South Galway Flood Relief Scheme Update Nov 2018

Galway County Council  organised a project update and presentation to the key community stakeholders on Nov 9th.   There are positives and negatives. In general SGFRC is happy with the team work, the professionalism and world-class expertise being brought to the fore here but concerned over environmental risks and the impact of 8-10 month delays due to project complexity.

Summary

[South Galway Flood Relief Committee (SGFRC) Perspective]

  • There has been a huge amount of engineering and scientific work in ensuring we are getting the best overall solution for South Galway.   The model of the underground network and connectivity looks very good with <1% errors which means we have for the first time ever we have a tool to allow us to get a very good understanding of flow dynamics in South Galway. This means we can now predict flood events probability and extend  as well as provide the best assessment of flood solutions
  • We are very confident that we have a superb overall team including Galway County Council, OPW, Ryan Hanley, Mott McDonald, GSI and TCD.  There has been a lot of proactiveness between the entire group to ensure the project progresses and we hope that this will continue.
  • We are happy that some advance works are progressing especially finding an alternative access to Rinrush where 10 families have been cut-off for many weeks at a time.
  • The engagement with the public is quite good. The engineering and environmental consultants have taken our communities feedback into account and are actively looking for answers

However, the following are the key concerns

 

  • We are concerned that this project will be threatened by environmental factors, even though this is project should improve people lives And the environment. This is quite concerning. We have to ensure that Target Maximum flood levels across the catchment are based on people’s health, homes, farm buildings and roads and are not dictated solely be environment.  If feels like we are navigating through the eye of an environmental needle at the moment.
  • We acknowledge that this is an extremely complex project and there have been additional works being done based on public consultation feedback, we are concerned about the overall impact to the timeline.  The complexity delays could add an additional  8–10 months onto the overall schedule and this is very difficult to accept as we have an open threat of flooding every winter.  In the interim, we are not confident that Galway County Council can provide the right level of flood support as the emergency plan is not realistic. We need to understand how we can improve the timeline

 

 

Meeting Details

Attendees

  • Enda Gallagher :Galway County council
  • County Councillors : Joe Byrne and Michael Fahy.
  • Johnathan Reid , Conor Warner, Michael Joyce : Ryan Hanley Engineering Consultants
  • Rita Mansfield : Mott MacDonald , Environmental Consultants
  • Ted McCormick , Owen Naughton: GSI
  • Patrick Morrissey, Paul Johnson, Lawrence Gill, TCD
  • David Murray, Martin McInerney, Michael Cahill, Ray Fogarty, Tommy Fahy (South Galway Flood Relief Committee)
  • Diarmuid Kelly, David Krause : Cuan Beo
  • Mattie Hanlon

Engineering Update

Engineering input to date

Data collection for the study area ongoing and large bank of information has been collected and reviewed.

8 weeks surveying maximum flood levels, gathering all information required for flood risk assessment.  Note : Survey not complete (See additional note below)

  • Ongoing engagement with TCD and GSI regarding modelling.
  • Additional LIDAR areas were identified. LIDAR Survey is now complete. Data to be issued in the next few weeks.
  • Majority of Meetings with committee members / area representatives to identify properties complete. Meetings to be completed once all LIDAR mapping received
  • Site walkovers carried out to flood risk areas. To be completed once all LIDAR mapping received
  • Threshold survey for properties in or adjacent to be flood risk areas (based on Winter 2015/16 and November 2009 flood extents) completed.
  • Culverts and bridges survey completed. Additional topographic survey to be undertaken for particular sections.

Notes :

  • There are place where house surveys have not been completed. This is because the LIDAR Data was not available. All LIDAR Surveys have been complete but the data processing is still ongoing and will be available in the coming weeks. Once this has been done the additional home surveys will be complete.   This includes areas around Kilmacduagh, Tarmon, Tulla areas.

Public Consultation

Public Consultation held on 3rd May 2018 in Gort. The two main themes emerging from the public consultation included

  1. That effects of rapid-runoff the Slive Aughty highlands and the effect this has on flooding
  2. Concerns that the scheme would affect salinity in Kinvara Bay

Based on feedback from Public Consultation, the following has been completed:

  • Two site visits with Committee to the Slieve Aughty to forestry lands and windfarms.
  • Assessment of the benefits associated with potential works in the Slieve Aughty ongoing. TCD has undertaken modelling and prepared a report on the findings.
  • Assessment of coastal discharge ongoing. Additional dye tracing proposed to confirm the catchment area planned to undertaken in the coming months.

