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Flooding and the ESB....
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25-11-2009 5:52pm#1There are three main causes of flooding:
1. Nature – (eg a lake on a hill or mountain with no man made involvement)
2. Bad planning and design (eg a concrete jungle with poor drainage provision)
3. People asleep at the wheel while “managing” hydro electricity stations and similar
The massive tsunami that was created when the sluce gates at the Inniscarra dam near Cork city were opened in a fit of panic last Thursday (most/all of them simultaneously apparently) clearly falls into the third category. The negligence caused perhaps €300M+ of damage to the city and region, and untold inconvenience to householders and businesses that have been deprived of tap water supplies since.
It is after all a 44 m high (14 story building) wall of water ready to escape if something structural fails. Open all the sluce gates and the 44 m wall of water goes on the rampage, knocking down quay walls etc.
It doesn’t matter how much rain fell over a short period on Thursday – reservoir levels should be maintained at a sufficiently low level so that reserve spare capacity remains to deal with extreme downpours and is always available. Even downpours that might happen every 10,000 years – because a downpour of this magnitude could happen next week.
There was a (minor by comparison) flood event in Cork in 2000, and ESBI produced a report on the incident. Table 6.1 in this report predicts a rainfall inflow of 1,311 m3/sec in a mega one in ten thousand year event. Logically, the levels in that reservoir should not be allowed to exceed a point where it would be incapable of dealing such an event today and every day. The inflows last Thursday were reported at a piffling 800 m3/sec by comparison.
This has to be done by proactively dumping water when the tide is out – so that the river system downstream has maximum capacity to deal with the flow without causing flooding. Thursday’s (19.11.2009) panic water dumping took place at high tide – the worst possible time!
The main purpose of the dam (given that it exists) should be protecting the city – the few kW of electricity produced by this ageing system are immaterial in the big picture. If the dam was not there, there would be no flood risk to the city – because there would be no build up of water.
Cork has had floods in the past – (eg November 2000, February 1997, etc) reports on which are hidden at the OPW’s www.floodmaps.ie website, (presumably to prevent google and other search engines linking to them) - the same mechanism prevents me from linking to them here.....
The spin about “800 tonnes of water per second coming down the valley” etc was reproduced uncritically by the media. Poor helpless ESB one might think. Aside from prudential timely reservoir level management, it seems to me that there is a burden of proof on the ESB to produce the facts in some more detail – eg rain gauge data for the 7 days up to Thursday – they have six rain gauges at various points along the valley, which collect and transmit data on a half-hourly basis.
One article I came across reported claims that “four inches” of rain (ie 101 mm) fell in a few hours on Thursday. This is difficult to believe in the context of rainfall recorded by Met Éireann rain gauges in the region. Cork Airport recorded 51.2 mm for the 24 h period ending midnight on Thursday. Roche’s Point at the mouth of Cork harbour recorded 37.2 mm. Sherkin Island in West Cork recorded 39.8 mm. It is difficult to believe that over 100 mm of rain fell in the Lee Valley on the same day – within a few hours!
In the “River Lee flood of November 2000” report, table 4.1 shows the rainfall recorded at six rain gauges in the week leading up to the flood averaging 128 mm for the week – with a maximum of 140 mm at one of the gauges. Unfortunately these rain gauge data are not available on the internet.
Dear ESB, please disclose your rain gauge data for the 6 gauges in question for the 7 days to midnight on Thursday.
If one looks at figure 5.2 in the same report, there is a chart showing the recorded water levels, discharge and inflow in the Nov 2000 flood, as well as the rainfall. I would like to see a similar chart published for the ten day period to 21.11.2009. Looking at the chart traces in the 2000 event it is clear that the ESB personnel were asleep at the wheel in terms of water level management. While the reservoir level starts rising rapidly from the evening of 26.11.2000, they don’t start to increase the discharge (from 100 to 150 m3/sec) until half-way through the 28th – despite the continuously heavy rainfall. It is only after the inflow spikes (almost a day after the spike) that the discharge is increased from 150 to 275 m3/sec. The discharges should have been running at a rate of at least 200 m3/sec continuously (outside high tide peaks) from early on the 26th.
The safe water level should be set at something less than 48 mOD (to use their antiquated measurement system), and water level gauges should be installed at critical points downstream along the river, to report in real-time back to the control system in Inniscarra when downstream river levels are reaching critical levels.
Met Éireann’s presentation of weather information could also be improved on their website. It is a false economy to restrict or dumb down the quality and availability of weather information when one considers the massive cost of this single flooding event.
While they have a three-hour forecast which shows anticipated rainfall in detail in each part of the country, they need similar levels of detail covering the next 6, 12, 18, 24, 30 and 36 hours. The Spanish meteo service offer this service for wind, precipitation, temperature and other information, using the same HIRLAM model as is used by Met Éireann. The detailed forecast numbers from HIRLAM should also be published in text files to enable anybody interested (local authorities, utilities, householders, farmers etc) run an Excel spreadsheet to automatically pick up the data of interest to them over their internet connection. This would allow people to make calculations and build their own mathematical models to enable them to minimise the risks to their business, community or household.
Detailed access to good weather forecasting is essential for efficient energy use - whether you run a wind farm, have solar panels, or store heat in one form or another as part of your energy management system.
This event should be a wake-up call to everybody. Extreme weather events have to be intelligently managed for using the best available information.
Report on the 2000 flood referred to above:
https://sites.google.com/site/probeinfosite/docs/floodreportleevalley2000.pdf?attredirects=0&d=1
HIRLAM forecast Spain showing detailed rainfall and other projections up to 48 hours in advance:
http://www2.aemet.es/web/infmet/modnum/hirlam.html
(click on 00 or 12, Superficie, and H+06 and Precipitation etc to reveal map)
The Spanish site measures rainfall in l/m2 (litres per square meter).
