Cork City flood -again

Nerdlingr wrote: »

Clonmel's flood defence barriers

Grand if you want to pretend the river doesn't exist

jetfiremuck

Dredging for the most part is the least intrusive and quickest method of seeing results. tidal barriers cost wise will end like the childrens hospital....overruns, not even thinking about eco analysis etc.

blindsider

alanucc wrote: »

The channel capacity in the western half of the city centre gets exceeded at much lower flows than 2009. See this map for an idea - the 10%AEP (i.e. small flood) still floods out

I don't want to get into debating 2009 either, but would note that fluvial flood risk on the Lee is very real and "natural" - similar events to 2009 occurred in 1853, 1875 and 1916, all before the dams were built and before climate change started to bite. I think it would be foolish to think that similar events will never happen again (whether they will in our lifetime is another matter)

I'm certainly not discounting major fluvial events, but I am concerned about events such as yesterday which seem all too regular.

I'd be interested to know how many of the previous flood events were tidal v fluvial

I appreciate the fact-based arguments (from e.g. AlanUCC) and I'll happily declare my lack of knowledge in this area.

I do have significant concerns that the OPW seem wedded to a scheme which is unsightly, potentially expensive (even compared to a tidal barrier), difficult to implement and maintain and less effective than another proposal.

Separately, I've seen no mention of dredging apart from a couple of short comments here.

Flooding in Cork city is likely to continue every year from now on. Sea levels are rising and a 0.5M rise is likely by the end of the century. Added to that is the fact that Cork is sinking into the ocean, I could be wrong but the rate is 1 cm every ten years!

Is it time to move and rebuild further inland and leave certain areas to the inevitable?

alanucc

blindsider wrote: »

I'd be interested to know how many of the previous flood events were tidal v fluvial

Have a look at figure 2-1 on page 4 here

Mefistofelino

blindsider wrote: »

I'm certainly not discounting major fluvial events, but I am concerned about events such as yesterday which seem all too regular.

I'd be interested to know how many of the previous flood events were tidal v fluvial

I appreciate the fact-based arguments (from e.g. AlanUCC) and I'll happily declare my lack of knowledge in this area.

I do have significant concerns that the OPW seem wedded to a scheme which is unsightly, potentially expensive (even compared to a tidal barrier), difficult to implement and maintain and less effective than another proposal.

Separately, I've seen no mention of dredging apart from a couple of short comments here.

Whatever about the OPW costs for their scheme, the idea that the tidal barrier can be constructed for €170 million seems utter mince. The shortest the barrier can be is approximately 1km which, coincidently, is about the same length as the tidal barrier in Cardiff which consists of a long stone barrage with a number of navigable gates in the middle. Twenty years ago, the Cardiff project ended up around £220 million (and has had quite a deleterious impact on the bay). Even the relatively piddley Bridgwater tidal barrier is now looking like costing more over £100 million (and it hasn't started yet).

Perhaps a tidal barrier is a better solution than the OPW proposal but we need to be going into it with our eyes fully open.

fonzy951

saabsaab wrote: »

Flooding in Cork city is likely to continue every year from now on. Sea levels are rising and a 0.5M rise is likely by the end of the century. Added to that is the fact that Cork is sinking into the ocean, I could be wrong but the rate is 1 cm every ten years!

Is it time to move and rebuild further inland and leave certain areas to the inevitable?

The Dutch have much greater issues with sea level rise than Cork and seem to have no problem in solving them, even reclaiming land from the sea. Every part of Cork city can be very easily protected, the Dutch would have no bother with it, that's for sure. They would probably get a fit of laughing if they saw the state of the existing quays, especially on Morrison's Island.

alanucc

saabsaab wrote: »

Added to that is the fact that Cork is sinking into the ocean, I could be wrong but the rate is 1 cm every ten years!

It's more like 0.5mm/year. Sorry don't have a source to hand

alanucc wrote: »

It's more like 0.5mm/year. Sorry don't have a source to hand

Fair enough, 1cm every 20 years.

fonzy951 wrote: »

The Dutch have much greater issues with sea level rise than Cork and seem to have no problem in solving them, even reclaiming land from the sea. Every part of Cork city can be very easily protected, the Dutch would have no bother with it, that's for sure. They would probably get a fit of laughing if they saw the state of the existing quays, especially on Morrison's Island.

They don't have the direct wild atlantic hitting them with as much force. Also there is the expected earthquake tsunami which could destroy any vulnerable costal areas.

sheff_

saabsaab wrote: »

They don't have the direct wild atlantic hitting them with as much force. Also there is the expected earthquake tsunami which could destroy any vulnerable costal areas.

