Solving South Galway Flooding – Good start but complexity slowing feasibility study

There has been a lot going on over the past 6 months with substantial level of data gathering from extensive home/farm flooding surveys, public consultation, LIDAR and satellite data collection.  This information is crucial in developing an accurate and complex hydrology model of South Galway that will allow

  1. A more accurate prediction of flooding dynamic  that will feed the Cost-benefit analysis
  2. The impact of proposed solutions (attenuation, bunding, channels)

There is a lot of data required to develop an accurate model and the models itself is very complex to develop. This we are told is leading to a delay in the final feasibility study being pushed out from Jan 2019 to May 2019, and could mean a delay in overall project by the same timeframe.

Other concerns are that the NPWS has put more or less a moratorium on Swallow holes reinstatement/maintenance (anticipated light maintenance – removal of wraps and tress won’t be a major issue).

Abbreviations :

  • RH: Ryan Hanley, Engineering Design Consultants
  • MMD : Mott McDonald,, Environmental consultants
  • GCC : Galway County Council
  • OPW: Office of Public Works
  • SGFRC : South Galway Flood Relief Committee

Information Compilation

A lot of the feasibility study stage is about compiling a lot of information relevant to flooding to assess flood extents and feed cost-benefit analysis which will determine the justification and budget for flooding solutions.

Land Surveys

RH have (almost) completed the most extensive survey of land, homes, farms in South Galway  to date in relation to flood levels.   The survey team collected finished floor levels, path levels, historic flood levels, flooded road levels, bridge and structures data including :

  • 174 houses, Farm buildings, septic tanks, fuel storage
  • 24 additional farm buildings
  • 10 commercial properties,
  • 47 bridges and culverts and several kilometres of roads.

This information is currently being compiled by RH into a GSI database to be used in the cost-benefit analysis.

Note : There are several areas that have not been completed yet, as they are waiting on additional LIDAR result before surveys are commissioned – if you are concerned, please contact Galway County Council.


LIDAR gives an extremely accurate land topography (heights of land to a few CM) .  There was some historical LIDAR Data around South Galway but several key pieces were missing.  This year additional LIDAR flights were commissioned to fill in some missing pieces (Around Caherglassaun-Cahermore, Caherawooneen, Turloughmore/Tulla, Kilmacduagh, Gortnaculla, Liseen, Tarmon).  There is still more to be commissioned around Kilchreest, Ardrahan, Killinney, Lough Cutra and the M18 towards Tubber

Salinity Monitoring

MMD is looking to get salinity monitoring (Kinvara Bay)  data from EPA and NUIG and this will be added to the Hydrology model

Public consultation Day

Public Consultation Day took place on 3 May 2018 in O’Sullivan’s Hotel, Gort, and was attended by representatives from GCC, OPW, RH & MMD. 55 people signed the attendance sheet but many more attended.  The themes :

  • Concerns that the scheme would affect salinity in Kinvara Bay
  • Assurances that the proposed scheme would include measures to reduce rapid run-off the Slieve Aughty Mountains

Hydrology Modelling

The hydraulic Modelling has been significantly complex and initial (3d) models were too slow for running the number of scenarios that needed to be run for forecasting, solution iteration etc. These models were replaced by simpler models (1d) that would fit initial feasibility study assessment.  The more accurate models that will still be used for signoff but there is more work in creating these models leading to delays.

hydrology model

Turlough Levels Monitoring

There has been a significant increase in the number of Turlough Monitors in South Galway and many people will have seen GSI people installing monitors (mainly temporary) .  The following GSI monitors were installed in Autumn 2016:

  • Caranvoodaun
  • Caherglassaun
  • Coole
  • Blackrock
  • Garryland
  • Newtown
  • Hawkhill
  • Managh
  • Termon North & South
  • Ballinduff
  • Roo
  • Coy
  • Cahermore
  • Labane
  • Kiltartan
  • Tulla

These monitors were installed in Summer 2017.

  • Cockstown
  • Ballyboy
  • Ballylee Sinks (north and south)
  • Castletown sink

There are also several permanent monitors being installed. Here is a shapshot image of the monitors.

South Galway Turlough Monitors – Courtsey of Geological Survey Ireland (2018)

Turlough Levels (Satellite)

As several of the monitors are new, GSI/TCD are also using new techniques to analysing satellite imagery to determine real-time Turlough levels over the past 3 years.  This imagery is produced by the ESA Sentinel-1 satellites using SAR (synthetic aperture radar) and works through cloud or at nighttime  and is particularly good at highlighting waterbodies. It has captured hi-resolution imagery of Ireland every 2-3 days since 2015 and therefore has captured flooding events/water levels so it can be used to determine Turlough/flooding levels where there was no monitors – (The good news is that this applies to all of Ireland, and not just South Galway).

SAR Imagery of South Galway – Christmas Day 2015 :   Geological Survey Ireland (2018), ©Copernicus data (2018)

Weather Prediction/Climate change models

There is significant work on developing more realistic Weather prediction/climate change models for the 1:100 year, 1:1000 year rainfall.   TCD/GSI are working on updating their models to have more accurate weather forecasting. This are collaborating with the Irish Centre for High-End computing to do weather, climate and rainfall prediction  to provide long term ‘synthetic rainfall simulations‘ that will be used by the hydrological model to provide the 1:100 flood limit estimations.

Uplands Attenuation

From being highlighted as Public Consultation day and also from the SGFRC There has been some additional work on looking at potential uplands attenuation.  What happens if you slow-the-flow and flatten the peaks?  Some attenuation scenarios show limited impact on upland and lowland Turlough while other attenuation scenarios show possible lowering of low-land Turloughs by 1.5m and consequently lowering upland Turloughs by 0.5m. This is the kind of early analysis being done with the model currently.


In order to progress the solution RH have drawn in conceptual channels (link – 20m each side, depth unfixed) between the different areas and are working with MMD to do an initial Environmental Investigation – looking at habitats, impacts etc of proposed work.

Initial Environmental Assessment

Initial findings highlight some bat populations, woodlands and limestone shelfs as part of Coole Park and Caherglassaun.  While it might be ok to take away some woodland within the channel., digging into limestone shelves may be more problematic.  The salinity of Galway Bay will also need to be addressed.  The channel definition have allowed the advancement of seasonal ecological surveys so the 2018 season isn’t lost.

Advanced Works

The SFGRC highlighted several areas could be problematic for the South Galway Communities that would need to be resolved in the short term.  GCC outlined in the project brief the possibility of doing some Advanced works and RH created an overall list of some areas for potential advanced works.


Advanced Works Description Status
Reinstatement of Swallow Holes There was potential to re-instate some significant swallow holes that have become filled in over the years. This has hit a proverbial black hole – NPWS have indicated that Swallow hole clearance is not likely to form part of the scheme, as the effects of clearance are difficult to predict and it would be extremely difficult to demonstrate that work around swallow holes would not have a significant effect on Natura 2000 Sites.  It was accepted that clearance of large artificial deposits (bale rap, and timber debris etc.) could potentially be removed.

SGFRC highlighted that this could be seen as maintenance of an SAC which doesn’t require appropriate assessment.

Overall – SGFRC are not happy with this position.

Culverts between Caherglassaun and Cahermore (Leeches) SGFRC highlighted concerns of the GCC-made dam between Caherglassaun and Cahermore. The concerns here is that the new height of the road with a few 12 inch pipes  will hold back water into Caherglassaun/Coole/Tierneevin, Gort, Crannagh, Kiltartan, Corker etc.  And add flood risk to these communities before flood scheme gets under way. Stalemate here –  GCC raised the road without any proper analysis (threw a few 12inch pipes down) but raised the road 6ft so as long as this remains – they may be responsible for uplands flooding.   If GCC install bigger culverts, again without proper analysis, then again they could be responsible for downstream flooding.


