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Shannon river basin flooding and the ESB

  • 27-11-2009 10:07am
    #1
    Closed Accounts Posts: 2,055 ✭✭✭


    I’ve been reading the report on the Shannon flood of December 1999 – early 2000.

    The water draining out of the Shannon River system is constrained at Parteen / Ardnacrusha, where the ESB operates a “tap” (a weir / sluce gates) to restrict the flow. Effectively, the ESB appears to be using the Shannon lake system (Lough Derg upstream to Lough Allen + the river itself and its tributaries) as a reservoir to store water for the Ardnacrusha hydro generation system!

    The design of the Ardnacrusha system appears to be inefficient from an electricity generation perspective, because less than half the water flowing down the Shannon at that point is routed via the generation turbines. They created a canal to take water off the main Shannon to feed the turbines. In any other country, I would have thought that the canal would be created to carry boats through a system of locks to conserve water, and they would put the hydro turbines on the main river, capturing the considerable energy in Ireland’s largest river flow.

    I’ve read many reports on the current flooding problem in the Shannon river basin affecting numerous areas – Athlone, Banagher, Ballinasloe and numerous other communities, basically from the Border down including parts or most of counties Leitrim, Roscommon, Westmeath, Galway, Mayo, Offaly, Tipperary, Clare and Limerick are at risk.

    Aside from Limerick, these areas are in the reverse situation of Cork city last week – because they are upstream of the ESB dam (whereas Cork is downstream), and their farms, towns and villages are unwittingly becoming part of the reservoir system due to bad medium and long term water level management by the ESB at the Ardnacrusha/Parteen system.

    The solution to the problem is partially the same as for Cork*, enforce a “new normal” where maximum permitted water levels in the lake and river system are reduced by a figure of 1, 2 or 3 meters or whatever it takes to create spare capacity in the lakes to deal with prolonged periods of heavy rain. The quantities of water to be managed are enormous – 1,035 tonnes a second fell on the Shannon catchment on 27.1.1995. The maximum discharge rate through the Ardnacrusha /Parteen system is 700 tonnes per second. This implies that the Shannon system has to be kept low enough in terms of water level to be able to store a 300 tonnes per second build-up of water over a prolonged period of rainfall.

    Lough Allen, Ree and Derg have a total surface area of 262 km2. For every 1 m reduction in maximum permitted water levels in these three lakes, one would buy 10 days of storage capacity for torrential rain pouring 24 hours each day at 300 tonnes per second faster than the existing Ardnacrusha / Parteen system could discharge.

    Deciding the level of reduction is more complex compared with the River Lee, because of the numerous lakes and tributaries and intermediary sluce gate systems which form this massive reservoir. To cater for new normal increased rainfall peaks, it may be necessary to widen and deepen the Shannon between Killaloe and Limerick city. Looking at the satellite imagery there are numerous islands of trees in the river around Castletroy and Castleconnell which may be inhibiting peak flow rates.

    The decision and implementation of the decision to reduce the maximum permitted water levels in the lakes is urgently required to minimise the risk of a repeat of the flooding. Other measures will obviously take time to engineer and implement. The cost of a water level reduction is minimal.

    There is no excuse for inaction on this front.... it has been a problem for decades.


    *http://www.boards.ie/vbulletin/showthread.php?t=2055751080

    Report on Shannon flood of 1999-2000: https://sites.google.com/site/probeinfosite/docs/shannonfloodreport19992000.pdf?attredirects=0&d=1

    Picture of Parteen weir: http://www.flickr.com/photos/m_j_g/106333779/in/photostream/


Comments

  • Registered Users, Registered Users 2 Posts: 24,537 ✭✭✭✭Cookie_Monster


    probe wrote: »
    The design of the Ardnacrusha system appears to be inefficient from an electricity generation perspective, because less than half the water flowing down the Shannon at that point is routed via the generation turbines.

