefit of doubt - that they were trying to shift cars which were already getting inundated.
Lots of tree branches and mess everywhere.
I guess one of the big questions will be about flooded homes in areas which have sunk due to the EQs, but have not been red-zoned or compensated for this as "land damage". New flood level rules based on sea-level rise allowed for much larger flood events than this one -= which is being talked about as the biggest flooding in 25 years - but I have my doubts it's been much worse than what we get every few years.
In the area of the hills where we are, damage is mainly due to run-off, that exacerbated by stormwater systems which have never been fixed since the quakes.
We did have a lot of water getting under our house post-quake, trying to cut it off "at source" would have probably been impossible, so I got a drainlayer to dig a trench about 1.5-2m deep on the uphill side, lay novaflow running in to a new sump, then back to the stormwater system. In a rare example of cooperation, EQC actually agreed to pay for it as "land damage", the amount they allowed actually allowed me to do get the work done, and it's been well and truly tested over the past couple of days - passed with flying colours as the sub-floor is bone dry. I'm guessing that this rain will be causing all sorts of difficult issues on the hill suburbs, as well as the more obvious problems with flooding on the flat.

certainly not clearing here in riccarton, certainly the wind has dropped but is still pouring with rain.

Daughter there said that too. Our creek that rose about two metres is slowly going down.

Fred99

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#999478 5-Mar-2014 14:19

I see The Press is quoting the CCC now calling it a "100 year event".
I doubt it - the impact might be one in 100 year, but that's because some land had sunk, stormwater systems are damaged etc.

sen8or

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#999591 5-Mar-2014 16:22

Meanwhile somewhere in Christchurch......

mattwnz

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#999620 5-Mar-2014 17:26

Fred99: I see The Press is quoting the CCC now calling it a "100 year event".
I doubt it - the impact might be one in 100 year, but that's because some land had sunk, stormwater systems are damaged etc.

It maybe a sign that there is something seriously wrong with both the infrastructure and the land since the EQs. I think it is going to lead to a lot more money needing to be spent somehow on new stormwater drainage. Was not really the smartest place to build a city.

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UncleArk

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#999622 5-Mar-2014 17:28

Fred99: I see The Press is quoting the CCC now calling it a "100 year event".
I doubt it - the impact might be one in 100 year, but that's because some land had sunk, stormwater systems are damaged etc.

Describing the storm event as a 100yr event is simply a a function of event duration and rainfall intensity measured in mm/h.

In other words, the amount of rain that has fallen in ChCh per hour over the last 24 hours is the equivalent of an event which has an annualised probability of occuring being 1% (or 1 in 100).

In actuality at times the storm event was about a 120yr return period event.

mattwnz

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#999623 5-Mar-2014 17:35

UncleArk:
Fred99: I see The Press is quoting the CCC now calling it a "100 year event".
I doubt it - the impact might be one in 100 year, but that's because some land had sunk, stormwater systems are damaged etc.

Describing the storm event as a 100yr event is simply a a function of event duration and rainfall intensity measured in mm/h.

In other words, the amount of rain that has fallen in ChCh per hour over the last 24 hours is the equivalent of an event which has an annualised probability of occuring being 1% (or 1 in 100).

In actuality at times the storm event was about a 120yr return period event.

It is also a way of saying that it isn't normal, so it shouldn't recoccur again in a lifetime. So there isn't necessarily anything that needs to be done to the infrastructure in the future as it won't happen again for 100 years. The problem is that you do often see one in a hundred year even reoccurring in certain areas quite regularly.

UncleArk

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#999625 5-Mar-2014 17:37

mattwnz:
Fred99: I see The Press is quoting the CCC now calling it a "100 year event".
I doubt it - the impact might be one in 100 year, but that's because some land had sunk, stormwater systems are damaged etc.

It maybe a sign that there is something seriously wrong with both the infrastructure and the land since the EQs. I think it is going to lead to a lot more money needing to be spent somehow on new stormwater drainage. Was not really the smartest place to build a city.

While there are certainly operational difficulties in the post-quake environment with the open and piped stormwater drainage network in Christchurch it must be appreciated that the design capacity of the street side channels ("gutters") and piped systems is typically to serve a 10yr event.

Even a fully operation system will over-top, gorge, and overflow in severe rainfall events as we have just experienced.

Fred99

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#999645 5-Mar-2014 17:53

UncleArk:
Fred99: I see The Press is quoting the CCC now calling it a "100 year event".
I doubt it - the impact might be one in 100 year, but that's because some land had sunk, stormwater systems are damaged etc.

Describing the storm event as a 100yr event is simply a a function of event duration and rainfall intensity measured in mm/h.

In other words, the amount of rain that has fallen in ChCh per hour over the last 24 hours is the equivalent of an event which has an annualised probability of occuring being 1% (or 1 in 100).

In actuality at times the storm event was about a 120yr return period event.

Not according to data I'm looking at.
Just over 70mm of rain in 48 hours. Highest in 1 hour was 4.8mm.
It was nothing out of the ordinary - only slightly above mean annual recorded maximums.
See page 7.
See also page 20, where in 1986 floods, more rainfall was recorded in 24 hours (Chch Gardens) than the 48 hour recording for this latest event.
http://resources.ccc.govt.nz/files/NIWA.pdf

I don't believe it was a "100 year event" at all.

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