With the lack of detailed flow analysis – it is difficult to ascertain what to do here as an interim measure.  Work will probably not proceed.


Cahermore to Kinvara Overland Flowpath Reinstatement Measures SGFRC highlighted concerns that the Cahermore pipe outlet is 18 inches below the surrounding land and that it needs be fixed.  They also highlighted that the link between Cahermore and the pipe could benefit from a culvert Will form part of the permanent solution rather than Advance Works
Rinrush Access SGFRC/RH discussed several options a Rinrush Emergency Access Road to help avoid the complete isolation of the community there for 6+ weeks during flooding Early stages but this looks promising for the Rinrush community but with details to be worked out (Needs environment assessment, landowner agreements) etc.
Roxborough Demesne: This is the 1st house that floods – flash flood for several hours backs into Paddy McGlynn’s place. Early stages but looks favourable for advanced works – probably done in phases. Volume of water being dealt with won’t have any impact on Grannagh/Blackrock. (Needs environment assessment etc)



Unfortunately, with its complexity and refactoring, it is looking like the hydrology modelling completion aspect will delay feasibility study by 5 months. (the initial model was supposed to be delivered in Jan)  – there seems to be a correlation of several factors:

  • Model has been previously used in Academia and not as a core technology for analysis and simulations – it was too slow to produce results.
  • The updates to the model are quite complex and difficult to converge
  • More aspects to the model – salinity and uplands rapid-run-off analysis

GSI have indicated that they don’t foresee any more delays in the model and that it’s now in good shape – it will be continuously refined as more data comes in.


The success of this project relies heavily on science as this is an incredible complex and sensitive project.  One the positive sides- Galway County Council, the consultants and GSI are so far extremely thorough.

  • Full land Surveys – to understand homes being threatened
  • Turlough monitors/Satellite SAR analysis
  • LIDAR data for accurate hydrology modelling
  • Full hydrology modelling of the Turlough network
  • Latest Weather prediction techniques.

Also the consultants have been creative in working out ways to continue to progress -developing channel concepts to allow environmental feasibility to progress.  The steering committee seem to be adaptive and supportive where change is needed.   There is additional work being undertaken which will have a positive impacts on the accuracy of results.

While this complexity and widening scope of work is pushing the feasibility study out by 4-5 months – It is not clear on the impacts on the overall project and if this 5 months will be added to the complete project or if something can be done to bring the timeline in? – This is question we will ask GCC.

Another concern is the NPWS position on ‘untouchable’  Swallow-holes, limestone shelves, etc  that may end up blocking some aspects of a solution. We all want to avoid a situation where a solution is not possible because of an environmental snag even if we can prove overall that this is a significant environmental benefit to this scheme.  This has become one of the big risks for this project and I will be addressing the Swallow-hole situation in an upcoming blog

Overall, the SGFRC is complementary of the thoroughness of the work being done by Ryan Hanley, Mott MacDonald, GCC, GSI/TCD and is supportive of getting the right level of accuracy to ensure we get a long-lasting flood solution.  We don’t want to have to be revisiting this again in 10 years time – However, we can’t afford more slips that introduce another winter cycle into the flood relief program.

-David Murray,

Chair South Galway Flood Relief Committee









South Galway Floods – Public Consultation Thu 3rd May

Your input and local knowledge is important to ensure the development of an informed publicly acceptable scheme.  It’s time to have your say!
Galway County Council intend to progress a flood relief scheme to alleviate flooding which has impacted the Gort Lowlands area. For more information you can see the leaflet below:


Mott MacDonald has been appointed by Galway County Council to carry out an Environmental Assessment of the proposed South Galway (Gort Lowlands) Flood Relief Scheme.  The purpose of this Public Consultation Day is to seek initial views from the public in relation to the key issues that should be addressed as part of the South Galway (Gort Lowlands) Flood Relief Scheme, and to highlight points of local importance that may constrain the design of potential flood alleviation measures.
Please call into Sullivan’s Hotel, on Thu 3rd May 2018 between 3pm and 9pm and give your feedback on the flooding there,.  You can fill out this questionnaire there, or at home and send it to the communications co-ordinator for the scheme, Ms. Rita Mansfield
By post:
Ms. Rita Mansfield
South Galway (Gort Lowlands) Flood Relief Scheme Communications Coordinator
Mott MacDonald Ireland Ltd., 5 Eastgate Avenue, Little Island, Co. Cork
By e-mail:


Please give your support to the community that has had to endure 5+ severe flooding events since 1990 – It’s threatening our farming community, our schools, our heritage and our national parks (The Killing of Coole)

-David Murray 

The Killing of Coole

Coole Park is a nature reserve and one of the most beautiful areas in Ireland with a rich mix of natural beauty, a vibrant heritage history and a special area of unique environmental importance.  We see however that with extreme weather events – all of these aspects of Coole Park are being very badly threatened. We need to ensure that Coole Park is well protected by the emerging South Galway Flood Relief scheme.

The Walled Garden

In 1768 Robert Gregory,  Chairman of the East India Company, bought 600 acres from Oliver Martyn of Tulira and this became the foundation of Coole Park as we know it today.  In 1770 he built Coole house and also started the construction of a Walled Garden in 1775.  In 1776, it is reported in ‘A Tour of Ireland’ that many miles of walls are being constructed and also that “Mr Gregory has a very noble nursery, from which he is making plantations, which will soon be of great ornament to the country”.   As part of the Walled Garden, beech trees and a line of Yew trees are planted. Richard Gregory continued the work and also had a bust of Maecenas transported from Italy.

Coole Park is famous for its Autograph Tree and Lady Gregory (Wife of Robert Gregory’s great grandson) also had a fondness for the Yew and in ‘Gods and Fighting Man’,  called it ‘the most beautiful of the wood’.  There are very frequent reference to the line of Yew trees in visitor reports to Coole House.

“That afternoon I found the garden….. I went slowly along, crushing rosemary between my fingers, and wondering at the dark groups of stately Irish yews.”  Signe Toksvig, 1921

Even in the Ordinance Survey 1838 maps we see an outline of the walled garden with the paths, pumps and the  line of ‘evergreen’ trees where the current Yews stand.

And until recently this is what the Walled Garden looked with the line of yew trees in the centre and the Autograph tree on the left.

Aerial View of the Walled Garden at Coole. (Courtesy of Leann Harmon)
The Yews – Pre-2015

These yew trees (Taxus baccata) have become a distinct feature of Coole Park and can reach 400 to 600 years of age and beyond.

 Nature Reserve,  Special Protected area and Special Area of Conservation

In 1983, Coole Park, GarryLand was designated a Nature Reserve which “includes woodland and lake ecosystems which are of scientific interest and that the said ecosystems are likely to benefit if measures are taken for their protection”



It is also a Special Protection Area (SPA) under the E.U. Birds Directive, of special conservation interest for Whooper Swan.  Lastly, it is a Special Area of Conservation (SAC)  with special focus on:

  • Natural eutrophic lakes with Magnopotamion or Hydrocharition – type vegetation
  • Turloughs
  • Rivers with muddy banks with Chenopodion rubri p.p. and Bidention
  • Juniperus communis formations on heaths or calcareous grasslands
  • Semi-natural dry grasslands and scrubland facies on calcareous substrates (Festuco-Brometalia) (* important orchid sites)
  • Limestone pavements
  • Taxus baccata woods of the British Isles  (The Yew)

Coole-Park/Garryland is therefore one of the most specially protected areas in Ireland with significant ecological benefit. It is operated by the Irish National Parks & Wildlife Service (NPWS) who are part of the Department of Arts, Heritage and the Gaeltacht,  currently under Minister Josepha Madigan T.D.  It is their responsibility to ensure that Coole Park (and other Turlough areas) are protected.