1 mm of rain falling on the ground = 1 litre of water per square meter
1 tonne of water = 1 m3 (cubic meter) = 1,000 litres
Some journos resort to imperial measurements to dumb things down and confuse even more:
4 imperial inches of rain = more or less 100 mm = 100 litres of water per m20
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What?The massive tsunami
Basis?The negligence caused perhaps €300M+ of damage to the city
One section of quay wall?knocking down quay walls etc.
I imagien this would mean that the reservoir would need to be kept empty.It doesn’t matter how much rain fell over a short period on Thursday – reservoir levels should be maintained at a sufficiently low level so that reserve spare capacity remains to deal with extreme downpours and is always available. Even downpours that might happen every 10,000 years – because a downpour of this magnitude could happen next week.0 -
Rubbish! Do the numbers for yourself. Carrigadrohid reservoir has a surface area of 9 km2. Inniscarra is 5 km2. That is 14 km2 (ignoring other lakes upstream etc). For every one meter you reduce the permitted water level limit, you get an additional emergency storage for 14 million tonnes of water. 14 million tonnes buys you capacity to handle an extra 5 hours of torrential rain at 800 tonnes a second flow rate or 3 hours at the 1,300 tonnes per second once in 10,000 year freak situation. The Iniscarra wall is 44 m high. The system can still hold a lot of water if you reduce permitted maximum levels by a few meters.What?
I imagien this would mean that the reservoir would need to be kept empty.
As for the cost, one will have to wait and see the total of the insurance claims when they come in. If the insurers manage in passing the cost on to the ESB, the regulator should ensure that ESB prices aren’t allowed to be increase to compensate them.
The quay wall in question didn’t collapse for nothing. It has stood the test of time. There must have been a huge force of energy behind the surge of water that hit it. The dam is 10 km of windy river upstream of the damaged wall.
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=cork&sll=53.41291,-8.24389&sspn=5.095588,16.907959&g=ie&ie=UTF8&hq=&hnear=Cork,+County+Cork+City,+Ireland&ll=51.881578,-8.816872&spn=0.164881,0.528374&z=120 -
There is one main cause of flooding:
1. Nature
FYP
(people being allowed and actually build in flood planes is a different matter)Rubbish! Do the numbers for yourself. Carrigadrohid reservoir has a surface area of 9 km2. Inniscarra is 5 km2. That is 14 km2 (ignoring other lakes upstream etc). For every one meter you reduce the permitted water level limit, you get an additional emergency storage for 14 million tonnes of water. 14 million tonnes buys you capacity to handle an extra 5 hours of torrential rain at 800 tonnes a second flow rate or 3 hours at the 1,300 tonnes per second once in 10,000 year freak situation. The Iniscarra wall is 44 m high. The system can still hold a lot of water if you reduce permitted maximum levels by a few meters.
I do partially agree, although the math is not that simple (Inniscarra and Carrigadrohid reservoirs are not 14km2 at the bottom, so they don't hold quite that much water).
Additonaly other (uncrontrollable) streams other than the Inniscara dam feed into the Lee prior to flowing through the city.
Sean_84 posted a link to a water level measuring station of the Lee in Cork in this post
From this data it seems though that the ESB have been releasing water for a week previous to the flooding and possibly only held back water for less than half a day to help with the search of the missing person.0 -
FYP (people being allowed and actually build in flood planes is a different matter)
I do partially agree, although the math is not that simple (Inniscarra and Carrigadrohid reservoirs are not 14km2 at the bottom, so they don't hold quite that much water).
Additonaly other (uncrontrollable) streams other than the Inniscara dam feed into the Lee prior to flowing through the city.
Sean_84 posted a link to a water level measuring station of the Lee in Cork in this post
From this data it seems though that the ESB have been releasing water for a week previous to the flooding and possibly only held back water for less than half a day to help with the search of the missing person.
Thanks for the link to the Malting's water level gauge. Of course the reservoirs aren't 14 km2 in area at the bottom. There must be a sense of priorities and prudence. There is no alternative to reducing the maximum permitted level of the water by at least 2m. Period! :-)
PS: The real chart we need to see is the figure 5.2 chart (from the 2000 flood report) for the few weeks up to last Friday.....0 -
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They were searching the river for a body which meant the level was kept lower than normal. Later that day the ESB released reasonable amounts of water from the reservoir to prevent the thing overflowing causing large scale flooding in the area and possibly causing the eventual collapse of the dam.
This would clearly have been much worse than simply letting the controlled volume out.
If the dam were not there the flooding probably would have been much worse as the system would not have been able to drain such a volume of water so quickly. as it was the dam was able to absorb much of this water build up and reduce flooding in the whole region greatly. the volume of water that fell over the week meant that regardless of anything else there was going to be flooding somewhere in the region.0 -
FYP (people being allowed and actually build in flood planes is a different matter)
I was talking to a friend yesterday and he saw flood maps from the 19th century of Cork showing flood depths and most of the areas that were flooded were showing at least 3ft and up to 9ft of historical flood levels.
So to say that this is a once in 800 yr event is a little wide of the mark.
Regarding building on flood plains I agree, but even the new Cork City council library was built with a basement! What planning allowed that?
Not to mention the irreparable loss of artwork when the UCC art library flooded.
