South Galway Flooding – Tierneevin/Kilmacduagh

I recently called out to the community around Tierneevin and Kilmacduagh, Hawkhill etc. to get a snapshot of flooding issues that they had there and ‘try’ and make sense of what was happening.  In previous presentations I’ve mentioned that the area flooded but I had a lack of knowledge of finer details of the area, a fact that a certain Mr Dermot Flaherty brought to my attention on a fairly regular basis  – To thanks to Dermot for enlightening me on the dynamics and to the locals I met on the day. Thanks as usual to Sean Brady whose fantastic drone footage has prove such a valuable asset in capturing the extend and devastation of the flooding.

[Disclaimer – I probably walked through at least 15 townlands and 2 counties in about 20 minutes so if I didn’t get the exact location of the townland … apologies and if you’re from Termon but I said you were from Beagh, then sorry too.]

Most people would be familiar with this area beond the golf course, with the Kilmacduagh round tower dominating the skyline. In my flood maps to date, it’s the area that is shown in the circle below.

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The area of Kilmacduagh ,Hawkhill and Terineevin

Overview of drainage

From a drainage point of view this area can be seen as relatively independent of the Slieve Aughty drainage but they both have Coole lake as a common factor when it comes to severe flooding in the area.  The source of the water flow here comes from the Burren and mainly through Lough Bunny.

Lough Bunny is  a lake of about 2.5 km long and with a maximum depth of 14m.  It has no overground inflow or outflow. While most of the other lakes around Lough Bunny, have water flow that tends to flow south/west and are considered part of the River Fergus catchment, Lough Bunny has been associated in relatively recent times (1998) to the Kinvara catchment area (Also known as Galway Bay South East catchment).  Lough Bunny drains to the sea, mainly through Kinvara.

On the north shore of Lough Bunny (Closest to Boston Castle) , there is a swallow-hole/sink that re-emerges into Rockvale via a series of 3-4 springs as the Rockvale river. During summer season this flow may be very faint but with high winter rains this flow can be several M3/s. This is shown in the map below:

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The following are pictures of the springs in Rockvale (March 2016)

The Rockvale river continues to flow northward and it passes under an old stone footbridge (an old mass path).

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The old mass path and footbridge upstream from Lough Skeardeen

This continues north-east and flows under a road through 2 pipes and continues  into Lough Skeardeen.

During summer months this flow may sink into the ground to re-emerge ~200 m north east and flows into Lough Avatia. In severe winters this flow can be overground.  There are other springs emerging in Kilcorkan that also flow into Lough Avatia.

The outflow from Lough Avatia then flows behind Kilmacduagh castle and continues onward to Tierneevin as the Ballyhale river and it flows under a road again through 2 small pipes close to Heleberts house, the bridge serving at the boundary between Galway and Clare. It then flows into a seasonal Turlough called Lough Managh and then continues as the Cloonteen river under an old culvert close to Tierneevin church and on into Hawkhill Turlough.  During dry summers, this dries up completely.

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Overview of flow into Tierneevin/Cloonteen
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The area of Kilmacduagh ,Hawkhill and Tierneevin

There is another small flow originating from Cloonafunshin bogs (Polliffern lough) that flows north and into Coole, passing close to the Golf club and flows into the Coole Basin (Lough Nacarriga)

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Flow from Cloonafunshin/Polliffern flowing beneath R460 (Kilmacduagh road)

In typical summers, the overall flow is very minor. In typical winters the turloughs swell and there are flows of several M3/s under the culvert at Tierneevin.

Swallow holes

There are several swallow holes in the area.  There is one, noted in GSI surveys as the Cloonteen river sink (close to Helebert’s house)  which has been analysed and shows a lot of connectivity (17 links) to the Coole system and Kinvara. According the tracer dyes it has the following connectivity

  • Corranroo West Spring (minor flows)
  • Caherglassaun (Extremely rapid flow rates)
  • Coole North rising (Extremely rapid flow rates)
  • Gort/Kiltartan River (via Cannahowen?) (Rapid rates)
  • Pollbeaghy (Extremely rapid flow rates)
  • Loughcurra (moderate)
  • Moran’s cave (Rapid rates)
  • Pollaloughabo Cave (Rapid rates)
  • Coole South Rising (Extremely rapid flow rates)
  • Kinvara West and Central (Moderate flows)
  • Quinn’s Cave (Extremely rapid flow rates)

Overall, this swallow hole is of major significance to the area as it has substantial connectivity. There was/is another swallow hole to the north beside Carr’s house but this may currently be blocked.

There is also another swallow hole is located at Cloonafunshin/Polliffern lough .

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Cloonafunshin/Polliffern Lough

Severe Winter flooding

In severe winter flooding (as in Winter 2015) the area got very badly flooded. The waters of Lough Bunny rose and gave more substantial flows into Rockvale and this wasjoined by other springs in Lough Atalia which prove too much for the culvert at Tierneevin.  The picture below shows Lough Managh turlough in the foreground with Tierneevin church on the very left.  Far off in the distance on the top-left you can see the outline of Lough Bunny.

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Severe flooding around Tierneevin

This can be represented by the picture below where you can see substantial flooding.

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The following superb drone video by Sean Brady shows the devestation of the floods

In particular around Tierneevin, Cloonteen many houses were under threat with the flooding and required sandbags and pumps to keep the water at bay.   Pumps were also used to pump water across the road at the culvert in Tierneevin.  The pumped water can be seen in the middle of the picture here with Tierneevin church in the lower centre left.

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Water Dynamics

The problem seems simple – the Tierneevin culvert (follow the tree line across the road)  could not handle the flow of water coming into it but there was another factor that affected this – the level of Coole Lake.

In this diagram the level of Coole lake can be seen on the left of the photo.  The levels had risen so much that Coole lake was backing up into Tierneevin (Similar to many other places). This had 2 major effects.

  1. It reduced the flow rate across the culvert
  2. It reduced swallow hole flow rates into the Coole basin

The levels of Coole lake effectively pushed back on the flow rates (overground and underground) coming out of Tierneevin. It was also Coole Lake level that flooded Flaherty’s farm in Tierneevin/Tawnagh West.

Solutions to flooding

There are a number of things to consider here but the #1 is the level of Coole lake. Coole Lake at the 2015 levels cause flows to back-up in Tierneevin. We’ve seen the same for Kiltartan also.

The #1 solution to solve Tierneevin flooding is to reduce Coole Lake peak levels.

Reducing Coole Lake peak levels will allow better flow through the culvert and will allow the swallow holes to function.

There are other items that need to be addressed.

  1. As there was still an overflow at the Culvert in Tierneevin, an additional culvert would be required beside the current one (or a new more substantial culvert)
  2. Swallow holes in the area should be cleaned to ensure they have maximum capacity during flood events. There are concerns that a swallow hole has been filled in, in recent times so this would need more investigation.

Other considerations

  1. There are currently OPW proposals to solve Termon fooding by giving it a path to Lough Bunny but as we have seen we need solutions for Tierneevin in place to enable this.
  2. The road in Tierneevin has been raised substantially and therefore limit any alternative flow over the road – Better culverts are needed to ensure that they match the more substantial winter flows from Lough Bunny.

 

While the flows are not as substantial as the flows coming from the Slieve Aughty’s there is still a significant flooding problem in this area that causes a lot of distress and the solution’s are within reach –  Keep Coole lake peak levels down and increase flows out of Tierneevin through swallow hole clearing and also better culverts.

-David Murray

 

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