Coole Park is now under significant threat from several flooding events and we need to ensure that those that are responsible for its protection are made aware of their responsibilities and do their jobs.

Severe Flooding

Several times in the past 30 years Coole Park has experienced severe flooding – in fact some of the worst flooding in several hundred years. While local people experienced the worst flooding seen in the area in their lifetime – Coole park was subject to an even starker picture –  that of experiencing the worst flooding in centuries –  many of the famous Yew trees that have been around for and estimated 220 years were destroyed by the flooding in Winter 2016 and water was very close to the autograph tree.

The Walled Garden in Flood (28th Dec 2015)  – Courtesy of Sean Brady Aerial Photography

In the past 30 years, we have had a large set of hydrology changes in the South Galway / Kinvara Catchment.  The Slieve Aughty mountains now have significant developments around forestry and windfarms (with their corresponding roads and drains).  Uplands farming improvements have resulted in land being drained more than in times past.    In the Slieve Aughty lowlands there have been rivers streamlined, new culverts installed and inadvertently, some swallow-holes damaged and overflow channels obstructed through land reclamation.

Whatever the reason for hydrology changes the consequence is that Coole Park has become the defacto dumping ground and holding site for enormous amounts of contaminated flood water in South Galway.  This flood water includes pollutants and contaminents from septic tanks, farmyard slurry tanks and farmyard pollutants as well as farmland run-off and significant amounts of silting.  This not only has severe consequences for the environment and human health but it also drastically affects the overall community as the water levels threaten homes, businesses, churches and severely restricts access around several communities in South Galway.

Flooding Impacts

As Coole lake has unfortunately become the dumping ground for run-off water from the Slieve Aughty mountains – there are many significant consequences.

  • Flooding water damage to trees
  • Pollution
  • Wildlife impacts
  • Silting
  • Damage to park amenities
  • Flooding of outlying areas
  • Tourism and Heritage
  • Human Health
  • Farmyard flooding

Flooding water damage to trees

In 1995, 2009 and 2014 and 2015, the famous Walled Garden in Coole Park was inundated with flooding – 2015 being the highest levels.  It covered the picnic benches, flooded the shelters and saturated may of the yew trees and shrubs.  4 of the main yew trees did not fully recover and have since died

Nice weather for retrievers


These Yew trees had survived over 220 years and it shows that the levels of recent flooding allowed in Coole Park are record levels.   Also, it wasn’t just these Yew trees.   A large Yew tree at the Walled Garden car park was damaged, and an copse of Yew trees in Garryland was also severely damaged as well as several Yew tree near Newtown.  Coole Park is a Special Area of conservation (SAC) and Yew Tree (Taxus Baccus) woodlands are called out specifically in this.  We are therefore failing in adequate protection of this SAC.

Another impact on woodland is that flooding causes leaves the forest more vulnerable to storms.  In 2014, there was significant damage to the forest into which Coole Lake had flooded. The waterlogged ground made trees more susceptible to falling in windy conditions.  This is what happened the Yew tree a the Walled Garden Car Park  in Winter 2015

Water levels rose close to the base of the famous Autograph tree which would have made it more vulnerable to falling


Coole lake received waters from many other flooded areas and subsequently caused flooding in areas closer to Coole (Kiltartan, Raheen, Glenbrack, Tierneevin,  etc) .  This involved a lot of farmyard flooding: (Photos : Courtesy of Sean Brady, Aerial Photography)

In this picture it is very clear to see the farmyard slurry contaminating the water system
It is not just the farmyard slurry but many other pollutants that get into the system
Farmyard in Tierneevin
A farm shed in Glenbrack completely immersed in flood water – Water levels should not be allowed to rise to these levels!

A very familiar site all around Coole Lake –  black plastic silage bags caught high-up in the trees. (Newtown Turlough- Coole-Garryland SAC

Several farm yards  around the area are 13m above sea level. In 2015,  Coole Lake rose to 14.78m,  and it overflowed into many farmyards, homes and businesses.  Common farmyard pollutants can include chemical fertiliser, engine oil, grease, fuel, silage wrap, weed killer, pesticides, veterinary medicine etc.  Also at this stage the contents of over 40 septic tanks were being washed into Coole lake.

We see here the plastic bottles being washed up close the hut (Courtesy of Burren Photography)

In many places, there were black plastic silage wrap spread through trees and shrubs all over the park.   With extremely high-level allowed in Coole, this pollution will also be  spread into the lower-lying turloughs and SACs.


Wildlife impacts

Pollution has a devastating on many animals and habitats. In a report from the UK on flooding it states –  “Most natural sites are able to take occasional flooding, but any water polluted by overflowing drains, septic tanks or pesticides from farms and parks is likely to have exacted a toll on many animals.” In addition to these devastating effects of pollution, during the floods of Winter 2015 some habitats were completely flooded and hibernating animals sought refuge from flood waters

Many hibernating mammels were displaced and killed by the several flooding

Another key impact on an SAC is the Kiltartan Cave SAC (Probably the smallest SAC in Ireland!)


This is an 800m long cave and is a habitat for a colony of bats and the SAC is to protect this habitat.  This is the key reason the now famous ‘bat-bridge’ was built (at substantial cost) across the M18 Motorway.  According to Tony Collins, project engineer for the M18 motorway,   it allows lesser horseshoe bats to safely cross the motorway to feeding grounds at Coole Park from their roosting site at Kiltartan Cave which were separated by the motorway. [6]

With extreme levels of flooding in Coole, this habitat is lost and the bat population displaced – something which grates against the EU habitats directive.


As the water leves of Coole Lake rose, the rivers feeding it lost pressure and this resulted in significant amount of silt deposits. This has a big impact on the natural ecosystem, marine life as well as impacting hydrology of the system.


After Winter flooding 2009, there were huge silt banks on the Kiltartan River at Polldeelin
The river after the rise into Coole Lake is very silted

Damage to park amenities

TThe main damage to Coole Park amenities was around the walled Garden and picnic area.  Also the little hut beside the river had its roof lifed too and damaged. The Coole Park Interpretative centre was became flooded. In 2015, there was as estimated  €20,000 of damage done around Coole Park amenities – There is also a potential knock-on impact to  tourism.

Coole Lake environment and upstream flooding

Coole Lake provides a significant amount of attenuation for South Galway, however when it is allowed to reach the levels it did in 2015 is has a huge impact across multiple communities.


Local Flooding from Coole

On a normal Summer, Kiltartan Church is 2 KM away from Coole Park and the lake levels can be just 5m above sea level (AOD) .   The door step at Kiltartan Church is 14.52m Above sea level (AOD) .

In Winter 2015, Coole Lake rose to 14.78m therefore Coole lake essentially backed into Kiltartan Church to a height of 26cm.  (OPW Levels)


In Winter 2015, the level of Coole lake was 18 inches into Kiltartan Church.

Similarly Tierneevin is 2km from Coole lake in the summer and Coole lake backed up into this area as well.  this flooding homes, septic tanks, farmyards, this is what happens if the maximum level of Coole Lake is not maintained.

Coole Lake also flooded homes and businesses in Raheen, Crannagh, Glenbrack and Tierneevin.

