Flooding – dam incompetence

Impetus

I was in Cork city this morning around noon. The tide was out, and there was about 1m of unused capacity in the river system – to dump additional flood waters in anticipation of next week’s rain, without a risk of flooding. In times of heavy rainfall, reservoir water should be dumped at maximum safe flow levels (ie to prevent future flooding), making use of all exit points to the sea, to provide buffer space to hold future rainfall during high tides. The powers that be have not learned a lesson from November 2009.

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

I attempted to check river levels at https://waterlevel.ie and found that the nearest river level gauge on the River Lee was in Ballymakera, some 55 km upstream of Cork city. Ballymakera has a few hundred people at most. The greater Cork area has over 300’000. And no real-time river level reporting on the internet in Cork city.

It is a simple matter to put real-time water level gauges at high risk points in low lying areas, available on the internet, whose readings can be used to guide the amount of water released from upstream hydro power stations. The issue of maximising power generation should be thrown out the window in the circumstances. One wind turbine would produce more power than the River Lee could.

The incompetence of the people responsible is alarming.

Carawaystick

How do you know the esb don't have a river level measure on the Lee? I'd imagine there would have been a measure at the power station on the right bank near the Marina.

Impetus

Carawaystick wrote: »

How do you know the esb don't have a river level measure on the Lee? I'd imagine there would have been a measure at the power station on the right bank near the Marina.

The Marina is not the weakest point in the system. The weakest points in the system are along the river near the bridges in the city centre. www.waterlevel.ie have no gauges on the River Lee anywhere in Cork city. I was in town again today, and the tide was low, and the river had again about a meter to spare below bridge critical level.

If these data on levels were collected and fed back to the sluice gate control room at Inniscarra (or more likely Ardnacrusha from where the Iniscarra dams are remotely controlled), the water could be dumped at maximum safe velocity to take advantage of low tide periods, and empty the reservoirs, in anticipation of further rainfall. Incompetence is causing all this flooding and flood risk. Not mother nature!

Markcheese

I passed the upper lee by the gearagh about 3 weeks ago.. and was surprised at how low the water was ... i've no idea if the esb watching long range forecasts though...i'm assuming the esb know exactly how long water released from inniscarra takes to clear the city ... but wether they can increase flow to coincide with low tide ...
I'm pretty sure the lee has been bank full... from lee fields back to inniscarra for the last couple of weeks though ..

Impetus

Markcheese wrote: »

I passed the upper lee by the gearagh about 3 weeks ago.. and was surprised at how low the water was ... i've no idea if the esb watching long range forecasts though...i'm assuming the esb know exactly how long water released from inniscarra takes to clear the city ... but wether they can increase flow to coincide with low tide ...
I'm pretty sure the lee has been bank full... from lee fields back to inniscarra for the last couple of weeks though ..

I have no doubt that the release of water is controllable (electro-mechanically) and remotely. In the 2009 flooding, media reports said it was done remotely from Ardnacrusha. It seems to me that there is a culture/instruction within ESB to maximise the use of the water for generation purposes. Instead of proactively dumping water during periods of risk, making maximum use of low tides. To do so you need to be able to monitor the river height in the city centre at the most critical flood risk points, and slowly increase the sluice gate opening, until you are getting close to safe high water mark at these critical points. If this happens you reduce the flow slightly so it continues to maximise the discharge rate, while at the same time not flooding the place.

The entire process should be automatically monitored in real time. However there is nothing to stop one from doing the job manually - even if it means putting observers watching the river in the city at critical times, who can call the control centre on a mobile phone and give the person in the control room feedback.

I am sure ESB is paying met.ie for accurate rainfall forecasts. They are also available here:

http://www.wunderground.com/cgi-bin/findweather/getForecast?query=Cork%2C+Ireland

You click on customise and check the precipitation accum. total, and hourly liquid precipitation boxes and it shows up as green on the chart on an hour by hour basis.