Cork City is 20km upriver from Roches Point. We're not exactly taking a Lahinch style battering from the Atlantic. I'm sure North Sea storms can give the Dutch anything we see in Cork.

Mefistofelino

fonzy951 wrote: »

The Dutch have much greater issues with sea level rise than Cork and seem to have no problem in solving them, even reclaiming land from the sea. Every part of Cork city can be very easily protected, the Dutch would have no bother with it, that's for sure. They would probably get a fit of laughing if they saw the state of the existing quays, especially on Morrison's Island.

While the Dutch are masters at flood management, it's not exactly been "no problem" . Protecting the country has had a massive financial cost. Even the annual cost of maintenance and remediation of the existing defenses is in the billions .
And even then, it hasn't always been successful - it's not even 70 years since the floods of 58 when about 10% of the country ended up under water and over 1800 people died.

But you're dead right, they'ld laugh at the scale of our issues.

Mefistofelino wrote: »

While the Dutch are masters at flood management, it's not exactly been "no problem" . Protecting the country has had a massive financial cost. Even the annual cost of maintenance and remediation of the existing defenses is in the billions .
And even then, it hasn't always been successful - it's not even 70 years since the floods of 58 when about 10% of the country ended up under water and over 1800 people died.

But you're dead right, they'ld laugh at the scale of our issues.

Maybe we could ask them to come over and give us a quote for the job?

blindsider

Ah but we did!

https://www.irishexaminer.com/news/arid-20470398.html

Experts at the Delft University (TU Delft) in the Netherlands, who were asked to review the OPW’s €450m-€1bn cost estimate of a tidal barrier at Little Island, say they believe it could be built for just under €200m.

They described the tidal barrier proposal as “an interesting and attractive option” which warrants further investigation.

The report was commissioned by the Save Cork City (SCC) group, which is leading the opposition to the OPW’s reliance on raised quay walls as part of its Cork flood defence plan.

SCC has repeatedly called for the construction of a tidal barrier at Little Island to protect the city from flooding and released a report it commissioned last year from HR Wallingford which put the cost at between €110m and €180m.

However, the OPW has repeatedly ruled out a tidal barrier on cost and engineering grounds, insisting it could cost anything from €450m to €1bn and while possible from an engineering perspective, it would do nothing to prevent fluvial or river flooding of Cork city centre.

However, SCC said the emergence of this second independent report which questions the OPW’s cost estimates shows that the tidal barrier option must be considered further.

The TU Delft experts said it appears from their review of the OPW’s costs that the body applied a unit rate for tidal sector gates to simpler tidal sluice gates — an approach it said is “not considered appropriate” and which would result in an “unrealistic cost estimate”.

On their first review of the tidal barrier costs, they said a tidal barrier at Little Island could cost around €258m, with the comparable OPW cost of €340m.

A second review would result in a cost below €200m, they said.

The development of a more detailed, and project-specific cost estimate for the Little Island tidal barrier is highly recommended, the experts said.

The Irish Examiner asked the OPW to comment on the TU Delft conclusions and recommendations but a spokesman said the agency could not comment on a report it has not seen in full.

SCC spokesman John Hegarty said the tidal barrier represents the best solution for the city.

“There is still time to address the issue and not destroy Cork with the walls scheme,” he said.

I presume the OPW found the time to review this report......?

Most of the businesses and buildings that flooded ,are the same buildings that always flood ... And a lot of the time not by a lot ,
City council could pass a byelaw requiring building owners to put flood barriers in front of their entrances ,(and non return valves on the sewer pipes )

It wouldn't fix every problem ,but it'd be a start , some Morrison's island / south terrace works are pretty necessary as well ....

Dropping the level of the water at carrigadroichead ,would seriously reduce flood risk from the lee ,and restore the geragh ,and could be done at a stroke ..

blindsider wrote: »

Ah but we did!

https://www.irishexaminer.com/news/arid-20470398.html

Experts at the Delft University (TU Delft) in the Netherlands, who were asked to review the OPW’s €450m-€1bn cost estimate of a tidal barrier at Little Island, say they believe it could be built for just under €200m.

They described the tidal barrier proposal as “an interesting and attractive option” which warrants further investigation.

The report was commissioned by the Save Cork City (SCC) group, which is leading the opposition to the OPW’s reliance on raised quay walls as part of its Cork flood defence plan.

SCC has repeatedly called for the construction of a tidal barrier at Little Island to protect the city from flooding and released a report it commissioned last year from HR Wallingford which put the cost at between €110m and €180m.