According to McCormick/Naughton (GSI/Trinity) ,  the levels of water in the groundwater system can influenced flow rates in a Karst system. and highlights examples where the backwater effect of flooding at the downstream sink reduces the hydraulic gradient and increases upstream river levels. [1] High Coole lake levels mean a drop in pressure upstream causing more water to gather. Swallow holes almost completely stop working in Kiltartan, Roo and Tierneevin  as Coole Lake level back into them and some of the other flows are impacted – even as far back as Ballylee and Blackrock.


As Coole lake flooded it blocked many roads all around its periphery.  The following list details  the amount of time roads were closed in the area around Coole, Garryland, Ballynastaigue

Kiltartan/Corker 91
Crannagh 81
Coole/ Glenbrack
Roo 119

It also flooded the M18 motorway construction for several weeks.

Health Impacts

There is a significant threat to human health from this flooding scenario.   The mental stress and anguish of having your home or livelihood threatened is enormous.  Also many people were affected the severe isolation – not being able to leave your home conveniently.  The threat to physical health by contaminated water and health schemes is significant and private wells can continue to be contaminated long after flood water recedes.

Impacts on Farming

As Coole Lake rose, it covered a large amount of farmland and stayed on the land . Many farms in the area had to be reseeded at a significant cost to the farmer.  As with wildlife, another significant threat is that to farm animals and threat to their health from contaminated flood water.

Tourism and Heritage Impacts

Coole Park is a very attractive destination in the west of Ireland.  Trip Advisor shows it as the #1 attraction with 4.5/5 star reviews.


An article in the New York times explores this area  and indicated that “The grounds are now a national park and preserve of manicured gardens and paths beneath majestic yews.”

The Irish Examiner highlights that “Continuing eastward around the park’s periphery, we entered the Walled Garden through a bright red gate. The scene within was one of classic beauty, manicured lawns, gazebos, picnic tables, a line of yews and the Autography Tree, a copper beech inscribed with the names of the Irish and Anglo-Irish literary greats of the last century.”

Allowing Coole Park to flood increases the risk of damage to the park, the infrastructure, the trees and the wildlife and therefore also to the Tourist potential of the area.

Putting it all in perspective

The following infographic gives a summary of the situation.  Info is compiled from OPW recorded levels and GPS aided levels.


Here are a number of facts.

  • Coole Lake minimum levels are around the 3M (Above Sea level /AOD)
  • Coole Lake maximum level recorded level in 2015 was 14.78 (OPW)
  • Coole Lake can rise to levels of 11m without any major flood threat, which is still an 8m (26ft)  difference from low summer levels.
  • Once Coole Lake level rises above 12m, road access is impacted and farmyards are threatened.
  • Once Coole Lake level rises above 13m, septic tanks and farmyards start to flood and homes are threatened.
  • Once Coole Lake level above 14m, the underground systems (Kiltartan, Tierneevin and Roo) are no longer working and homes start to flood.
  • Once Coole Lake reach 14.5m, several homes are flooding, up to 15 septic tanks are under water and many homes are now threatened


Solving the flooding in Coole Park is a not a choice – it’s mandatory Coole Park is one of the most protected areas in Ireland and allowing severe flooding is devastating to the nature reserve,  several communities and in fact against EU law.   The organisation accountable for Coole Park nature reserve and owns the responsibility for ensuring this is adequately protected against threats (including flooding ) is the National Parks and Wildlife service – NPWS.

We have the best possible chance at getting a right solution here as the South Galway/Gort Lowlands Flood Relief Scheme gets underway.  Galway County council is running the project, we now have design consultants, environmental consultants working toward getting a solution.

The NPWS will also play a key role here according to Dr Enda Mooney, regional Manager, the NPWS is committed to “working  constructively with the design team for the South Galway flood relief scheme and Galway Co. Council to help steer the proposed scheme through the legal requirements under national and European legislation.”

The South Galway Flood Relief Committee has had several meetings over the past 2 years with Dr Mooney to try and demystify the situation that will enable flood relief solutions to progress seamless so that the South Galway Community gets its flood relief solution and that also keep to the letter of EU legislation. We’ve made some great progress on certain aspects and there some very good collaboration here and overall I feel that the NPWS has stepped up the plate.    However, there are still some areas of concern that need to be smoothed out and these will be outlined in the next article which will go into a bit more detail on these issues.

Coole Park was developed by the Gregory’s for hundreds of years and has become a magnificant nature park, with strong cultural and heritage ties.  It was left in the care of the Government in 1927 and taken over by the Forest Service and since 1987 it is  now in the care of the NPWS.  They now have a key reponsibility here to be part of the solution and help and advise the consultants to get a full flood relief solution that will help the South Galway Community and halt the killing of Coole.

In the meantime if you feel strongly about helping to save Coole Park from future serious flooding and in addition to helping the many people affected by flooding in South Galway – please share this  with as many people as you can.  Please comment and leave feedback because it’s our collective voice that can have an impact here.


David Murray, Chair South Galway Flood Relief Committee




South Galway Flooding Survey


As outlined in a 2018 update, the first stage of the South Galway Flood Relief Scheme is a feasibility study and flood risk assessment.   As part of these works the design Consultant Ryan Hanley will be commencing threshold surveys starting during next week of properties in or adjacent to flood zones in the study area.  These surveys are mainly focused on getting information on flood threats and flood extent and not on flooding damage -This nformation can be gathered during later public consultations sessions.

A team from Ryan Hanley will be calling to properties and will have identification and a letter from the OPW.  The key information that will be collected from property owners during the survey will include:

  • the property owner name and address,
  • property use (house, farm slatted shed, commercial premises etc.)
  • Age and construction of the property
  • finished floor level of the property (including basements, split levels etc.),
  • the access level,
  • septic tank location, slatted sheds locations, fuel storage locations, etc.
  • peak flood levels from past events (including 2009, 2015/ 2016, 1995) at or in the vicinity of the property
  • flood impact duration during events
  • brief summary of flood damage (any additional detailed information will be collected at the Public Consultation event).
  • was access to the property cut-off, where did the road / access flood etc., to what depth and for how long, how frequent, what was the length of diversion required if one was possible.
  • External Photograph of the property
  • in some cases, adjacent lands ownership and any knowledge on ground conditions (i.e. is rock near the surface)

This is vital infomation to gather to understand flooding levels and threats and in conjunction with addtional feedback during public consultation (Proposed for sometime in May)

Please support  – Let your neighbours know and please share this if you can.


-David Murray,

Chair, South Galway Flood Relief Committee.

PS:Please don’t underestimate the impact you have by simply liking,commenting on or sharing this.  


Flooding in Ballylee, Rinrush and Newtown

The following post describes the flooding situation around Ballylee, Rinrush and Newtown that happened in the winters of 2009 and 2015. It introduced they catchment and hydrology, the flooding dynamic and impacts on the communities of Ballylee, Rinrush, Deerpark and Newtown.

The Boleyneendorrish river is sourced in north-west of the Slieve Aughty mountains between the peaks of Sonnagh Old and the mountain peak of Cashlandrumlahan (now the site of the Derrybrien windfarm)

Catchment and Hydrology


The Boleyneendorrish is sourced from the northern slopes of Cashlaundrumlahan, through Funshadaun and flows in a mainly westerly direction towards Kinvara but this river goes underground about 11km from Kinvara.  In the background you see the Burren and Kinvara Bay

The rivers starts at an elevation of 350m flows through upland townlands of Funshandaun, Bohaboy, Toormacnevin and Kilbeg.