    At the time they built it, it was revolutionary and one of the largest construction projects in the world. Also supplied some crazy %age of the nations power, something like 90-95% iirc


  • Closed Accounts Posts: 2,055 ✭✭✭probe


    An interesting document I came across on the River Shannon corridor, by way of general information on the area:

    http://www.heritagecouncil.ie/fileadmin/user_upload/Publications/Inland_Waterways/WCS2006/2006_WCS_Study.pdf


  • Registered Users, Registered Users 2 Posts: 78,580 ✭✭✭✭Victor


    The ESB can only really control Lough Derg, about 30m OD. Changing the level in Lough Derg isn't going to affect Lough Ree at 35m OD or Lough Allen at 47m OD.


  • Closed Accounts Posts: 2,055 ✭✭✭probe


    Victor wrote: »
    The ESB can only really control Lough Derg, about 30m OD. Changing the level in Lough Derg isn't going to affect Lough Ree at 35m OD or Lough Allen at 47m OD.

    If you lower the maximum water levels in the upstream lakes, given the system of sluce gates in place, this will give you additional storage capacity to deal with high intensity rainfall events. As far as I can see there are multiple public agencies involved in water levels on the Shannon - including the ESB.

    The higher level lakes are going to flow into Lough Derg - and this must be managed in a co-ordinated fashion. A single decision maker is required for the entire river system to take overall responsibility.


  • Registered Users, Registered Users 2 Posts: 2,834 ✭✭✭air


    I'd imagine that the reason they aren't fully exploiting the full potential of the river is on environmental grounds. The "inefficient" stretch of river between Killaloe and Limerick which you want to "deepen" and "widen" is an important salmon spawning ground and the ESB have a fisheries hatchery in the area also.
    The area is so sensitive in fact that UL had planning difficulties getting permission to put a new bridge across the shannon in Castletroy due to the effect it would have on the riverbed.

    Your point in any case is completely lost because Parteen Weir can discharge water from Lough Derg faster than it can exit Lough Derg due to the width of the channel at Killaloe. Ergo the ESB's control of water levels on Lough Derg would have little or no impact on flood conditions upstream.

    I for one are glad that the ESB didn't do a job on the Shannon like the Chinese did with the Yangtze river.


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  • Registered Users, Registered Users 2 Posts: 32,370 ✭✭✭✭Son Of A Vidic


    Ireland and forward planning don't mix really, we are a reactionary nation not a proactive one. If there was a world 'Finger Pointing' and a 'Blame Game' world championship, we would just have it sown up:(


  • Closed Accounts Posts: 2 gbn


    probe wrote: »
    I’ve been reading the report on the Shannon flood of December 1999 – early 2000.

    I must take serious issue with you on this post its old IFA/farmers claptrap, that has been bebunked both professionally and by informed observation.
    The water draining out of the Shannon River system is constrained at Parteen / Ardnacrusha, where the ESB operates a “tap” (a weir / sluce gates) to restrict the flow. Effectively, the ESB appears to be using the Shannon lake system (Lough Derg upstream to Lough Allen + the river itself and its tributaries) as a reservoir to store water for the Ardnacrusha hydro generation system!
    no thats a simplistic description, The primary restriction on the flow is the natural geography of the river sections, shallow and flat. coupled with some restrictions due to river crossings like athlone banagher etc. the lakes respond to the flow in and out and go up and down as that varies, they dont in general restrict the river flow in normal or flood conditions.

    Lets also debunk the ESB/storage system. The ESB made a policy decision in the 90's that ardnacrusha was no longer of any significant strategic importance as it now contributes less then 5% of irelans total electricity generation. They do not "store" water for electricity generation, they merely use whatever flow rate is available and generate accordingly, running one two three or four turbines are the rate allows. This is completely evident in summer months. water is not held back. The ESB controls Parteen weir, Athlone and Lough Allen sluices, all others are controlled by Waterways Ireland. The ESB did agree to reduce the wide variations of levels in Lough Allen to facilitate boating, but the effect is minimal.
    The design of the Ardnacrusha system appears to be inefficient from an electricity generation perspective, because less than half the water flowing down the Shannon at that point is routed via the generation turbines. They created a canal to take water off the main Shannon to feed the turbines. In any other country, I would have thought that the canal would be created to carry boats through a system of locks to conserve water, and they would put the hydro turbines on the main river, capturing the considerable energy in Ireland’s largest river flow.
    this is the most incredably uniformed statement I have ever read. The shannon hydroelectric system was designed to take a average of what the river generates . in summer flows, there is actually hardly enough water to spin even one turbine and lots of the time the turbines arnt running at all., a minimum flow is always maintained over parteen weir to maintain the downstream river ecosystem, hence the station can be starved of water. IN winter, the characteristics of the river basin is that far too much water is available in flood times, it would have made no economic sense whatever to build a monster 10-12 turbine system , merely on the off chance that the flow might be available.