You can even get detailed forecasts further upstream in the Lee - eg
http://www.wunderground.com/q/locid:EIXX3370;loctype:1

sheesh

I wonder if a level measure is required. as it is tidal surely it is predictable also the 1 meter of capacity you say was there the level at the time would be set by the sea level.
so they could have been draining the reservoir and it would have been the same level as the level of the water would have been set by the level of the sea.

mickdw

Impetus wrote: »

I have no doubt that the release of water is controllable (electro-mechanically) and remotely. In the 2009 flooding, media reports said it was done remotely from Ardnacrusha. It seems to me that there is a culture/instruction within ESB to maximise the use of the water for generation purposes. Instead of proactively dumping water during periods of risk, making maximum use of low tides. To do so you need to be able to monitor the river height in the city centre at the most critical flood risk points, and slowly increase the sluice gate opening, until you are getting close to safe high water mark at these critical points. If this happens you reduce the flow slightly so it continues to maximise the discharge rate, while at the same time not flooding the place.

The entire process should be automatically monitored in real time. However there is nothing to stop one from doing the job manually - even if it means putting observers watching the river in the city at critical times, who can call the control centre on a mobile phone and give the person in the control room feedback.

I am sure ESB is paying met.ie for accurate rainfall forecasts. They are also available here:

http://www.wunderground.com/cgi-bin/findweather/getForecast?query=Cork%2C+Ireland

You click on customise and check the precipitation accum. total, and hourly liquid precipitation boxes and it shows up as green on the chart on an hour by hour basis.

You can even get detailed forecasts further upstream in the Lee - eg
http://www.wunderground.com/q/locid:EIXX3370;loctype:1

I like the thread title!
Are you seriously saying that the esb actually retain full reservoirs even when unprecedented rainfall is expected and they don't take the opportunity to let water off when the rivers are low.
If that is the case, it's shocking and they should be held liable if clear opportunity existed to release water.

TheChizler

sheesh wrote: »

I wonder if a level measure is required. as it is tidal surely it is predictable also the 1 meter of capacity you say was there the level at the time would be set by the sea level.
so they could have been draining the reservoir and it would have been the same level as the level of the water would have been set by the level of the sea.

Good point, the height of the river is mainly a function of the riverbed level, the tide, and what's let through Inniscarra, I doubt the handful of tributaries between the dam and the city make much of a difference.

Also the ESB more than likely have their own private level measures which aren't on that website.

Edit: I stand corrected, tributaries make up 30% of the catchment area downstream.

http://www.lee.cfram.com/reservoirs.html

Impetus

sheesh wrote: »

I wonder if a level measure is required. as it is tidal surely it is predictable also the 1 meter of capacity you say was there the level at the time would be set by the sea level.
so they could have been draining the reservoir and it would have been the same level as the level of the water would have been set by the level of the sea.

It is not just the river Lee flow rate variables. You also have the River Bride, which is draining a different catchment area. Fine the river level as far as tidality is measurable based on tide tables. But it seems to me that there is no excuse for not having accurate real-time gauges at low city centre points to monitor the overall real river height. The River Bride is not restrained by the dams.

Impetus

TheChizler wrote: »

Good point, the height of the river is mainly a function of the riverbed level, the tide, and what's let through Inniscarra, I doubt the handful of tributaries between the dam and the city make much of a difference.

Also the ESB more than likely have their own private level measures which aren't on that website.

Why do we have an expensive open, state paid for https://waterlevel.ie website? Which completely ignores river levels in the second city? Surely incompetent. The ESB may have their own facilities - but this smells like Oirish wasteful duplication

Impetus

mickdw wrote: »

I like the thread title!
Are you seriously saying that the esb actually retain full reservoirs even when unprecedented rainfall is expected and they don't take the opportunity to let water off when the rivers are low.
If that is the case, it's shocking and they should be held liable if clear opportunity existed to release water.

I am saying that the ESB should go overboard to empty the reservoir as fast as possible during high flood risk times such as we have at the moment, making maximum use of low tides. You can't predict future random rainfall precisely (which patch of ground the water will fall on and into which river that might flow). You just have to leave "the bath as empty as possible" so it can retain unexpected and expected precipitation.