Looking toward the source of the Boleyneendorrish River flowing through Toormacnevin/Kilbeg. The Derrbyrien Windfram is on the back right of the photo


The river runs through Kilbeg and under several bridges



It then flows into Boleyneendorrish and Gortadragaun and is joined by small streams flowing north from townlands such as Knockoura, Keelderry and Hollymount as well as streams flowing south from Derryvokeel and Scalp. The following is a profile of the flow from Cashlaundrumlahan

The river flows past Drumminacoosaun and under a beautiful stone bridge towards Ballynahowna and again under another bridge at Farnaun and at this stage is the river is 100m above sea level.

It flows swiftly downstream and becomes the Ballycahalan river which now spits into two rivers, a few hundred metres behind (east) of Gillane’s Service Station. One river flows south as the Annagh and Turra river and lows back into Cloon and the other passes on the Gort side or Gillane’s Service Station and over a waterfall into Cloon. This is the waterfall in flood.


These two rivers join another small drain flow from Circular Road, Gort,  to become the Streamstown river which is the river that flows by Thoor Ballylee Castle.

The Boleyneendorrish river becomes the Ballycahalan river and passes under the road close to Gillane’s service station, past Cloonweir and it then becomes the Streamstown river as is passes Ballylee Castle

The river has a weir and outlet that had been used to power a mill in W.B Yeats’ time and it flows past this old millhouse and millers cottage.

Just downstream from Thoor Ballylee lies the ruins of an old mill and millers cottage.

After a few hundred metres downstream from the mill the river turns abruptly west and flows into a swallow hole called Pollanoween (also known and the Hammer Sinks) through crevices between boulders.


Note – as the river veers west, another branch veers east and sinks in a swallow hole called Pollaleen.  Depending on the time of the year, this river can flow in both directions. In a low-water table Pollaleen acts as a sink and water can drain out from Ballylee.  In wet winters, if Lough Coy and Blackrock Turloughs rise significantly, then the sink can become a risk and flow towards Pollanoween.

At Pollanoween, the river goes underground in a north-west direction and re-emerges behind the Church in Kiltartan in a hole called Poulacapple.

The underground section is shown in green and flows close to Newtown hill across the N18 and into Kiltartan at Poulacapple
The underground river (Green) emerging into Poulacapple in Kiltartan

From here, the Kiltartan river runs for about 1 mile and then sinks and re-emerges and flows into Coole Lake,  where it then sinks underground and comes out at Kinvara. Another interesting point is the rise in Kiltartan (Polldeelin) is the meeting point of another underground river coming from the Gort River.

The linkage between Kiltartan and Ballylee can be seen here in a concept drawing. It’s roughly 3km in length and can go as deep as 82m (Well below sea level)


There is roughly a 3-4m level drop between Ballylee and Kiltartan.  According to [1] Artur Kozlowski he dived 1.5 km from Poulacapple toward Pollanoween and he hit a depth of 71 m. Also he dived an unknown hole in Newtown that he named Pollindre [4] which brought him to a depth of 82m.

The swallow at Pollanoween is in fact linked to many different underground channels.  Not only does it come into Kiltartan at Poulacapple, it also links up with the rise of the Coole river. It also has links as far a away as Pollaloughaboo and Pollbeahgy in Carrowkilleen over 11km to the North-West.


Flooding Dynamics

The Ballylee area is very similar to the dynamics described in a previous article Flooding in Grannagh, Blackrock and Skehanna This is where upper catchment drainage flows directly into an underground system and therefore in heavy rainfall these areas are susceptible to rising waters as the underground system is not capable of sinking all of the water.   As with Blackrock, the Ballylee areas have Turloughs (Carrowbaun, Newhall/Newtown and Ballylee Turloughs).  In normal winters, these will rise and store water but in severe winters the water will find an overland course and cause a lot of impacts for the local communities of Rinrush, Deerpark, Cloonanearla, Newtown.

The Streamstown river flows underground but the area around it is landlocked.  In normal wet winters the Turlough areas around Carrowbaun, Newhall, Ballylee rise and join.


This level of flooding can be normal during the a wet winter.  However, if there is excessive rain then the whole area is severely impacted.

Severe Winter Flooding

Once the rainfall goes above a certain level there are several situations that conspire that have a dramatic flooding impact in this area.  The underground systems and Turloughs must handle….

  • Storm surge from the Boleyneendorrish catchment
  • Increased water pressure from Lough Coy and Blackrock Turloughs.  As these Turlough levels rise then the northern swallow hole Pollaleen changes direction and water flows into the Newhall, Ballylee area from the Kilchreest catchment
  • If there is significant rainfall then there can be overground flows from the Kilchreest catchment which can flow through Skehanna and into Carrowbaun, increasing the water flow into the area
  • If Coole Lake or Kiltartan are significantly high then this will impact the level of Kiltartan which will also have an impact on the capacity of underground flows from Ballylee

Rinrush winter flooding

The sum of these effects results is a rapid rise in the Turlough levels and this can result in an overflow through Deerpark/Rinrush area

Rinrush winter flooding2.JPG
From this diagram, the pressures from water coming from Blackrock, Skehanna and Lough Coy along with the Boleyneendorrish surge cause significant flooding in the area and the water eventually flows through Deerpark to meet the Gort River in Castletown

The water overflows through Deerpark and flows across roads and railway track into Castletown where it competes with Gort river to flow underground into Kiltartan.  Here is a snapshot of the overflow through Michael Cahill’s farm in Deerpark.

Again, if we look at this during 2015/2016 flooding levels [3] we see that Ballylee flood levels rises to 19.38m above sea level and Kiltartan rose to 15.01 m (Coole lake level was 14.78m)  which would have put significant pressure on Kiltartan.


What happens eventually is that the Gort River (at Castletown) and overflow from Ballylee eventually fill up Castletown and Ballyloughaun and this is what starts to flow across the N18 at Kiltartan leading to that iconic ‘Niagara Falls type of situation’

Overflow from Ballylee and Gort River at Castletown during the 2008 flooding
Aerial Photograph of N18 Flooding in 2009.  The Ballyloughaun area (Kiltartan Bog) is now saturated with water from Ballylee and Castletown overflows and this starts to cross the N18 (Courtesy Nick Geh)

Interestingly, the flooding in Winter 2015 did not have the same levels because a blocked stone culvert had been replaced with a new one. This is described in the blog Why hasn’t Gort town flooded? 

Basically the new culvert kept the levels of Castletown and Ballyloughaun down (by about 1m) – Here it is in action in Winter 2015 and the levels of Castletown were not as severe as 2009 – but yet still enough to isolate the communities of Rinrush/Deerpark.

New N18 Culvert diverting water from Ballyloughaun/Castletown

Flooding Impacts

There are some very serious impacts to this flooding situation including:

  • Isolated Community
  • Farmyard flooding
  • Farmland flooding
  • Heritage Impacts – Thoor Ballylee
  • Environmental Impacts


Rinrush winter flooding3.JPG

An Isolated Community

One of the worst situations here was that the community around Rinrush, Deerpark and Newtown was completely isolated for a total of 56 days during the Winter 2015 flooding. This meant that 10 families had absolutely no access to the outside world.  The only way that anybody could leave this area was to walk through fields for around 2km. There was a boat that some people used but this was quite risky as it involved crossing moving water and it is simply not acceptable that some of our vulnerable community members have to take these risks.

Over the course of the 56 days, several of these people had critical hospital appointments and had to do this with the risky boat trip.  People here had to try and make it to work every day and some even had to move to alternate accommodation to facilitate this.  The simple task of heading to Gillanes or Gort to get milk, mass or medicines became a significant undertaking.