There are far to many engineers and planners that are making decisions that are incompetent to do so.0 -
Cookie_Monster wrote: »They were searching the river for a body which meant the level was kept lower than normal. Later that day the ESB released reasonable amounts of water from the reservoir to prevent the thing overflowing causing large scale flooding in the area and possibly causing the eventual collapse of the dam.
This would clearly have been much worse than simply letting the controlled volume out.
If the dam were not there the flooding probably would have been much worse as the system would not have been able to drain such a volume of water so quickly. as it was the dam was able to absorb much of this water build up and reduce flooding in the whole region greatly. the volume of water that fell over the week meant that regardless of anything else there was going to be flooding somewhere in the region.
You are missing the point! I'm saying take the max allowed level 2m lower, and this will give you the spare capacity in time to search for bodies and other emergencies as well as deal with extreme rainfall.
The existing regulations governing water levels are obviously not working - hence the floods and panic discharges.
The Iniscarra dam (along with Ardnacrusha) are part of Ireland's aging, neglected infrastructure. Reducing levels by 2 m lightens the pressure load on the system by 28 million tonnes. It is grossly irresponsible to continue with the status quo.0 -
I was talking to a friend yesterday and he saw flood maps from the 19th century of Cork showing flood depths and most of the areas that were flooded were showing at least 3ft and up to 9ft of historical flood levels.
You are confusing two issues. The floods in the streets of Cork in the 19th century were a function of the low level of the streets in high tide conditions. High tide came in (eg spring tide), streets got flooded, and water came up drains (because the drains dumped water into the river directly). That flooding could happen in a drought year, when the Lee Valley had low levels of water.
This thread is about the ESB dams and their contribution to flooding.0 -
A question for the number crunchers; if the dam wasn't there, what level would you estimate the waters would have reached in the city?0
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Cork still floods on an almost annual basis. The main factors are a spring tide, an easterly wind and low air pressure typically associated with rainy weather. Perhaps 40% of the flow of the River Lee comes from the Bride, Shournagh and Curraheen Rivers, which are not controlled by any dam.
Probably another metre higher or more.Deleted User wrote: »A question for the number crunchers; if the dam wasn't there, what level would you estimate the waters would have reached in the city?0 -
Deleted User wrote: »A question for the number crunchers; if the dam wasn't there, what level would you estimate the waters would have reached in the city?
Probably impossible to calculate accurately.
The 'published' facts so far are:
- Maximum inflow into the Inniscarra dam was about 800 m3/sec (couldn't find an in dependant source for that so far)
- Maximum outflow of the Inniscarra dam was 535 m3/sec (so, although 'releasing' water they actually seem to have held back the highest peak flow)
- The Inniscarra dam only compromises about 60% (not quite sure on that number) of the catchment area of the Lee flowing through the city, so the remaining 40% are not 'controlable'.
This would indicate that there would have been about 1/3 more water flowing though the city if the dam wouldn't have been there....
Again, I might be wrong, but these are the data that I could get so far....
As for the water level estimate... sorry I wouldn't know how to calculate that (but it's definitely not 1/3 higher than what was experienced)0 -
Thanks, that's what I suspected, but didn't have the info to work it out.
Too many are looking for a scapegoat and the ESB are an easy target.
For many of the flooded buildings built since the last large flood, then it's just the consequences of bad planning.0 -
So why can't we have the data that the ESB used to base their decision on be published. As far as I can ascertain much of the spin they have been feeding to the media does not add up.0
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Probably impossible to calculate accurately.
The 'published' facts so far are:
- Maximum inflow into the Inniscarra dam was about 800 m3/sec (couldn't find an in dependant source for that so far)
- Maximum outflow of the Inniscarra dam was 535 m3/sec (so, although 'releasing' water they actually seem to have held back the highest peak flow)
- The Inniscarra dam only compromises about 60% (not quite sure on that number) of the catchment area of the Lee flowing through the city, so the remaining 40% are not 'controlable'.
This would indicate that there would have been about 1/3 more water flowing though the city if the dam wouldn't have been there....
Again, I might be wrong, but these are the data that I could get so far....
As for the water level estimate... sorry I wouldn't know how to calculate that (but it's definitely not 1/3 higher than what was experienced)
You have controllable factors and factors beyond control within the existing system. Thursday evening's flood was driven by opening the sluce gates at Inniscarra on the main river Lee. The logic behind a "new normal" regulation maximum water level in the reservoirs is to maximise the ability to control events.
The River Bride is uncontrolled, has a record discharge of 50 tonnes per second, and it is fed from a different hydrological system, so it is unlikely to be maxing out at the same time as the main River Lee. 50 tonnes /sec is tiny in the context of the 800 tonnes risk from the main river.
There is no alternative to imposing a "new normal" regulatory maximum reservoir height which is say 2 m lower than allowed under the current regime. The cost is minimal. There is no excuse for not doing it.0 -
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Thursday evening's flood was driven by opening the sluce gates at Inniscarra on the main river Lee.
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The River Bride is uncontrolled, has a record discharge of 50 tonnes per second, and it is fed from a different hydrological system, so it is unlikely to be maxing out at the same time as the main River Lee. 50 tonnes /sec is tiny in the context of the 800 tonnes risk from the main river.
Read my post again. With the so far published facts (some independent) the Inniscarra dam actually held back water!!
The 800 m3/sec is the INFLOW of the dam, the 50 m3/sec of the river Bride is therefore more than significant with the maximum 535 m3/sec outflow.
(could you actually link to your source of the 50m3/sec please?)There is no alternative to imposing a "new normal" regulatory maximum reservoir height which is say 2 m lower than allowed under the current regime. The cost is minimal. There is no excuse for not doing it.