TheChizler

Impetus wrote: »

Why do we have an expensive open, state paid for https://waterlevel.ie website? Which completely ignores river levels in the second city? Surely incompetent. The ESB may have their own facilities - but this smells like Oirish wasteful duplication

Who's incompetent in this scenario? Just because levels for the Lee aren't reported on that site doesn't mean the ESB aren't fully informed.

Just on your OP; while the tide is out maybe the dam is letting out water at the max it can without causing flooding in communities closer to it, the level up here could be borderline flooding but look fine in the city when the tide is out.

mickdw

Impetus wrote: »

I am saying that the ESB should go overboard to empty the reservoir as fast as possible during high flood risk times such as we have at the moment, making maximum use of low tides. You can't predict future random rainfall precisely (which patch of ground the water will fall on and into which river that might flow). You just have to leave "the bath as empty as possible" so it can retain unexpected and expected precipitation.

Yes I understand you. Do they not do this though. It's downright irresponsible if they don't.

Stinicker

Ardancrusha should be demolished and let the Shannon drain again instead of flooding half the country. The economic benefits or getting rid of Ardnacrusha far outweigh the minuscule amount of Electricity it generates now.

Markcheese

Impetus wrote:

It is not just the river Lee flow rate variables. You also have the River Bride, which is draining a different catchment area. Fine the river level as far as tidality is measurable based on tide tables. But it seems to me that there is no excuse for not having accurate real-time gauges at low city centre points to monitor the overall real river height. The River Bride is not restrained by the dams.

The bride valley is a totally different shape to the lee valley . Its mainly wide and flat (from crookstown to the lee anyway, so its flooding and the effect is very different ...

fits

Stinicker wrote: »

Ardancrusha should be demolished and let the Shannon drain again instead of flooding half the country. The economic benefits or getting rid of Ardnacrusha far outweigh the minuscule amount of Electricity it generates now.

It generates 2% of our total powee requirements. Thats not miniscule at all.

Markcheese

Stinicker wrote:

Ardancrusha should be demolished and let the Shannon drain again instead of flooding half the country. The economic benefits or getting rid of Ardnacrusha far outweigh the minuscule amount of Electricity it generates now.

I cant say that I know much about the shannon system - but wouldnt there be a very high risk of increased flooding below ardnacrusha if you got rid of it .

Capt'n Midnight

Tide predictions for Cork
http://www.ukho.gov.uk/EASYTIDE/EasyTide/ShowPrediction.aspx?PortID=0753&PredictionLength=2

Difference high and low tide is six hours.
There is the slight problem that water takes time to flow down stream.
How fast does the river flow ?
If it was 10Km/hr then releasing water 55Km upstream would mean you'd have to do it at high tide to hope the pulse reached there at low tide. And if the speed changes as it would do if there was more water might change the arrival time.

IIRC on the Shannon it takes days for the water to flow down.

Impetus

UCC has a river water height monitoring station at The Maltings*. This is on the net at:

http://77.74.50.157/cfw/

"It is our ambition to expand the system and implement a relatively dense network of up to 15 monitoring stations in the Lee and sub catchments around Cork. This roll-out of new monitoring stations will rely on sponsorship of new stations. However, with commitments of support from hardware suppliers, and ongoing support from IDS Monitoring and Partners the cost of new stations for this project is significantly reduced. To find out more about sponsorship of a new station or maintaining an existing station please click here. "

"What the numbers mean...

The station at the Lee Maltings is located near the Mercy Hospital. The water level values on this station are based on a local datum. If water Levels at this station exceeds 4.8m it is possible that some locations (e.g Probys Quay) will see start some minor flooding. If the water exceeds 4.9m it is likely that the flood will spread and threaten some buildings. A reading of above 5.0 m at this station is usually associated with more significant flooding at the eastern end of Oliver Plunket Street and may spread to other areas. By way of reference the peak water level associated with major flooding on Feb 4th was 5.285m and on Feb 3rd was 5.237m.