Not only was this community isolated but it was invisible also.  Very few people could get into them.  There were never any television reports on their plight because they were simply but significantly inaccessible.  Thanks to our recent mobile technology we were only able to get a realistic snapshot when we got to see this through social media.

Homes Flooding

Thankfully there were no homes flooded in Rinrush, however out of 12 homes – 1 was threatened and ended up losing their septic tank also.

Farmyards Flooding

There were two farmyards flooded and as we could see from the previous video this flooding caused great stress and anxiety to people, like Michael Cahill, who had to contend with a river overflowing through his farmyard.


This meant that cattle had to be moved out to the land, fodder as inaccessible and damaged.  This caused significant disruption.  It wasn’t possible to get calf-nuts or other farm supplies as the roads were not passable; it fact it took drops from the Air Corps to get animal feed supplements supplied.  Nobody should have to live with this impact every few years – the previous generation had no memories of flooding but this has happened 3-4 times in the past 30 years.

Farms Flooding

There were over 40 farms flooded, some up to several months. 2 farms had over 50 acres flooded and 10 farms had 25-50 acres flooded. Also, many farms were inaccessible during the flooding period.

Heritage/Tourism Impacts – Thoor Ballylee


I remember 3 years ago visiting TripAdvisor and seeing Thoor Ballylee get 1-Star and it labelled as ‘a national disgrace’ . This was because it had been closed for 6 years due to flooding in 2009.  There was a significant effort by the local community to restore the Castle after flooding and in 2015 there was an official opening of the Castle and it continues to be a major attraction in South Galway.   This was short-lived as the flooding 3 months later filled the castle over 2m of water.


The Impacts of flooding mean that this wonderful place cannot open to the public without requiring continuous investment and community work.

Environmental Impacts

A significant environmental impact is caused with the washing out of farmyard slurry tanks and septic tanks into the water.  Many people in South Galway have water schemes or private wells that are badly threatened by this level of contamination with animal and human waste as well as farm yard chemicals.  South Galway is also peppered with Special Areas of Conservation (SACs) which need to be protected from this level of pollution and solutions need to be put in place.


There are several types of solutions that need to be considered to help combat flooding in this area. For example:

  1. Management of rapid-runoff/Attenuation of the Boleyneendorrish catchment
  2. Emergency Access Route for the community
  3. Swallow Hole Clearing
  4. Keep it flowing!
  5. Farm Building Relocation

Management of Rapid Runoff

The main catchment area for Boleyneendorrish river is 63Km2.  This land now has vast tracts of forestry and there are concerns on the impact of forest drains and roads on the hydrology. It has been proven that deforestation can cause an increase of 15% of rapid run-off and there are also research studies carried out that show negative  long-term impacts of forestry on the hydrology of peatland.   Forestry planning needs to consider impacts to downstream catchment, reduce drainage and provide attenuation solutions in the Catchment.  The South Galway Flood Relief Committee has also shown how a forest road diverted flow from a different catchment into the Boleyneendorrish catchment, adding 10s of acres of additional land to the catchment. Stakeholders such as Coillte have been progressive with proposals for reducing the amount of mound drains and providing areas for attenuation and we will see how this progress in the coming years.

Emergency Access Route for the community.

In addition to better catchment management, there needs to be a provision of an emergency access route for the local community so that they will never be isolated in a severe flooding event.   There could be several options for this and it may involve raised roads and properly sized culverts to cross the flood waters or alternate access proposals.

This is mandatory.

Swallow Hole Clearing

In addition to the previous solutions, the Swallow holes in Ballylee need to be maintained where any blockages can be cleared.

Keep it flowing

When the water was up to the windows in Kiltartan Church in Winter 2015, it was 15.01m above sea level. The level of Coole Lake was at that time was 14.78, only 23 cm below this. This level was already an extra 3-4m of water over the normal summer level of Kiltartan/Polldeelin. This level has to have an impact of the water flow capacity from Ballylee.

If the maximum level of Coole Lake was kept down e.g. by 1-2m, then there would be a larger flow from Ballylee to Kiltartan.   The GSI team that is current working on the flooding analysis of South Galway will be able to calibrate the impact scientifically – it is too complex to guess the additional flow rate of doing something like this.

Farm Building relocation

In addition to the previous solutions, the farmers that have been affected by having their farmyards flooded need to be given proper support for either protection (bunding) or relocation.

In Nov 2017, Joe Healy, president of the IFA said that there must be a national strategy to deal with the significant damage that has occurred on lands and property. This must include relocation as an option in some instances and farmyards must qualify where farmers have had recurring flooding problems.

This needs to be accelerated so that the farming community worst affected in South Galway are given the choice to remove the constant yearly threat to their livelihood.


Rinrush, Deerpark and Newtown are extremely isolated in times of flooding and there is a devastating impact on these communities.  Flooding overflow from Blackrock powers through Skehanna and then through Rinrush washing out farmyards and having impacts on health, heritage, farming and the environment.   Solutions should look at upper catchment management and ensure that if flooding scenarios happen that this community is not cut-off.  Farmers who’s farm buildings are in the overflow path should have strong support for relocation.  The lower-catchment water levels of Coole and Caherglassaun should be managed to give Blackrock and Ballylee areas the best chance to drain off excessive water.

We cannot and should not tolerate vulnerable communities be left with no choice but to live with flooding.  Solutions should be sought from all angles and they should be delivered quickly.

-David Murray


  1. Baptism of Fire : Underwater Exploration beneath the Gort Lowlands: Artur Kozlowski and Jim Warny, 2009, Irish Speleology 18 : 37-42
  2. Groundwater flood risk mapping and management: examples
    from a lowland karst catchment in Ireland, O. Naughton, P.M. Johnston, T. McCormack and L.W. Gill. Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, Dublin, Ireland
  3. OPW Water levels :

What’s happening in 2018 for South Galway Flooding?

I’ve had many people ask the same question over the XMAS break – What’s happening with the floods in South Galway? So I’ve given an outline below on what’s happening.  A quick recap to date  :

  • The design Project Design Brief was released in August and the project put out to tender.
  • 19th Sept 2017 : The results of consultant selection slected ryanhanley as the engineering design consultant
  • 13th-Dec 2017 : The design consultants,  Ryanhanley,  signed the contract to commence project.



What is the flood relief scheme?

The goal of the South Galway -Gort Lowlands project is to deliver a flood relief solution for South Galway – from Slieve Aughty Mountains to the sea.


How will this be delivered?

The project will go through 5 stages as outlined below?

Stage 1 Feasibility Study and Preparation of a local Flood Risk Management Plan and General Scheme Development
Stage 2 Public Exhibition/Consultation
Stage 3 Detailed Design & Confirmation
Stage 4 Construction Stage
Stage 5 Handover of Works and Closeout

Where are we in the process?

As of 13th December 2017, the engineering design consultants (RyanHanley) signed the contract and the project design has officially commenced.  The following diagram shows where we are in the process  and the main stakeholders. (The grey boxes show what has been completed to date)


The project brief indicates contractual timelines from time of project commencement . There are approx:

*Approx duration as there are approval gates between many of these stages


What is this going to cost?

The correct answer is ‘We won’t know until the solutions are assessed’  – We hear figures of €48 million (from last analysis ) and €10 million recently in Connaught Tribune However- If we are to believe the process –  These numbers are pie-in-the-sky until we understand the real cost and frequency of flooding and proposals for solutions to this – until then – there should be no numbers considered.  The focus should remain on getting  the right solution and then we can argue about the cost-benefit! What we don’t want is a provisional financial constraint that starts to immediately impact our solution.