Advance Works Assessment

Possible Advanced Works contracts identified as follows:

  1. AW1: Reinstatement of blocked Swallow Holes. Meeting held with NPWS was held. Not permitted as this is difficult to understand the impact. No longer to be considered for Advance Works.
  2. AW2: Culverts between Caherglassaun and Cahermore (at Leeches) . Likely significant works. Insufficient information available yet to design. On hold until main phase.
  3. AW3: Cahermore to Kinvara Overland Flow-path Reinstatement Measures. Insufficient information available yet to design. On hold until main phase.
  4. AW4: Newtown Hill/ Rinrush Emergency Access Road. Works being considered for advanced works. Assessment complete and proposal developed. GCC to confirm if works are to be scheduled. Next stage once proposal is finalized is landowner engagement.
  5. AW5: Roxborough Demesne. Works scheduled to be undertaken as part of the Kilchreest Drainage District maintenance works. Assessment complete and proposal developed. Works scheduled.

 Route Corridor & Target Flood Levels

  • Potential Route corridors for flood alleviation measures have been identified to guide the environmental assessments and modelling. This identify the probable routes that conduits could take and involved site walk, LIDAR data and old mapping data.  There will be further refinement of these routes following TCD model inputs and additional LIDAR.
  • First Stage of Target Maximum flood levels and flood extents maps have been assessed for the Coole system based on threshold survey and site visits. This is an Iterative process and will be refined at later stages

The following table outlines the potential flood reduction

First Stage of Target Maximum flood levels
Name Previous Maximum Target Peak Reduction
Blackrock Turlough 29.45mOD ~2.5m
Ballylee 19.4mOD ~2.0m
Kiltartan 15mOD ~1.5m
Coole 14.75mOD ~2.3m
Caherglassaun 14.5mOD ~3.5m
Cahermore 13.6mOD ~3.3m

Notes : For Ballylee,  reduction of 2 M will not provide full protection for Ballylee Castle,  it doesn’t seem possible to physically reduce that level of water levels down fully. However they can be reduced to an acceptable level and with barriers to protect the doorways, it’s possible to manage the flooding. (Barriers have kept out rising levels recently)

Environmental Consultant Update (Rita Mansfield Mott MacDonald)

Rita reassured the group that her and Mott MacDonald’s role here is not to be the environmental nay-sayers (my words) but to successfully navigate this project through the necessary process so that it stands up against any environmental law scrutiny (Just think of Galway Outer Bypass being stalled for years as one of the environmental factors (bog Cotton ) was overlooked!

Work to Date

  • First Public Consultation: 3 May 2018 in O’Sullivan’s Hotel, Gort
  • Constraints Study: Completed August 2018
  • Report and Appendices available for download on http://southgalwayfrs.ie/
  • Ecological Field Survey (channel concepts): Completed August 2018
  • Advanced Works, Rinrush and Roxborough: EIA and AA Screening Completed November 2018
  • FRS Screening for Appropriate Assessment: Ongoing
  • Salinity Model: Ongoing

Notes :  Due to delay in the Catchment Model (TCD), there was a high risk to meet Eco field study.  Ryan Hanley developed a channel concept that allowed the majority of the Biodiversity, ecological sturdy to be done without missing a season (essentially a year!)  This allowed MM to have early understanding – come up with initial assessments ad to make sure we are not damaging vulnerable habitats

Public Consultation

Statutory Consultees (e.g. NPWS Coillte, etc)

Contacted by post in April 2018

  • Targeted meetings held with NPWS, IFI, Coillte, Forest Service, Local Authority Water and Community Officer
  • Key Outcomes:
    • IFI highlighted the importance of Kinvara Bay as a fishery and aquaculture area
    • NPWS raised concerns about swallow hole clearance possibly forming part of the Scheme. Proof of no significant effect would be extremely difficult as the response of the turlough to the works could not be predicted. The potential for such works to have to go to IROPI is high.
    • The potential for these works to fall under the remit of “management of a European site” was tabled. NPWS stated that this would not be applicable as the turloughs were still operating as turloughs, and as such are acting naturally.

Non-Statutory Consultees (e.g. NPWS Coillte, etc)

Public Consultation day held 3rd May 2018 in Sullivan’s Royal Hotel, Gort, from 3pm to 10pm

Key Outcomes:

  • The perception from the public is that something has changed in the catchment in recent years requiring the need to slow the flow in the upper catchment.
  • Concerns about the possibility of an overland flow path between the turloughs and the sea: reduction in available areas of land for farming, change in salinity / water quality of Kinvara Bay affecting aquaculture.
  • The flood relief scheme may not resolve flooding of access roads and may not protect against land flooding (scheme directed towards property protection)
southgalwayfloodingcontraints.JPG
Public Opinion on Source of Flooding
southgalwayfloodingcontraints2.JPG
Public Opinion on Measures

Constraints Study

There was study done regarding the environmental constraints that potentially affect this development.