The Station at the Angler's Rest is located downstream of where the river Shournagh joins the Lee. Water Levels here are greatly influenced by discharge rates from Inniscarra Dam. Again, this station uses a local datum. A water level of 2.5m at this station is associated with flows in excess of 150m3/s and normally involves flooding of the Lee fields. High flows at this site influence high water in the downstream tidal zone."

*map: https://www.google.com/maps/@51.8984493,-8.4839934,18z

Impetus

Capt'n Midnight wrote: »

Tide predictions for Cork
http://www.ukho.gov.uk/EASYTIDE/EasyTide/ShowPrediction.aspx?PortID=0753&PredictionLength=2

Difference high and low tide is six hours.
There is the slight problem that water takes time to flow down stream.
How fast does the river flow ?
If it was 10Km/hr then releasing water 55Km upstream would mean you'd have to do it at high tide to hope the pulse reached there at low tide. And if the speed changes as it would do if there was more water might change the arrival time.

IIRC on the Shannon it takes days for the water to flow down.

You are only talking about a short distance between the hydro dams and the city centre here. Under 10km. With a few monitoring stations passing data back in real time to the control system for the sluices, it is similar to the issue of maintaining a dynamic green wave of traffic lights along a boulevard, to keep heavy traffic flowing to maximize the carrying capacity of the urban road system. (Yet another issue beyond the capability of Irish local authorities).

There are two main issues:

1) Dredging and clearing away objects that block the river flow into the sea and
2) Using real-time data on river levels collected at critical points along its path, to control the movement of the sluice gates on the dams.

When I was young, I often saw several dredging boats working along the River Lee to clear the river basin of mud. I have never seen a single dredger of late.

If you missed the radio interview on RTE Drivetime with the lady in Clare who was involved with getting a low loader (truck) to evacuate her mother who was wheelchair bound from a house which was under flood attack, you might want to listen to it. The non-wheelchair bound members of the household used a boat to escape:

http://www.rte.ie/radio1/drivetime/programmes/2015/1214/753512-drivetime-monday-14-december-2015/?clipid=2054873#2054873

Click on the item on Clonlara, CE

Impetus

Markcheese wrote: »

I cant say that I know much about the shannon system - but wouldnt there be a very high risk of increased flooding below ardnacrusha if you got rid of it .

Please listen to the interview at the bottom of http://www.boards.ie/vbulletin/showpost.php?p=98118748&postcount=20 if you haven't already heard it on RTE R1.

Markcheese

Port of cork regularly dredge down river of the bridges ... methil marra remove shopping trolleys ect and other junk from both channels reasonably frequently ... dunno if theres much point in dredging the river in the city itself ...

Impetus

fits wrote: »

It generates 2% of our total powee requirements. Thats not miniscule at all.

It seems to me to generate 27 MW, which is about 0.45% of the total demand - based on 6 GW.

https://www.esb.ie/main/about-esb/power-stations-pdfs/ESB_LEE_HYDRO_STATIONS.pdf?v=20140801

It is a matter of priority - do you want the city to be flooded for your 27 MW (or part thereof - because when it is wet, this baby is running at close to capacity anyway). Fine ESB (by whatever brand name may have some insurance - but electricity consumers have to pay the premium in higher electricity charges).

It is a matter of priority. An issue which appears to beyond the comprehensive of overpaid ESB group idiots. And gov.ie regulators. And the court system of Ireland.

The soaking wet banana republic, run by ejits.

If anything this dam could generate far more electricity, if it was fitted with more in number and more in energy efficient turbo generators. Discharging far more water at the same time (which discharge should be driven/controlled to take maximum advantage of tidal levels).

Impetus

A picture of the River Lee today, taken at 12h35, showing the spare capacity of the river (at a guess close to 80cm with spare for comfort) to carry more water at the time in question. A capacity wasted. Meanwhile above the dam, the water levels are high. The low tide today was at 15h44.* (leaving several hours to dump water, without any risk of flooding).