What happens in 2018?

2018 is really all about Stage #1 — Deep dive analysis with some high-level solutions in the form of a flood risk management plan :

  • Draft Hydrology Report
  • Flood Hazard Maps
  • Feasibility report
  • Draft Final Reports
  • Draft Flood Risk Management Plan
  • Steering Group Meeting
  • Communications Plan
  • Website

Here are the key deliverables and their expected timeframes:


So 2018 is really just the starting of the design process – getting all the data in place and some high-level solution options and overall flood risk management plan

At least from the contract signing there is now a fixed timeline in place and we and other stakeholders are very keen to ensure that we monitor progress against these plans

What happens in the meantime if we get flooding?

Galway County Council are currently preparing a ‘South Galway Flood Emergency Response Plan’ – a draft was issued in Nov 2017.  The main goal of the plan is that if South Galway does see itself in the middle of a flooding crisis, our community should expect a co-ordinated and well managed response – rather than the chaos of the past.

Essentially, it takes lessons learned from last flood experience, clarifies emergency criteria and will provide guidelines for flood risk managagement of each key area affected. This will be due for completion by the end of Januray.  The plan should identify the areas and homes at risk, mitigation measures for home protection and access and be able to provide resources – from sandbags to pumps to portaloos.

South Galway Flood Relief Committee met with Galway County Council and Cllr Joe Byrne for an inital review of this proposal and we were happy that there was good progress being made here and will await final plan in the coming weeks.

-David Murray



Flooding in Grannagh, Blackrock and Skehanna

This article covers some of the flooding scenarios within the Ownshree catchments where the communities of Roxborough, Castleboy, Grannagh, Blackrock and Skehanna are vulnerable to flooding.

Location and Hydrology

This area that we are focusing on is mainly the area west and south west of Loughrea, along the main Loughrea to Gort Road.  The main river flowing through this area is called the Owenshree river which makes it’s grand appearance flowing under the Seven-Eye Bridge close to Kilchreest.


The Owenshree river is part of 3 main rivers in the Galway Bay South East Catchment and this area in particular is called the Kilchreest Catchment which is sourced from the North Western region of the Slieve Aughty mountains. It can flow as close to 1km from Loughrea lake but will eventually end up in Kinvara bay (Note : Loughrea and easterly Slieve Aughties drain into the Shannon)


The following diagram shows the profile of the river flow from Slieve Aughties to Kinvara and you can se that Blackrock is at the end of a land-locked basin but has underground connectivity.


Some of the main areas within the downstream catchment are Kilchreest, Castleboy, Grannagh, Blackrock and Skehanna.   The main upstream sources are Sonnagh, Gortnamannagh, Killeenadeema and lower Glenaclara


The area of the main sources of the Owenshree river is Sonnagh and one of the highest sources is Lough Belsrah which has a Windfarm (Sonnagh) located next to it.


Lough Behsrah is an unusual lake located in a valley with steep sides and supposed to be quite deep.  Its about 500m Long and average of 50m across.

Lough Belsrah (Courtesy of Marco Leen)

Lough Belsrah and small channels from the windfarm flow downstream and are joined from small channels from Gortnamannagh and flow toward the ‘Soldiers bridge’

Stream coming down from the Sonnagh windfarm

The Sonnagh, Gortnamnnagh areas represent a significant portion of the uplands catchment and these flow to the Soldiers bridge in Gortnamannagh.owenshree2.JPG

There are also areas of Killeenadeema and lower-lying Glenaclara that flow into the Owenshree river and this flows north-west under the Seven-Eye bridge at Kilchreest.

From there the river changes direction from north-west to south-west and heads parallel to the Loughrea-Gort road toward Castledaly and Peterswell.   It first flows through Roxborough (Lady Gregory’s birthplace) ruins and past the old stewards house.  From here the river flows into  Isterkelly and Castleboy where it disappears into swallow holes in the streambed in Ballybackage.  There is connectivity between these swallow holes and to the Coole Demense river rising.

In a normal summer the river fully disappears into the swallow holes and in fact in a normal winter this can be also be the case.  When there are heavy winter rains, these football type of swallow holes overflow downstream into Blackrock Turlough which rises and flows through a number of small swallow holes.

Blackrock Turlough

Blackrock Turlough is located on the left side of the N66 between Gort and Loughrea close to Peterswell.


In heavy winter rain, it can rise significantly.

Courtsey of

Blackrock can contain a significant amount of water in wintertime e.g. 4.1 million cubic metres (2006), 4.0 million cubic metres (2007) and 2.47 million cubic metres (2008) and can rise to depths of over 12 metres in some places [1].

One thing about Blackrock is that it’s regarded as a flashy Turlough as it is one of the closest to the Slieve Aughty Mountains – After heavy rains, in over 36 hours, Blackrock Turlough can rise over 10 metres and extend over 2km.

A single night’s rain can cause Blackrock Turlough to rise (Courtesy : Sean Brady Aerial Photography)

Blackrock Turlough swallow holes have a significant connectivity into the underground river system. The connect to neighbouring Lough Coy and Ballylee and can connect to Kinvara east (close to Dunguaire) and Kinvara Central springs (Pier).

blackrock turlough connectivity

Blackrock connects underground to its close neighbour Lough Coy which then connects to the Ballylee (Ballycahalan  river) and in severe cases, the depth difference and pressure between Blackrock and Ballylee is great (>10m heights) that one of the Ballylee swallow holes starts to reverse and become a rise (Also known as an estevelle) .  The following diagram shows a conceptual model [1] and the type of connectivity from mountain to sea.


Severe Winter Flooding

As we have seen on many previous blogs, in normal summers and normal winters, these underground systems work perfectly.  Here is a snapshot of the height over 3 years. [1]


Another way to look at Blackrock is to look at average inflows and outflows and in the above period in ‘filling phase’ is we can see an average inflow to Blackrock is 10m3/S while at the same time it’s outflow is just on average 2m3/s [1].  Therefore, if the 10m3/sec inflow is sustained over a prolonged period, the Turlough fills and starts to become a flood risk.

When you get severe winter rains in the Slieve Aughty mountains, the small swallow holes that can normally sink 2m3/s cannot handle this and like a basin the Turlough levels start to rise,  leading  to significant flooding.  While the maximum volume of Blackrock Turlough in Sept-2006-Sept 2009 as 4.1 Million cubic metres of water, in 2009 the volume reached of 15.9 Million cubic meters at its peak and covered an area in excess of 3 km2.

This Turlough rose to close to 29 m and this caused significant flooding impacts. Here is a profile of Blackrock Turlough during the 2009 winter flooding. [1]


The level of Blackrock peaks around 29m because it then finds an over ground route which will be discussed below. Similarly with Lough Coy, once it reaches 17m, it will also overflow over ground.

Flooding Dynamics

There are 4 main flooding dynamics when the Owenshree catchment has high levels of rainfall.


These are as follows:

  1. Flashflooding in Roxborough
  2. Backup and flooding in Blackrock and upstream
  3. Turlough Overflow (Underground)
  4. Turlough Overflow (Overground)

These will be dealt with separately.

Flash-flooding in Roxborough

The first casualty of flooding happens around Roxborough.  The Owenshee river powers under the 7-Eye bridge and turns South-West and into Roxborough.