These constraints are built into any proposed development project and the role of the environmental consultants (Mott Macdonald) is ensure a really thorough study is undertaken to minimise the that this project won’t be scuppered by environmental issues at a later stage. (Think Galway outer bypass delay of > 7 years)

As this area is peppered with SACs then this is quite a complex part of the project and includes studies on :

  • Biodiversity – change in turlough hydrology, damage to protected habitats /species
  • Cultural Heritage – avoid National Monuments, recorded archaeological monuments and protected structures
  • Landscape – landscape character areas, stone walls and hedgerows, enhancement
  • Soil Geology and Hydrology – alter drainage patterns and geological features
  • Water Resources – water dependent activities, WFD,
  • Population and Land use – interruption to services, value of tourist attractions
  • Material Assets – maintenance of transport and utility infrastructure

As this is a flood-relieft project – From the constraints study, the main focus here is the biodiversity/ecology. The main risks found were:

  1. Ballynastaig Woods – A channel could potentially have to be developed within area of wooded limestone pavement protected under the Coole-Garryland Complex SAC – High IROPI Risk (see below)
  2. Culvert at Lough Mannagh is a bat roost. The culverts at Hawkhill Lough could not be surveyed due to H&S, however have high bat roost potential. Channel Maintenance proposed, section of which is within East Burren Complex SAC
  3. Salinity of Kinvara Bay

Notes :

  • #1 is one of the main risks to the project and needs deep assessment. The route through the limestone pavement in Ballynastaig  will need to be assessed to see if alternate routes exist, or if it’s possible to have a different sized channel. This will be analysed and refined further when the TCD model is up and running (December 2018) . The Model will also help gauge the impact of reducing the max peak of Caherglassaun (3.5m) as the underground channel between Coole and Caherglassaun will probably still be in flow .
  • This will also link in with the Cost-Benefit
  • IROPI = imperative reasons of overriding public interest and is way to proceed with a develompent despite environmental constraints – however this is potentially a lenghty and costly process – so best to avoid!If IROPI is required – it would add years to the project

In general, they are the key areas. There were studies done for other mammals also but nothing high-risk

  • No real badger activity as these turloughs flows (so its not surprising)
  • Lesser horseshoe bat in Kiltartan Cave – need to assess impacts as we may be removing hedge rows in the vicinity for better water flow

Notes : DM stated that flood mitigation will offer more protection than the displacement of a few hedgerows. Feedback was that this was low risk.

Salinity Model

  • MSN Hydro International Ltd: Professor Mike Hartnett and Dr. Steve Nash.
  • Using an existing 3-dimensional barotropic/baroclinic model of Galway Bay which was developed using the INFOMAR data
  • The model has been validated against tidal dynamics and against acoustic doppler current profiler (ADCP) measurements at points within Galway Bay
  • The model will consider differences in horizontal gradients of salinity and also consider vertical salinity differences with and without the flood relief scheme
  • The model will use salinity base-line  data provided by Dr Rachel Cave NUIG
  • Data provided by EPA from 2008 to 2017 is also available to validate the model
  • Cuan Beo has indicated that they also hold salinity data
  • Marine Institute intend to put new monitoring station in Kinvara, this will not be available in time for the project

Salinity Concerns

Cuan Beo highlighted their concerns again for salinity affects in Kinvara Bay and that oysters cannot survive low salinity levels for long as it increases their stress and makes them more susceptible to disease.   SGFRC member Tom Fahy highlighted that there are risks to human lives and wellbeing by the levels of flooding in South Galway Catchment.  SGFRC Chair, David Murray reiterated that while this may be the wettest 2 decades in the past 300 years,  The South Galway communities should not become the dumping ground for excessive flood water run-off.  He highlighted that the Targeted Maximum flood levels were the vital contract to eliminating flooding threats to people’s homes and livelihoods while at the same time maintaining the integrity of the turloughs. 

GSI – Update

There has never been more data collected w.r.t. turlough monitoring and flood mapping in Ireland and much of this is in South Galway where many permanent monitors are being installed.

Current Monitors

 

 

GSI are also using Copernicus Satellite data ( 4 photos in 6 days) to look at historical flood data (e.g.  2015/2016 floods have been captured for the entire country). These are Radar images and can see through cloud.