    Also you are wrong in your understanding of the purpose of the head race ( the so called canal you mention). The head race is designed to smooth and control the flow of water to the turbines and secondly to maximise the height of water as the land drops away quickly here at its not possible to expand the lake to the power station directly. putting the station at the original end of teh lake at killaloe, would have lost valuable height and hence energy. This feature is extremely common in the siemens designs of the time.

    by the way the headrace is also a canal carrying boats through two locks (to conservse water) so its there despite your critism of its non-existence, perhaps a visit to the station and a chat to the engineers might inform you rather then listening to IFA nonsense.

    I’ve read many reports on the current flooding problem in the Shannon river basin affecting numerous areas – Athlone, Banagher, Ballinasloe and numerous other communities, basically from the Border down including parts or most of counties Leitrim, Roscommon, Westmeath, Galway, Mayo, Offaly, Tipperary, Clare and Limerick are at risk.

    Aside from Limerick, these areas are in the reverse situation of Cork city last week – because they are upstream of the ESB dam (whereas Cork is downstream), and their farms, towns and villages are unwittingly becoming part of the reservoir system due to bad medium and long term water level management by the ESB at the Ardnacrusha/Parteen system.

    name or produce these "many" reports, they dont exist, are they by recognised exports, the only comprehensive report was done in the fifties by a US army core of engineer with experience of US levies along the missisippi. he debunked the lower the levels issue and suggested that any engineering work to expand the capacity of the river would require expenditure on a truely enormous level that couldnt be justified, and his only possible suggestion was to reverse the River suck, and drain it to the western seaboard to act as an additional exit point. The ESB does not "hold water back", if fact in dry summers the lake levels have fallen considerably, theres noboby closing sluices to raise the levels
    The solution to the problem is partially the same as for Cork*, enforce a “new normal” where maximum permitted water levels in the lake and river system are reduced by a figure of 1, 2 or 3 meters or whatever it takes to create spare capacity in the lakes to deal with prolonged periods of heavy rain.
    No hydrologist agrees with you, this is the claptrap IFA nonsense that spouted by people who would like to grap the land so revealed by lowering the lakes. All professional opinion debunks the IFA "drain the shannon" nonsense.


    not to mention the enormous environmental damage that would be done to the surrounding wetlands, massive loss of habitat, etc. of course farmers are the worst offenders when its comes to protecting habitat. this leaves aside the visual damage to places like athlone where the lowering would turn the river into a trickle in dry summers. and explain how you would lower say LOugh Ree by 2 metres given that the weir is 4 feet , youd have to remove the river bed all the way from athlone to banagher.- nonsense, rubbish

    The quantities of water to be managed are enormous – 1,035 tonnes a second fell on the Shannon catchment on 27.1.1995. The maximum discharge rate through the Ardnacrusha /Parteen system is 700 tonnes per second. This implies that the Shannon system has to be kept low enough in terms of water level to be able to store a 300 tonnes per second build-up of water over a prolonged period of rainfall.

    Lough Allen, Ree and Derg have a total surface area of 262 km2. For every 1 m reduction in maximum permitted water levels in these three lakes, one would buy 10 days of storage capacity for torrential rain pouring 24 hours each day at 300 tonnes per second faster than the existing Ardnacrusha / Parteen system could discharge.
    theres a simple flaw in this logic and it has been pointed out many times, you can only lower a lake if you can get the water OUT OF IT. The situation that occurred in december was not caused soley by december rainfall. it was caused by the whole summers worth. the fact is that all summer the lakes were rising , especially lough Ree, By late august the levels were approaching winter levels, the water simply could not be got down the river fast enough. No body was "HOLDING BACK" water , how could they , it was over the sluice gates, ardnacrusha was running 4 turbines almost the whole summer and still discharging over parteen weir. Ree rose 4 feet over the normal summer levels.