I agree, this is probably the cheapest solution if possible. (Although the ESB is not going to like it as they will produce less electricity....).
Putting it in relation though... this was a very rare event (1 in 800 years according to pre-'global warming' calculations if you believe in that thing), so we probably won't see that again in our lifetime.0 -
Read my post again. With the so far published facts (some independent) the Inniscarra dam actually held back water!!
The 800 m3/sec is the INFLOW of the dam, the 50 m3/sec of the river Bride is therefore more than significant with the maximum 535 m3/sec outflow.
(could you actually link to your source of the 50m3/sec please?)
I'm not arguing that the dam held back NO WATER. My simple argument is that more reserve for emergencies should be kept available all the time with a new normal max water height. This would allow discharges to be managed rather than having to take place in a "panic".
The flow rate of the Bride is in sec. 5.4 of the report I linked to in my root posting -
https://sites.google.com/site/probeinfosite/docs/floodreportleevalley2000.pdf?attredirects=0&d=1. The precise number quoted is 53 tonnes/sec on 21.10.1988.
It is a matter of priorities - do you want to extract every last kWh of electricity from this system (which is small anyway in the context of Ireland's current needs in 2009) - at a phenomenal cost in terms of insurance claims, inconvenience and no water in people's taps for over a week?I agree, this is probably the cheapest solution if possible. (Although the ESB is not going to like it as they will produce less electricity....).
The insurance claims total for this one event would probably buy over 200 MW of wind turbine capacity - which capacity would last for about 25 years. It is a no-brainer!0 -
90mm of rain in one day.
http://www.irishtimes.com/newspaper/ireland/2009/1128/1224259620533.htmlESB says no option but to release water
BARRY ROCHE Southern Correspondent
LEE VALLEY: THE ESB has strongly defended its role in the flooding of the Lee Valley and insisted it had no alternative but to release water from Inniscarra Dam due to unprecedented rainfall over a 24-hour period.
The semi-State company has been criticised by many in Cork over its decision to release a large quantity of water from Inniscarra last Thursday. Moreover, some politicians have called for an independent inquiry into the decision.
However, Inniscarra plant station manager Liam Buckley said it was only through action taken by ESB staff at Inniscarra and Carrigadrohid dams that a much greater flooding disaster was averted.
Mr Buckley said that the ESB monitors Met Éireann forecasts and changes in water levels in the 306sq mile catchment of the river Lee. The company was aware of high ground-water levels and forecasts of heavy rain for last week.
He explained that the normal capacity of the Lee Valley reservoir system is 35 million cubic metres of water with the Inniscarra reservoir accounting for 19 million cubic metres of this and the Carrigadrohid reservoir further upstream having a 16 million cubic metre capacity.
Other factors which must be considered with regard to the discharge from Carrigadrohid and Inniscarra is that some 40 per cent of the Lee Valley catchment is not governed by dams as both the Shournagh and Bride tributaries are downstream of Inniscarra.
On November 16th, with water levels starting to rise, the ESB issued a flood warning in accordance with the Local Authority Emergency Response Plans. It began discharging water from Inniscarra at a rate of 150 cubic metres per second, said Mr Buckley.
According to Mr Buckley, a discharge rate of approximately 150 cubic metres per second can be contained within the banks of the Lee downstream of the dam without a threat of flooding. But as water continued to enter the system, the ESB was forced to ramp out discharge.
Maximum allowable water level at the dam is 50.9m above sea level and levels, which had risen on Monday, were brought down to approximately 48.3m metres by Wednesday without any downstream flooding as discharges were kept at 150 cubic metres per second.
In the Lee Valley the ESB’s monitoring stations found 90mm of rain fell in a 24-hour period and a flood warning was issued before 11am, Mr Buckley said.
According to Mr Buckley, water entering the catchment rose to a peak of approximately 800 cubic metres per second, forcing the ESB to allow water levels behind the dam rise to 50.86m – 4cms below the dam’s maximum operating level.
The ESB was forced to further increase the discharge rate from Inniscarra in accordance with flood control regulations to a peak discharge on Thursday night of 535 cubic metres per second which kept water levels more than a metre below the 52-metre high crest of the dam, This peak discharge marked a one-third reduction in the magnitude of the flood which, given the water entering the Lee system, would, were it not for Inniscarra and Carrigadrohid, have led to uncontrolled flooding causing even more extensive damage to Cork city, he said.0 -
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There are three main causes of flooding:
1. Nature – (eg a lake on a hill or mountain with no man made involvement)
2. Bad planning and design (eg a concrete jungle with poor drainage provision)
3. People asleep at the wheel while “managing” hydro electricity stations and similar
The massive tsunami that was created when the sluce gates at the Inniscarra dam near Cork city were opened in a fit of panic last Thursday (most/all of them simultaneously apparently) clearly falls into the third category. The negligence caused perhaps €300M+ of damage to the city and region, and untold inconvenience to householders and businesses that have been deprived of tap water supplies since.
It is after all a 44 m high (14 story building) wall of water ready to escape if something structural fails. Open all the sluce gates and the 44 m wall of water goes on the rampage, knocking down quay walls etc.
It doesn’t matter how much rain fell over a short period on Thursday – reservoir levels should be maintained at a sufficiently low level so that reserve spare capacity remains to deal with extreme downpours and is always available. Even downpours that might happen every 10,000 years – because a downpour of this magnitude could happen next week.
There was a (minor by comparison) flood event in Cork in 2000, and ESBI produced a report on the incident. Table 6.1 in this report predicts a rainfall inflow of 1,311 m3/sec in a mega one in ten thousand year event. Logically, the levels in that reservoir should not be allowed to exceed a point where it would be incapable of dealing such an event today and every day. The inflows last Thursday were reported at a piffling 800 m3/sec by comparison.