These images are being analysed to and approximate the Turlough boundaries. The accuracy is 10m but it can be possible to get accuracy by averaging the boundary.  With the LIDAR data is it is therefore possible to get very good accuracy of the change in Turlough Volumes – which is essential for the Catchment Model.  There is very good accuracy compared with the turlough monitors except in areas of heavy woodland where it is difficult to gauge flood boundary from satellite data.

GSI are also developing rainfall simulations

  • 3 year accurate
  • 40 year historic
  • 1000 year synthetic (estimated)

gsi_rainfall_models.JPG

This will also take Climate Change modelling into account.

Catchment Model Updates :  Patrick Morrissey,TCD

There is no doubt that this is a very complex process.  A previous model developed South Galway Turlough networks was used as a based and then further developed into a flood analysis model.  The model was calibrated to achieve more accuracy by:

  1. Getting more precise data on whole topography (From LIDAR)
  2. Getting more historic flood data (From GSI)
  3. Focusing on key areas (From Ryan Hanley, Mott MacDonald)

Currently the model is now exhibiting similar behaviour to real flooding events e.g. generally <0.5% error for majority of areas. This has taken a lot of work to get this accuracy.

south_galway_flood_model.JPG

Running historical rainfall figures, this model has successfully shown the main flood events over the past 30 years. This model will now be used by RyanHanley to understand 1:100 flood extend to feed into Cost-Benetif analysis as well as being used to model and assess flood alleviation scenarios with Ryan Hanley

Patrick used the model to assess impacts of increased run-off the Slieve Aughty Mountains. He assessed the forestry coverage in the 3  catchments and the effects of thinning, clear-felling and maturity of sites.

forestry_analysis.JPGHe simulated various scenarios where he smoothed the peak events over 24 hr, 36 hr and 48 hr and reduce levels (storage).    In general, the effect of rapid run-off while it definitely has an impact, the overall flooding effect on the lowland Turloughs was not deemed substantial.  This can be related to Mature forests >15 years have a dampening affect on flooding.  With what was described as a very unrealistic case (store flood peak for 2 days, the effect on Coole was to reduce peak flooding it by 70cm.

Notes:

SFGRC stated that 70cm could mean a house flooding – Patrick highlighted that this 70cm was a very unrealistic case and was just there to give an indication – it was probably more likely a lot less. He did say there definitely has an affect but in the overall flooding of South Galway it substantial enough to merit investing in.

Conor Warner highlighted that the main basins provide the dampening effects.  An average of 8mm over 25 days is ok for Coole lake levels, but an average of 12mm over 25 days, there is serious flooding. This is the kind of timespan that we are looking at.  Conor also pointed out that we could blow out budget trying to manage the high-lands but we’ll still hit the same flooding scenarios. We need to invest in keeping the water flowing through the system and not letting it build up.

SFGRC summary :  I think this has shown us where our solution should focus.   We have seen the numbers that we need to reduce peak Turolough levels (2m-3m) and reducing mountain peak flows by 24-48 hours is not having this much impact so we need to see what  solutions we can have in the lowlands to manage levels (over several weeks). We saw in fact in, in Winter 2017 the flood levels rise with just continuous rain over several weeks.

We should not forget though that forestry felling has an clear impact so we need to ensure that this is managed properly and that the impact is mitigated.  SFGRC has worked with Irish Forestry Service and Coillte on a policy for the management of the Slieve Aughty forestry to minimize impact.

There was also a mention of a previous proposal where some portion of the the Owenshree could be diverted into the Aagard. Again, this was deemed a lower priority solution than keeping the water flowing through the Gort/South Galway lowlands.

Going Forward

The focus will be to now start using the hydrology model and running the 1000s year rainfall scenarios to understand the real one in 100 year flood event (there is speculation that we haven’t actually seen one yet) .

hydrology model

The corresponding 1:100 year flood will define the true flooding extend and give an estimate of the benefit of fixing this 1:100 year flood event.  this is the budget.

The consultants will then try different scenarios and measure these with the same data to test there efficiency and then try and match the cost and the environmental considerations.

Unfortunately, this level of analysis is more complex than anticipated and the feasibility study conclusion will be at least 8-9 months doing this analysis – Q3 next year (Sept-Oct 2019)  – However – the SGFRC would prefer that we get all the facts and accuracy we need here and develop the right solution rather than cutting corners and ending up with a sub-optimal solution.

-David Murray

Advertisements

One thought on “South Galway Flood Relief Scheme Update Nov 2018”

  1. Thanks David for keeping us informed. This latest update will take a while to digest but without your updates we would be totally In the dark . Long may you continue working on behalf of the community. Thanks Bridie Willers

    Liked by 1 person

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s