    The simple fact is that downstream river sections are incapable of handling significant increased flows due to the flat gradient and shallow nature, their solution is to spread widthways and take the strain thatways, tahts what the creator intended.

    again consider what happened this year , a wet summer ( following a wet winter ) had meant that the systems was already approaching winter conditions at the end of the summer. All sluices were open, yet the levels still went up.

    When the increased rainfall appeared, it merely further over whelemed an already swollen system, your mythical 10 days of storage was long since used up by late august, then youd need another 10 or maybe 20 days storage to cope with teh demember rains. Not possible

    Look at where most of the flooding was generated, Around the major lakes NO, there was little additional flooding around most of lough Allen, Ree and Derg ( and I know this river extremely well). ( and where it did happen was a direct result of bad planning. Most of the flodding occured in the slow river sections, namely around Carrick, below the lock in AThlone and Banagher /ballinasloe. Firstly even with the floods we had the lakes remained "below" these river levels, hence they were not a serious restriction on them. Its the river geometry in these sections that causes problem, flat shallow, constricted by towns. ( and other housing and planning horrors). The level in the Lakes had no real effect on the flooding on the river sections. The levels dropped in these sections when the input flow into these sections went below the output sections. The level of the Lakes is and always basically irrelevant.

    Deciding the level of reduction is more complex compared with the River Lee, because of the numerous lakes and tributaries and intermediary sluce gate systems which form this massive reservoir. To cater for new normal increased rainfall peaks, it may be necessary to widen and deepen the Shannon between Killaloe and Limerick city. Looking at the satellite imagery there are numerous islands of trees in the river around Castletroy and Castleconnell which may be inhibiting peak flow rates.
    absolute balderdash, the fact is that even with a massive engineering program in the lower shannon, and the river bed here is all rock and very shallow in places, also massive works would be neccessary to reengineer the abbey river, the fact is this would do NOTHING to reduce upstream flooding especially the areas most vunerable , to Banagher to Athlone, remember Dedrg didnt rise above meelick weir, so was not constrsining this section, Ree would have to rise 9 metres to oppose drainage from the Carrick area, (I suspest Ree would flood Dublin first). Hence its levels have no effect on that flooding.

    THe simple fact is that as the fifties study show, unless you are preapred to effectively re-engineer the whole shannon, from the top to the bottom and effectively turn a wide slow moving flood prone river into a fast deep non flooding river that gets water quickly to the sea, you will not solve the problems by so called lowering of the lakes, (nor the othe IFA baby , the silt)

    This massive task would (a) bankrupt the country, (b) cause the riverside towns to be effectivly removed from thr planet and (c) reck untold environmental damage. and anyway cause the people who are currently flooded to be moved off their land anyway.

    The decision and implementation of the decision to reduce the maximum permitted water levels in the lakes is urgently required to minimise the risk of a repeat of the flooding. Other measures will obviously take time to engineer and implement. The cost of a water level reduction is minimal.
    no its not , johnn gormly does agree with you, all the hydrologists dont agree with you and significant lowering is not physically possible, nor is it hrdraulically possible in any sort of wet summer, ( This is proved this summer). lowering the lake only works in the case of a kind of flash fllood that appears in a couple of days and then stops, thats not what we get in this country, its sustained rain over a relatively long period, somtimes months.
    There is no excuse for inaction on this front.... it has been a problem for decades.
    your right about that , the farmers, the biggest vested interest in the whole area would love to reduce levels and remove flooding, they love to turn flood plains in development land and grap extra lakeshore land that would be revealed.

    The first thing thats need to be done is to accept that short of engineering on a massive scale, the shannon is what it has always been, a slow flat river feed by a very large catchment area, whose area can generate a lot of extra water in wet times.

    Secondly the only solution to this is to allow it access to its flood plains ,as far as it needs. Poor planing that let people build on this floodplains needs to be rectified, buy back the land and houses, resettle people and return the land to the river. completely halt all extended flood plain development.

    and finally lets ignorethe IFA claptrap and the "drain the shannon nonsense" and lets see it for what it is --greed.