This has to be done by proactively dumping water when the tide is out – so that the river system downstream has maximum capacity to deal with the flow without causing flooding. Thursday’s (19.11.2009) panic water dumping took place at high tide – the worst possible time!
The main purpose of the dam (given that it exists) should be protecting the city – the few kW of electricity produced by this ageing system are immaterial in the big picture. If the dam was not there, there would be no flood risk to the city – because there would be no build up of water.
Cork has had floods in the past – (eg November 2000, February 1997, etc) reports on which are hidden at the OPW’s www.floodmaps.ie website, (presumably to prevent google and other search engines linking to them) - the same mechanism prevents me from linking to them here.....
The spin about “800 tonnes of water per second coming down the valley” etc was reproduced uncritically by the media. Poor helpless ESB one might think. Aside from prudential timely reservoir level management, it seems to me that there is a burden of proof on the ESB to produce the facts in some more detail – eg rain gauge data for the 7 days up to Thursday – they have six rain gauges at various points along the valley, which collect and transmit data on a half-hourly basis.
One article I came across reported claims that “four inches” of rain (ie 101 mm) fell in a few hours on Thursday. This is difficult to believe in the context of rainfall recorded by Met Éireann rain gauges in the region. Cork Airport recorded 51.2 mm for the 24 h period ending midnight on Thursday. Roche’s Point at the mouth of Cork harbour recorded 37.2 mm. Sherkin Island in West Cork recorded 39.8 mm. It is difficult to believe that over 100 mm of rain fell in the Lee Valley on the same day – within a few hours!
In the “River Lee flood of November 2000” report, table 4.1 shows the rainfall recorded at six rain gauges in the week leading up to the flood averaging 128 mm for the week – with a maximum of 140 mm at one of the gauges. Unfortunately these rain gauge data are not available on the internet.
Dear ESB, please disclose your rain gauge data for the 6 gauges in question for the 7 days to midnight on Thursday.
If one looks at figure 5.2 in the same report, there is a chart showing the recorded water levels, discharge and inflow in the Nov 2000 flood, as well as the rainfall. I would like to see a similar chart published for the ten day period to 21.11.2009. Looking at the chart traces in the 2000 event it is clear that the ESB personnel were asleep at the wheel in terms of water level management. While the reservoir level starts rising rapidly from the evening of 26.11.2000, they don’t start to increase the discharge (from 100 to 150 m3/sec) until half-way through the 28th – despite the continuously heavy rainfall. It is only after the inflow spikes (almost a day after the spike) that the discharge is increased from 150 to 275 m3/sec. The discharges should have been running at a rate of at least 200 m3/sec continuously (outside high tide peaks) from early on the 26th.
The safe water level should be set at something less than 48 mOD (to use their antiquated measurement system), and water level gauges should be installed at critical points downstream along the river, to report in real-time back to the control system in Inniscarra when downstream river levels are reaching critical levels.
Met Éireann’s presentation of weather information could also be improved on their website. It is a false economy to restrict or dumb down the quality and availability of weather information when one considers the massive cost of this single flooding event.
While they have a three-hour forecast which shows anticipated rainfall in detail in each part of the country, they need similar levels of detail covering the next 6, 12, 18, 24, 30 and 36 hours. The Spanish meteo service offer this service for wind, precipitation, temperature and other information, using the same HIRLAM model as is used by Met Éireann. The detailed forecast numbers from HIRLAM should also be published in text files to enable anybody interested (local authorities, utilities, householders, farmers etc) run an Excel spreadsheet to automatically pick up the data of interest to them over their internet connection. This would allow people to make calculations and build their own mathematical models to enable them to minimise the risks to their business, community or household.
Detailed access to good weather forecasting is essential for efficient energy use - whether you run a wind farm, have solar panels, or store heat in one form or another as part of your energy management system.
This event should be a wake-up call to everybody. Extreme weather events have to be intelligently managed for using the best available information.
Report on the 2000 flood referred to above:
https://sites.google.com/site/probeinfosite/docs/floodreportleevalley2000.pdf?attredirects=0&d=1
HIRLAM forecast Spain showing detailed rainfall and other projections up to 48 hours in advance:
http://www2.aemet.es/web/infmet/modnum/hirlam.html
(click on 00 or 12, Superficie, and H+06 and Precipitation etc to reveal map)
The Spanish site measures rainfall in l/m2 (litres per square meter).
1 mm of rain falling on the ground = 1 litre of water per square meter
1 tonne of water = 1 m3 (cubic meter) = 1,000 litres
Some journos resort to imperial measurements to dumb things down and confuse even more:
4 imperial inches of rain = more or less 100 mm = 100 litres of water per m2You are missing the point! I'm saying take the max allowed level 2m lower, and this will give you the spare capacity in time to search for bodies and other emergencies as well as deal with extreme rainfall.
The existing regulations governing water levels are obviously not working - hence the floods and panic discharges.
The Iniscarra dam (along with Ardnacrusha) are part of Ireland's aging, neglected infrastructure. Reducing levels by 2 m lightens the pressure load on the system by 28 million tonnes. It is grossly irresponsible to continue with the status quo.You are confusing two issues. The floods in the streets of Cork in the 19th century were a function of the low level of the streets in high tide conditions. High tide came in (eg spring tide), streets got flooded, and water came up drains (because the drains dumped water into the river directly). That flooding could happen in a drought year, when the Lee Valley had low levels of water.
This thread is about the ESB dams and their contribution to flooding.