The river goes through a narrow bridge and then the river itself narrows and causes a restriction in very high water flows.  With rapid run-off the Slieve Aughty’s these restrictions lead to a water backup and this floods Paddy McGlynns home and farm buildings. Note : This house is a protected building constructed around 1820. (Details here)  and unfortunately floods to about 2ft of water

The area in Roxborough, close to the old Roxborough House which is prone to flash flooding (McGlynns home – Stewarts house inset)

The dynamics around flooding in Roxborough. The Bridge and a restriction in the river cause the water to back up and overflow into McGlynns – This only lasts for a few hours but floods a home and farm buildings.

As this is close to the Slieve Aughty mountains, the flooding is flashy.  The flood can come within a few hours and be gone 20 hours later. This type of flooding has happened several times over the past 20 years only.

Backup and flooding in Blackrock and upstream

When there is a large water volume coming down the Owenshree catchment (from Sonnagh, Gortnamannagh and Killeennadeema) then Blackrock Turlough can’t sink all of this water (coming on average at  and starts to rise. If the volume of water is too great then the entire area from Blackrock back to Grannagh starts to fill up. This causes flooding in Castleboy, Grannagh and around Blackrock


Here Blackrock Turlough has filled back as far as Grannagh and flood homes. Castleboy i
Looking directly west toward Blackrock. With Grannagh on right. Courtesy of Sean Brady Ariel Photography.

Eventually, if the water runnoff the mountain is voluminous enough, the Blackrock Turlough level reaches a limit (29m above see level) and overflows into Skehanna.

Turlough Overflow (Overground through Skehanna)

Once the level of Blackrock approaches 29 metres (above sea level) – then it finds a outlet close to Limepark house, beside Rahealy.  Some of Turlough is over 16m deep at this stage.

It overflows across the Skehanna to Blackrock road and flows through Colm Burke’s farmyard and in through the village of Skehanna causing severe flooding to the community.  It then makes its way to the Lough Coy overflow.

The devastation of the overflow close to Rahealy as it comes through Skehanna.
Blackrock expanding to threaten Coleman’s house (left of Centre). Courtesy of Sean Brady Ariel Photography.
Blackrock Turlough spilling over into Colm Burke’s farm yard. Courtesy of Sean Brady Ariel Photography.
The overflow contining into Skehanna and cutting off access. Temporary scaffolding is in place to help with access. Courtesy of Sean Brady Ariel Photography.
Capturing this from the other side,  with Blackrock Turlough in the background. the flow through Skehanna village can be seen here. Courtesy of Sean Brady Ariel Photography.

Blackrock Turlough Overflow (underground)

As Blackrock gathers a head of volume of water 16m deep in some places, it can put a significant pressure (underground) on the downstream system in Lough Coy and Ballylee.  It causes swallow holes to become springs. It causes Ballylee swallow hole north (Pollaleen) to  reverse direction and rather than being a swallow hole – it becomes a rise and water flows out of it (this is called an estevelle).  Blackrock overflow and underflows now pouring into Ballylee, through Skehanna and Lough Coy join with the the swelling Ballycahalan river and starts to flood the Ballylee, Deerpark and Rinerush areas.



There were several houses flooded in Roxborough, Castleboy, Grannagh, Blackrock and the Skehanna area in the 2009 and 2015/16 floods.

In Roxborough, 1 house and farmyard was flooded.  In Grannagh 3 homes, were flooded and 4 were badly threathened and 11 were inacessible and many septic tanks were flooded. In Skehana/Blackrock – 2 homes were flooded badly, 2 flooded but were protected (sandbags/pumps) and 3 were badly threathened.

Over 38 farms were affected in Grannagh, Blackrock and Skehanna and over 800 acres of farmland was flooded, many of these farms were flooded for several months. Over 10 farms were in accessible and 8-9 farmyard slurry tanks were washed out into the area.


In Castleboy, acces was limited from Castledaly.  In Skehanna and Blackrock 16 families were isolated and required a pedestrian bridge to get out. The following roads were closed:

  • Labane-Peterswell road closed for 50 days
  • Skehanna-Limepark road closed for 50 days
  • Skehanna-Peterswell road closed for 99 days

Overall, the flooding dealt a very serious blow to the communities of Roxoborough, Grannagh, Castleboy, Blackrock and Skehanna.

What can be done?

This area is one of the high-risk areas as it is so close to the Slieve Aughty Mountains and is very sensitive to changes in land practice.  There are real concerns that mountain land management, farming, forestry and windfarms have increased the mountain run-off over the past few decades. There are several potential mitigation measures including.

  • Slowing the flow
  • Flow Diversion
  • Underground drainage
  • Keep flowing

For slowing the flow, attenuation would attempt to hold water on the mountains.  There may also be methods to ensure mountain land management doesn’t overly accelerate water off the mountain e.g.. land drains, forestry drains, forestry roads, windfarm drains and roads.  There is a potential to use natural flood management techniques to slow the flow – remember a dynamic of blackrock is that normally it can only drain at 2m3/s to anything to slow the peak flows into is are useful.

Diverting the flow

One of the interesting things about the Owenshree river (which can rise 1M in 4 hours),  is that soon after the Seven-Eye Bridge close to Kilchreest where the river swings left (west) it is only a few hundred metres from the source of the Aggard. Here it is in the red circle below:


This means that there is a potential solution to be able to divert some of the Ownshree into the Aggard. This solution has been details in an OPW report Termon Mannin Kilchreest Final Report 231210.  This solution is feasible, but only on the back of delivering an improved drainage scheme on the Dunkellin river which is currently being developed.  Temporarily alleviating some of the flow from the Owenshree river would lessen the build up of water on Castledaly, Grannagh and Blackrock and be an overall benefit on the whole South Galway flooding.

Protecting from flash flooding

Once the water is travelling unders the 7 Eye bridge – It’s almost at full flow and there is no stopping it on its way to Roxborough toward Blackrock.  An obstruction (Bridge and river narrowing)  holds water back but floods McGlynns as the river is very close his house.  Could the house, farmyard be bunded?  Could the bridge be increased? Will it have an impact downstream?  It will have to be analyzed by our hydrologists but it seems very reasonable to try to protect a house that is threatened by water for a several hours, after which things are back to normal again and that extra water is already in the Blackrock Turlough.

Underground Drainage

Blackrock Turlough is the farthest from the sea and it becomes more challenging to drain off additional water through the current system, particularly where there are 2 other rivers into South Galway system that have flooding dynamics.  From talking to locals in the area, I’ve heard rumors that there were some river diversions on the Owenshree river many years ago, something to do with Limepark house. If you check out the 1836 OS map here and move the OVERLAY Slider and you can see the overlay of then (1936) and now  and you will see a river appear and disappear


These (and other) swallow holes may be covered but it may be possible to clear some out so they can sink their maximum flow.


Another dynamic that could be investigated is the results of keeping water flowing downstream. For instance if Coole Lake has a more streamlined outlet to the sea that stops it reaching 15m (over sea level) then in theory Kiltartan and Ballylee will flow better and this would have an impact on the underground flow from Blackrock. It’s hard to say how much this would be but it would probably not be major.  Hydrology experts are currently studing these effects and will be able to give a scientific answer.

Overall the flooding mitigation of these communities is a high prioritiy for the South Galway- Gort Lowlands floods scheme and the design consultants will be tasked with coming up with solutions designs within the next 18 months.



A huge credit goes to Own Naughten, Lawerence Gill and professor Johnston who have done a lot of studies around the South Galway Area.  The Turlough data and some concept images were taken from the following paper

Also big credit to Sean Brady, from Sean Brady Aerial Photography as his flooding images captured from his drown have really helped us tell the story of South Galway Flooding

Thank to Tommy Fahy for details on Grannagh

Thanks to Pauric Collins and Colm Burke for providing details on Skehanna and Blackrock.
-David Murray