    *http://www.boards.ie/vbulletin/showthread.php?t=2055751080

    Report on Shannon flood of 1999-2000: https://sites.google.com/site/probeinfosite/docs/shannonfloodreport19992000.pdf?attredirects=0&d=1

    Picture of Parteen weir: http://www.flickr.com/photos/m_j_g/106333779/in/photostream/[/quote]


  • Closed Accounts Posts: 7 HoolaHoops


    Hi, I'm looking at possibly moving to Castleconnell. It seems like a beautiful area but I'm worried that it lies on the Shannon flood plains and is liable to flooding.

    Could anyone advise me,

    1. Should this be a concern, should I buy here.
    2. if Castleconnell itself has any protection from floods along the Shannon.
    3. With all the talk of climate change are we entering an era of new record breaking river levels and subsequent flooding!

    The estate I'm looking at is Castlerock which is approx half a Km from the river.


  • Closed Accounts Posts: 2,055 ✭✭✭probe


    HoolaHoops wrote: »
    Hi, I'm looking at possibly moving to Castleconnell. It seems like a beautiful area but I'm worried that it lies on the Shannon flood plains and is liable to flooding.

    Could anyone advise me,

    1. Should this be a concern, should I buy here.
    2. if Castleconnell itself has any protection from floods along the Shannon.
    3. With all the talk of climate change are we entering an era of new record breaking river levels and subsequent flooding!

    The estate I'm looking at is Castlerock which is approx half a Km from the river.

    While I have no knowledge of the area, "go for the hills"... You need to get a place around 30m above normal river height. If the height differences are not obvious from the landscape, get a GPS with EGNOS (European Geostationary Navigation Overlay Service) and measure the altitude at river level, and at the level of your proposed abode. If you aren't at least 30 m above the river, I'd pass on the property. EGNOS increases the accuracy of GPS in Europe - and it is free.

    There are side issues - where your supplies will come from during a flood. Water - where does it come from (it could become undrinkable in flooding), shopping, electricity, and access etc - including getting to work, schools, hospitals, and telecommunications - will your internet/phone connection survive because it depends on kit that is under water etc. Can you get to/from the proposed location without going near river level? There may be other issues particular to your daily life which one might need to consider.


  • Closed Accounts Posts: 2 inco


    There is flooding every year on the Shannon.
    Every number of years, this event is significantly worse than most.
    On rare occasions it is considered disastrous, such as this latest one and 99/00.
    I think around '95 before that.
    Uproar ensues and the blame game starts, wacky ideas are proposed and committees are set up.
    A month or two passes, things dry up and it is all forgotten about, except of course by those who need new or repaired property.

    There is a set of rules called "Regulations for the control of the river shannon", that describe the procedure to be followed by the ESB in the course of utilizing the power of the Shannon to produce electricity.

    In the 99/00 event I can confirm that these rules were not followed.
    The decision to "spill" water from the weir into the old shannon, as per regulation, (which rests with the top management of the power station), was delayed by twenty four hours, despite the advise of the operators in Ardna who could foresee that the implications of holding back such a body of water even temporarily could be disastrous given the rapidly rising levels and inflows.
    The usual hullabaloo ensued.
    ESB rolled out their various spokesmen to explain that they had performed admirably, the management were seen on RTE travelling the Shannon on speedboats surveying the situation, "independant" experts were rolled out to confirm their prowess, a subdivision of ESB, ESBI produced a report to vindicate the mother company. Everyone else paid for it through their bills, as usual.
    These events are recorded, hour by hour, in the "Control room log" and "Hydrometric Log" that are kept by the control room staff in Ardnacrusha, including reference to calls being made to the management, advising of the necessity and looking for permission to "spill", as per regulations.
    In the aftermath a report was sent to the Office of Public Works describing the event. A "freedom of information" request was made to the OPW on my behalf looking to see a copy of this report, but was denied without explanation.
    The ESB cannot make a loss. If they have unusual expenses then your bill goes up to cover that, and still make a profit. They can therefore afford to make the most horrendous mistakes, and subsequently defend themselves to the hilt with the most expensive lawyers and all at your expense.
    And they can then have a nice little bonus for the top brass too, after all that.