I highlited the bits that I think are in fact quite liablious! You're making a lot of assumptions here, and think you;re completely right. You seem to think people make decisions on weather to let water out on a whim. I like the dig at the ageing infrastructure, as if there's a problem with the dam, and it can only hold back a restricted amount of water.I'm not arguing that the dam held back NO WATER. My simple argument is that more reserve for emergencies should be kept available all the time with a new normal max water height. This would allow discharges to be managed rather than having to take place in a "panic".
The flow rate of the Bride is in sec. 5.4 of the report I linked to in my root posting -
https://sites.google.com/site/probeinfosite/docs/floodreportleevalley2000.pdf?attredirects=0&d=1. The precise number quoted is 53 tonnes/sec on 21.10.1988.
It is a matter of priorities - do you want to extract every last kWh of electricity from this system (which is small anyway in the context of Ireland's current needs in 2009) - at a phenomenal cost in terms of insurance claims, inconvenience and no water in people's taps for over a week?
The insurance claims total for this one event would probably buy over 200 MW of wind turbine capacity - which capacity would last for about 25 years. It is a no-brainer!0 -
I highlited the bits that I think are in fact quite liablious! You're making a lot of assumptions here, and think you;re completely right. You seem to think people make decisions on weather to let water out on a whim. I like the dig at the ageing infrastructure, as if there's a problem with the dam, and it can only hold back a restricted amount of water.
I'm just quoting from facts - many / most of which come from ESBI's own reports and Met Eireann data.
I don't think people make decisions on dam discharges "on a whim". I have no doubt that these people are responsible and conscientious. Unfortunately they are working within a "system" which appears to me to be asleep on occasions. The system involves multiple public agencies within and without the ESB. And yes, I do have reservations about how proactive people were (as I have already referred to) when I examined figure 5.2 in the 2000 flood report.
I am attempting to highlight the need for a fresh look at the system and what the priorities should be in 2009 - some fifty years after these projects were first built.
As for aging infrastructure - how long do you think the dam will last? A thousand years? It has a safe life cycle - and I am no expert in the longevity of dams or the quality of the engineering that went into this project. It appears to me to be prudent to reduce the stresses put on the structure as it ages - and this fits in with the idea of lower maximum permitted water levels.
The proof of the pudding is in the eating. The intensity of flooding that we have witnessed would not have taken place if there was more spare capacity available in the system.0 -
They have a “bowl” with a capacity of only 35 million tonnes of water (ie the two river Lee reservoirs) – which is obviously very “cone shaped” given the small capacity for a reservoir system with a surface area of 14 km2.
The sustainable discharge rate of this bowl is apparently around 150 tonnes per second (into the River Lee downstream into the city). It is unclear from the item if this discharge rate makes provision for the potential discharges from downstream tributaries (ie rivers not controlled by the dam system). Let’s assume for a moment that it does.
The rainfall on Thursday week was at 800 tonnes per second – (the ESB’s own calculations indicate that it could be over 1300 tonnes per second on a really bad day –[see the 2000 flood report]).
The bowl was therefore filling at 650 tonnes per second, net, (800 inflow - 150 discharge), assuming nothing was done to increase discharge rates to panic levels which could lead to flooding.
This implies that if the bowl was empty at the start of an extreme downpour, the Lee reservoir system could hold out for just 15 hours at this level of rainfall, before discharges into the city river system, would lead to a risk of flooding. I repeat, fifteen hours of heavy rain would fill the system from empty!!!
Logically, if the reservoir was 2/3 full before a deluge at 800 tonnes/sec, the system could hold out for about five hours.
This allows very little time for emergencies on top of deluges – such as searches for bodies, etc.
One can only conclude in my view that anything more than perhaps half-full as being the new normal maximum permitted level is leaving too much to chance. The reservoir is far too small given the rain gathering potential of the 1,100 km2 catchment area that feeds it.
One might adjust the maximum permitted level based on historical rainfall levels in the area for each month of the year. Statistically the wet months (based on Cork Airport statistics) are October to March – so one might have a higher maximum permitted level during the dryer months of April to September – which would help increase the summer hydro generation kWh potential with minimal statistical additional flood risk. The statistics for the six rainfall gauges in the river valley should be used rather than Cork Airport data. This number might also be fine tuned by monitoring the projected rainfall over a rolling 10 day forecast period based on the ecmwf.int medium term forecast, and the Met Eireann soil moisture deficit data for the catchment area*.
The risk of a 1,300 tonne per second one in 10,000 year inflow must also be considered in deciding on new maximum limits.
In terms of electricity generation capacity (27 MW) it makes a tiny contribution to the national requirements. About the same as 7 modern wind turbines. To put it in context, total hourly electricity demand in IRL is typically between 3,000 and 5,000 MW.
The plant has been in place since 1953 and has more than paid for itself financially. The insurance risk / cost of keeping the system running with anything like a full reservoir greatly exceed the value of the electricity produced.
Perhaps it is time for it to go into “semi-retirement”, and change the dam’s prime focus to that of a “buffer" system protecting the city and region from increasingly extreme weather conditions?
A similar philosophy should be applied to the Shannon and Liffey systems.
One additional consideration when it comes to the Liffey system is the provision of adequate storage for the city’s water supply – and the adequacy of the size of the reservoir system needs to be considered in the context of any reduction levels to create an increase buffer. Introducing higher maximum permitted reservoir levels for dryer months (as proposed above) would help in terms of matching water demand with supply.