The dam is the main solution available to store excess short-term rainfall to prevent urban flooding.

This flood prevention resource is being wasted by incompetent people, who operate by remote control from nearly 100km away from the point of reality and they seem to have zero knowledge of the real-time water level, at critical points in the system.

https://s3-eu-west-1.amazonaws.com/riverimage2000/20151217_123558%5B1%5D.jpg

*https://www.sailing.ie/Portals/0/Cobh%2012-2015.pdf?ver=2014-06-13-000000-000

L

Impetus wrote: »

It seems to me to generate 27 MW, which is about 0.45% of the total demand - based on 6 GW.

From memory, Ardnacrusha is about 90MW. It's ~4 of those units.

Impetus

L wrote: »

From memory, Ardnacrusha is about 90MW. It's ~4 of those units.

So? My number referred to Carrigadrohid on the River Lee - please see the ESB info on this site which I attached before adding your gems to this thread :-)

(Carrigadrohid on Lee appears to be remotely controlled (sluice gates etc) by Ardnacrusha on Shannon staff, who appear to be operating in the blind.

Presumably the minuscule amount of power generated by this plant does not warrant the staff cost?

L

Impetus wrote: »

So? My number referred to Carrigadrohid on the River Lee - please see the ESB info on this site which I attached before adding your gems to this thread :-)

You were replying to fits who was talking about Ardnacrusha.

Macha

Impetus wrote: »

So? My number referred to Carrigadrohid on the River Lee - please see the ESB info on this site which I attached before adding your gems to this thread :-)

[mod] *sigh* can't we just all be a little more polite (and a little less passive-aggressive) to each other? Tis the season, etc..[/mod]

TheChizler

Impetus wrote: »

A picture of the River Lee today, taken at 12h35, showing the spare capacity of the river (at a guess close to 80cm with spare for comfort) to carry more water at the time in question. A capacity wasted. Meanwhile above the dam, the water levels are high. The low tide today was at 15h44.* (leaving several hours to dump water, without any risk of flooding).

The dam is the main solution available to store excess short-term rainfall to prevent urban flooding.

This flood prevention resource is being wasted by incompetent people, who operate by remote control from nearly 100km away from the point of reality and they seem to have zero knowledge of the real-time water level, at critical points in the system.

https://s3-eu-west-1.amazonaws.com/riverimage2000/20151217_123558%5B1%5D.jpg

*https://www.sailing.ie/Portals/0/Cobh%2012-2015.pdf?ver=2014-06-13-000000-000

That's not that low, and looks like it's flowing fairly fast. What was the water level like upstream of this in the narrower sections? Water level in the city is largely dictated by the tide, not the discharge from Inniscarra.

Markcheese

I was in the city around 6 last night and the water in the north channel was fairly low - but really flowing fast, if the river in the city had been full to the bridges , ( from released river water ) then up stream would have been badly flooded...

Impetus

TheChizler wrote: »

That's not that low, and looks like it's flowing fairly fast. What was the water level like upstream of this in the narrower sections? Water level in the city is largely dictated by the tide, not the discharge from Inniscarra.

There are two causes of flood risk in Cork. Extremely high tides + wind coming from the wrong direction is one. Another is river/dam mismanagement. In 2009 we had an overflowing reservoir caused by heavy rain, which was forecast about a week in advance, and this was allowed to accumulate in the reservoir with massive consequences for many parts of the city. We are playing with fire by not managing the discharges of this reservoir during periods of prolonged / heavy rainfall. Cork airport weather station reported over 100 mm of rain over the past 7 days to 15.12.2015, in the dozy met.ie site that is a day out of date. Heavy rainfall forecast = keep the reservoir as empty as possible time, and make use of periods when the tide is out to maximise dumping of water - managed up to an engineered water height for the river in the centre of the city.

The entire process (regarding dam management) could be automated, by creating a computer model which takes into account forecast rainfall, water height inside the reservoir, tide table data, and river height at critical city centre locations. The same model could also monitor tidal risks by looking at tide table data and wind speed/direction forecasts.