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  • Registered Users, Registered Users 2 Posts: 15,443 ✭✭✭✭bonkey


    inco wrote: »
    In the 99/00 event I can confirm that these rules were not followed.
    The decision to "spill" water from the weir into the old shannon, as per regulation, (which rests with the top management of the power station), was delayed by twenty four hours, despite the advise of the operators in Ardna who could foresee that the implications of holding back such a body of water even temporarily could be disastrous given the rapidly rising levels and inflows.
    ...
    A "freedom of information" request was made to the OPW on my behalf looking to see a copy of this report, but was denied without explanation.
    Without trying to turn this into an ESB thread...

    how exactly can you confirm these things, when your request to see the evidence which would be required for such confirmation was denied?

    Also...just for clarification...when you refer to "the top management of the power station", who are you referring to? The station manager?


  • Moderators, Science, Health & Environment Moderators Posts: 6,376 Mod ✭✭✭✭Macha


    Off-topic posts deleted. If you suspect a poster of trolling, please use the report post button people - that's what it's there for.


  • Registered Users, Registered Users 2 Posts: 15,443 ✭✭✭✭bonkey


    probe wrote: »
    While I have no knowledge of the area, "go for the hills"... You need to get a place around 30m above normal river height.

    Why so much height, probe? If its purely to avoid flooding...then 30m seems excessive, unless Castleconnell has a habit of being entirely submerged (and then some) when the Shannon floods.

    Also....working from memory....isn't the land pretty flat around there? 30m is quite a height difference to be looking for on flat land.


  • Closed Accounts Posts: 2,055 ✭✭✭probe


    bonkey wrote: »
    Why so much height, probe? If its purely to avoid flooding...then 30m seems excessive, unless Castleconnell has a habit of being entirely submerged (and then some) when the Shannon floods.

    Also....working from memory....isn't the land pretty flat around there? 30m is quite a height difference to be looking for on flat land.

    You can't talk - you hang out some 444 m above sea level (in CH-3250)....

    Perhaps I'm being a tad conservative with 30m - but who knows what the tsunami ripple effect might be along the Shannon if Cumbre Vieja* (Canary Is) was to splash into the Atlantic?

    *http://en.wikipedia.org/wiki/Cumbre_Vieja


  • Registered Users, Registered Users 2 Posts: 15,443 ✭✭✭✭bonkey


    You based your 30m above river level on a fear of what might happen if the Canary Island faultline gave way?

    Gosh.


  • Closed Accounts Posts: 2,055 ✭✭✭probe


    bonkey wrote: »
    You based your 30m above river level on a fear of what might happen if the Canary Island faultline gave way?

    I suspect that nobody who lives in Cork city at alt 30m+ had flood problems in their home during the ESB floods in November last year (aside from their water being cut off, because a water purification plant that serves nearly half the city is situated about 1 m above river level).

    The thing on the Canary Islands is a big chunk of rock / landslide risk, probably around 500 km3 of stuff, perilously perched, and which could be dumped into the Atlantic by a quake or other energy force of similar magnitude. Even if it is only a 10m wave by the time it reaches IRL, one would wonder what the hydro dynamics would be in the Shannon Estuary. The "splash" could be a lot higher than 10m.

    The last think probe wants is HoolaHoops posting a complaint here in x years time that he was flooded out in his new house. He will also have a far better view if he can find a place in the 30m alt range. Something CH-residents will be more familiar with than most...

    http://www.tsunami-alarm-system.com/uploads/pics/la_palma_erdrutsch_tsunami_01.jpg


  • Closed Accounts Posts: 2 inco


    how exactly can you confirm these things, when your request to see the evidence which would be required for such confirmation was denied?

    Also...just for clarification...when you refer to "the top management of the power station", who are you referring to? The station manager?

    Sorry was asleep on this one.
    I can confirm because I was there.
    The "evidence" is in the "control room log" and "hydrometric log sheets" and "regulations book" as stated. My request to the OPW was an attempt to see what "spin" was put on that report, not an attempt to gather evidence re the actual event, more so, the aftermath of the event.
    Top management at that time would have been the Station manager and the Civil Engineer, both comfortably retired now.
    There have been changes since with a lot of the control transferred to a remote station, Turlough Hill. But some staff remain in the control room in Ardna, thumb twiddling till retirement.