Related issues regarding water supply apply on the River Lee. The extraction/purification plant on the Lee Road (responsible for about 40% of Cork city’s supply) is old and is only a few metres above the level of the river (in an area not dissimilar to Strawberry Beds in Dublin). It would be very easy to acquire a suitable site at a higher altitude along the river valley to build a modern replacement plant. The water storage reservoir in Shanakiel (Sunday’s Well) is too small and too low to provide continuity of supply to hilly areas of the city for any sustained period of time in the event of plant failure. Reports indicate that taps were dry in many households shortly after the water works was flooded. An additional, large capacity reservoir at a higher altitude is required.
Climate change, seasonal tides, murphy’s law, compound themselves... which is quite frightening in the context of the limited control they have over discharge rates downstream during emergencies. It is time to stop leaving maximum reservoir levels at historic levels which is leaving too much to chance. While any country will experience the odd flood, it is only third world countries that have to put up with continuous flooding events, decade in, decade out.
*http://www.met.ie/climate/agri-meteo-data.asp
*http://www.met.ie/agmet/smd_pds.asp (-10 = saturated soil)
http://www.irishtimes.com/newspaper/ireland/2009/1128/1224259620533.html0 -
A few further thoughts:
1. The ESB’s historic high maximum water level limits for dams and lakes that feed hydro power plants need now to take account of all the badly planned buildings that have been constructed on flood planes over the past few years.
While the ESB can’t be held accountable for bad planning decisions (though they could of course have objected to planning applications if they were monitoring the issue pro-actively over the past decade), the flood planes that ESB formerly used to avail of to take emergency overflows during extended periods of heavy rainfall no longer exist in many cases. The recent flooding in Sallins is a case in point. A heavy downpour in the Dublin/Wicklow mountains and people were washed out of their homes/apartments in Kildare a few hours later. There is no natural slack in the system anymore, downstream of the reservoir/lake to deal with problems without causing large scale damage to property in many cases. The ESB must adjust its systems, internal controls and procedures to deal with this new reality.
The slack that used to be in the river banks and flood planes will have to be replaced by a significant lowering of reservoir and lake levels so that river discharges can be safely restricted during periods of heavy prolonged rainfall.
2. With all due respect to the proxy for the ESB (apparently an ex ESBI person) who appeared on The Frontline TV programme recently, a drastic permanent lowering of lake and reservoir maximum water levels will greatly reduce the flood risk in the Liffey, Lee and Shannon catchment areas, because it will allow dam controlled river flows to be brought to a near halt (reduced to the maximum safe discharge capacity of the river system downstream) during crisis events. The logic should be obvious. Of course one wouldn’t expect anybody with any connection with the ESB to ever admit that a lowering of reservoir/lake levels would reduce flood risk, because to say so would be an admission of liability by the company. Imagine him on the witness stand in an insurance industry –v- ESB court case for flood losses after making a statement of this nature on TV!
The ESB didn’t have the moral fibre to put up an official spokesperson on Pat Kenny’s programme. Something to hide... Lots to hide.... Millions of tonnes of water...
3. One wonders if the ESB has accurately defined the geographic co-ordinates of the catchment areas of the three river systems, given the arguments between ESB and Met Eireann? While weather forecasting is a last resort and something to feed extreme weather warning systems to give people notice to take emergency action, such warnings need to be based on precise data. Is the ESB rainfall gauge data fed into the Met Eireann system (to improve the accuracy of weather forecasts for the zone) or does the ESB hoard these data to itself? The higher the resolution of the data fed into the weather model, the better the quality of the forecast.
The Board of Directors of the ESB is accountable for these matters, and the onus is on them to put the systems in place to fix the flooding problems arising directly or indirectly as a result their hydro generation systems.
http://www.rte.ie/news/thefrontline/
http://www.rte.ie/news/2009/1201/weather_av.html?2659135,null,2090 -
Your forgetting one huge factor.
The Lee catchment area!
Re calculate your figures for this and flow rates.
Your left with two options.
1 Release the water flooding the city below the dam
2 Hold the water and dont release any more than normal. This results in a build up behind the dam. The land behind the dam floods. Then the dam comes under pressure as the water level behind it rises. The water tops the dam flooding the city down stream anyway or far worse the dam fails releasing all its water in one go and the city is washed away no more.
Its that simple.
You can only release water that is there at the dam not water thats on the way0 -
During how many hours over the six days, weeks, months prior to last Thursday week’s flood has there been no water at the dam? I suspect the answer is zero hours. Because the ESB was busy hoarding water – except when the ****** hit the fan, and they went on a maxxx effort job to dump as much water on the city as possible, because they had no alternative.Your forgetting one huge factor.
The Lee catchment area!
Re calculate your figures for this and flow rates.
Your left with two options.
1 Release the water flooding the city below the dam
2 Hold the water and dont release any more than normal. This results in a build up behind the dam. The land behind the dam floods. Then the dam comes under pressure as the water level behind it rises. The water tops the dam flooding the city down stream anyway or far worse the dam fails releasing all its water in one go and the city is washed away no more.
Its that simple.
You can only release water that is there at the dam not water thats on the way
They said there was 800 tonnes of inflow/sec for about four hours last Thursday week. This would require about 11.5 million tonnes of storage capacity to accommodate, and if the risk management system was functioning properly, this capacity would have been available.
The ESB has 6 rainfall gauges, and presumably retain the data from these over the years. It is easy to calculate if they could not deal with last Thursday weeks deluge even with while maintaining a “zero water level policy” in the reservoirs. If they couldn’t, they have an obligation to say so publicly, so that government, companies and the population generally can consider their options.