However, the OPW has repeatedly ruled out a tidal barrier on cost and engineering grounds, insisting it could cost anything from €450m to €1bn and while possible from an engineering perspective, it would do nothing to prevent fluvial or river flooding of Cork city centre.

However, SCC said the emergence of this second independent report which questions the OPW’s cost estimates shows that the tidal barrier option must be considered further.

The TU Delft experts said it appears from their review of the OPW’s costs that the body applied a unit rate for tidal sector gates to simpler tidal sluice gates — an approach it said is “not considered appropriate” and which would result in an “unrealistic cost estimate”.

On their first review of the tidal barrier costs, they said a tidal barrier at Little Island could cost around €258m, with the comparable OPW cost of €340m.

A second review would result in a cost below €200m, they said.

The development of a more detailed, and project-specific cost estimate for the Little Island tidal barrier is highly recommended, the experts said.

The Irish Examiner asked the OPW to comment on the TU Delft conclusions and recommendations but a spokesman said the agency could not comment on a report it has not seen in full.

SCC spokesman John Hegarty said the tidal barrier represents the best solution for the city.

“There is still time to address the issue and not destroy Cork with the walls scheme,” he said.

I presume the OPW found the time to review this report......?

Great post, thanks. I read somewhere that the walls idea won't work anyway.

cantalach

blindsider wrote: »

Experts at the Delft University (TU Delft) in the Netherlands, who were asked to review the OPW’s €450m-€1bn cost estimate of a tidal barrier at Little Island, say they believe it could be built for just under €200m.

[...]

The report was commissioned by the Save Cork City (SCC) group, which is leading the opposition to the OPW’s reliance on raised quay walls as part of its Cork flood defence plan.

I’m not qualified to say whether a tidal barrier would be better or worse. But I do know that when reading any report done by academics and their grad students, one of the most important things to look at is is who funded the work. When I worked in that environment 25 years ago, our sponsors always got the results they wanted...

MyPeopleDrankTheSoup

€180m for the cork tidal barrier of 1km length when Maeslantkering in Holland cost €660m for a third of the length?

We should go with SaveCorkCity's proposal if they guarantee to pay any cost over their €180m!

MyPeopleDrankTheSoup wrote: »

€180m for the cork tidal barrier of 1km length when Maeslantkering in Holland cost €660m for a third of the length?

We should go with SaveCorkCity's proposal if they guarantee to pay any cost over their €180m!

Even if it costs at much as the OPW finger-in-the-air estimate it protects multiples of the area with at least twice the lifespan so good value in my book.

If the opw are going to do it then think of a large number , double it , ... Now broaden the project ...
Clench your buttocks when the consulting engineers come back with a works estimate ... ( That part has now swallowed your original budget ) tender it ...
Then estimate to pay double the the original tender for related works ...

Oh and make sure the scheme needs just one more component to work .. ( but you didn't build that ) ,
And that there's a special key needed, buts held by a bloke who's on holidays in majorca when the flood water hits ...
And that's for either the city quays or a harbour flood barrier ...

MyPeopleDrankTheSoup wrote: »

€180m for the cork tidal barrier of 1km length when Maeslantkering in Holland cost €660m for a third of the length?

We should go with SaveCorkCity's proposal if they guarantee to pay any cost over their €180m!

Anybody coming out with numbers for a tidal barrage at this stage , (high or low ) is pretty much guessing... Where would you put it , what's the depth there , what's underneath the water ,? What are you going to build the barrier out of ,and where's that coming from ,? What are you protecting against , and will it be still effective in 20 / 50 years time ...
What environmental effect would it have , how long would you need to do an environmental impact study for , and what would the budget be to ameliorate that ...

Oh yeah and from a city council point of view ,if a flood barrier was to be built by opw somewhere up the harbour ... Who'd pay for repairing the current quay walls ?and whatever public realm improvements that the city would like done ... Because at the moment that will be the opw coming up with all that money... And each section done would kind of lead on to the next section needing to be done ,domino style ...

Fair point, the council are getting a freebie out of this why wouldn't they support it.

MyPeopleDrankTheSoup

TheChizler wrote: »

Even if it costs at much as the OPW finger-in-the-air estimate it protects multiples of the area with at least twice the lifespan so good value in my book.

the €180m is from the SaveCorkCity crowd. The OPW say it would be around €1billion for a tidal barrier, which sounds more realistic

cantalach

MyPeopleDrankTheSoup wrote: »

the €180m is from the SaveCorkCity crowd. The OPW say it would be around €1billion for a tidal barrier, which sounds more realistic

Thames Barrier cost £534M between 1974 and 1984, i.e. billions in today’s money. Very different river so probably a meaningless comparison, but still.