  • Registered Users, Registered Users 2 Posts: 15,443 ✭✭✭✭bonkey


    probe wrote: »
    I suspect that nobody who lives in Cork city at alt 30m+ had flood problems in their home during the ESB floods in November last year (aside from their water being cut off, because a water purification plant that serves nearly half the city is situated about 1 m above river level).

    I would equally suspect that no-one who lives at 10m+ had problems, nor even those at 5m+.

    The thing on the Canary Islands is a big chunk of rock / landslide risk, probably around 500 km3 of stuff, perilously perched, and which could be dumped into the Atlantic by a quake or other energy force of similar magnitude. Even if it is only a 10m wave by the time it reaches IRL, one would wonder what the hydro dynamics would be in the Shannon Estuary. The "splash" could be a lot higher than 10m.

    The last think probe wants is HoolaHoops posting a complaint here in x years time that he was flooded out in his new house. He will also have a far better view if he can find a place in the 30m alt range. Something CH-residents will be more familiar with than most...

    http://www.tsunami-alarm-system.com/uploads/pics/la_palma_erdrutsch_tsunami_01.jpg

    The reason I was surprised is that you didn't bother pointing out that your advice wasn't based on the frequent, or even infrequent flooding events that will happen in the lifetime of someone living in any given location, but rather on a possible "doomsday" scenario that may or may nor occur sometime in the next epoch...and even then it seems that your 30m is based on an "I have no idea of what the effects might be" guess.


  • Closed Accounts Posts: 2,055 ✭✭✭probe


    bonkey wrote: »
    I would equally suspect that no-one who lives at 10m+ had problems, nor even those at 5m+.

    If you look on google earth, the river Shannon around Castleconnell is about +20m above sea level. Add another 10m above river level and you should be safe. You might be comfortable with 5m. I won't argue.
    The reason I was surprised is that you didn't bother pointing out that your advice wasn't based on the frequent, or even infrequent flooding events that will happen in the lifetime of someone living in any given location, but rather on a possible "doomsday" scenario that may or may nor occur sometime in the next epoch...and even then it seems that your 30m is based on an "I have no idea of what the effects might be" guess.
    Most of the Mediterranean has an earthquake risk. France didn't impose regulations to earthquake proofing buildings until 1992. Call me a "doomsday scenarioist" if you wish, but I won't live or work in a building that isn't "parasismique" - ie quake resistant.

    As far as "I have no idea of what the effects might be" is concerned, logic tells me that there is a large force of energy in the river as it exits into the ocean. If a tsunami hits it with equal or greater force coming from the opposite direction, the water will "hit the ceiling" - how high it goes depends on the energy in the tsunami wave.


  • Registered Users, Registered Users 2 Posts: 15,443 ✭✭✭✭bonkey


    probe wrote: »
    If you look on google earth, the river Shannon around Castleconnell is about +20m above sea level. Add another 10m above river level and you should be safe. You might be comfortable with 5m. I won't argue.

    If you go back and look at what you originally wrote, you'll see now why I was so incredulous.

    You won't quibble with the difference between 5m and 10m above river level....but your original recommendation was 30m above normal river height (and not above sea-level, as you now seem to be saying).

    Most of the Mediterranean has an earthquake risk. France didn't impose regulations to earthquake proofing buildings until 1992. Call me a "doomsday scenarioist" if you wish, but I won't live or work in a building that isn't "parasismique" - ie quake resistant.
    The med is prone to quakes. The Canary Islands are not prone to falling into the ocean with any regularity.

    Rather than taking Mediterranean France....would you argue that buildings in Ireland need to be quake-resistant? There's no fault-lines which are liekly to ever cause a significant quake...but just like the Canaries, you can never be too sure, right?


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  • Registered Users, Registered Users 2 Posts: 807 ✭✭✭Jim Martin


    http://www.clare.fm/news/esb-defends-water-release-during-clare-november-floods

    Surely, had the ESB kept the water level down before the expected floods, they may have been able to control the situation better!


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