I have come across an OPW document on the water storage capacity of the Liffey system at Blessington Lake. I shall post this in a separate item shortly. The Blessington lake can store six months flow of the Liffey. With all this storage capacity on hand, they had floods in Sallins and other parts of Kildare as well as Strawberry Beds, after a blast of rain on the Dublin and Wicklow mountains the other day. One has to ask why? It seems to me that the control and risk management systems were not working efficiently to protect people and property situated in KE/D.
Same problem as on the Lee a week earlier, and in the River Shannon catchment area.0 -
While the river Lee reservoirs are under pressure to store 6 days or sometimes 6 hours of catchment rainfall, the Blessington / Pollaphuca system can apparently store SIX MONTHS of catchment area rainfall without overflowing.... As a result, an OPW document reports that the “plan B” flood prevention dam spillway at Pollaphuca has never had to be used in its 60 year history.... (Sec 1.1*)
It begs the question why the Liffey was allowed to overflow at Sallins and Strawberry Beds the other day...
Is there adequate downstream river level monitoring with real-time feedback into a control system that automatically shuts down dam discharges to prevent flooding along the Liffey? There is no excuse for river floods when you have six months storage capacity upstream, and a dam to shut down the flow......
Flooding is akin to road traffic jams in my mind. Many urban areas in Ireland have appalling traffic light control algorithms, and are badly designed (eg lights remaining green when there are no cars coming from a side road, the use of time wasting non-conflicting pedestrian crossing phases, [conflicting pedestrian crossing phases work very well in continental European cities, typically adding 25% to traffic carrying capacity while improving pedestrian safety]). These traffic signalling inefficiencies in Ireland reduce the traffic carrying capacity of junctions, creating needless traffic delays, waste of fuel and peoples’ time etc.
River flood prevention systems need to be automated like traffic lights, to reduce the risk of human error, using systems that feed accurate real-time data on river levels at several high risk points along the course of the river, so that immediate action is automatically taken to reduce/stop the river flow before peoples’ property gets flooded. The financial payback from this type of investment would be very large over a short period of time when one takes into account the financial cost of flood damage.
Some areas along the Mediterranean have to deal with rainfall levels of 800 mm in one day, on occasions. Perennially wet Ireland has problems dealing with 100 mm!
*http://www.opw.ie/hydrology/data/speeches/National%20Hydrology%20Seminar%202001%20No%209%20-%20FLOOD%20RISK%20MANAGEMENT%20-%20STORAGE.pdf0 -
QUOTE 'They said there was 800 tonnes of inflow/sec for about four hours last Thursday week. This would require about 11.5 million tonnes of storage capacity to accommodate, and if the risk management system was functioning properly, this capacity would have been available.'
Great if it only rained that much for four hours pity that didnt happen cause it rained for days and days! Not just four hours in one spot. Case in point, alot of the water that fell two weeks ago is only reaching limerick city now! You would needs billions of spare capacity to have full risk redundancy.
I dont know much about the other areas that were flooded. Lots of places were for lots pf different reasons. Places that havnt been flooded in living memory because of the sheer volume of water that fell as rain! And its impossible to predict where water will end up and how much of it there will be.
Of course there should be a risk management system operated by the councils and planners.
Salins was a case of them building in a area that was know to flood!!!!!!!!!!!
Planning is not very well understood in this country, just look at the **** thrown up over the last decade!!!!!!!!!!!!!!!!
Buyer beware!0 -
QUOTE 'They said there was 800 tonnes of inflow/sec for about four hours last Thursday week. This would require about 11.5 million tonnes of storage capacity to accommodate, and if the risk management system was functioning properly, this capacity would have been available.'
Great if it only rained that much for four hours pity that didnt happen cause it rained for days and days! Not just four hours in one spot. Case in point, alot of the water that fell two weeks ago is only reaching limerick city now! You would needs billions of spare capacity to have full risk redundancy.
Fine. Disclose the actual rainfall numbers in the Lee catchment area from the rain gauges over the past six months or whatever period you like that shows that even with a zero water level policy in the reservoirs, the flooding would have taken place. Based on a flood free discharge rate of 150 tonnes per second or whatever number the ESB can live with. Hard numbers please!
The ESB has responsibility for the Lee system. The ESB should have the risk control systems in place. The ESB has the control over the sluce gates - not councils and planners.Of course there should be a risk management system operated by the councils and planners.
Why was it known to flood? (a) because it is a weak point along the Liffey, prone to flooding if the ESB throws too much water down the river or (b) because of direct rainfall on the Sallins area? If you can show (b) to be the case, the ESB is off the hook on this particular event.Salins was a case of them building in a area that was know to flood!!!!!!!!!!!
There is very little new construction in Strawberry Beds. Why was that flooded. Was the river Liffey not coming up to the R109? If so, the discharge into the Liffey should have been reduced automatically, based on river level detectors located at low points along this route.
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=strawberry+beds,+ie&sll=37.0625,-95.677068&sspn=53.564699,135.263672&ie=UTF8&hq=&hnear=Strawberry+Beds,+County+Fingal,+Republic+of+Ireland&ll=53.365432,-6.400588&spn=0.009962,0.033023&t=h&z=16
I agree, planning was a total mess. And the ESB has to live with this reality and cut its cloth (or control its rivers) accordingly. The new reality for the ESB. The company can't adopt a "close your eyes and drive on as before" attitude.Planning is not very well understood in this country, just look at the **** thrown up over the last decade!!!!!!!!!!!!!!!!
Buyer beware!0 -
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But the problem is its not only the ESBs fault. TBH your just ESB bashing. The goverment, councils and planners all approved the construction of the dams.
The ESB are in a hard spot and you need to appreciate this. And they need to investigate this incident.0
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