Why hasn’t Gort town flooded?

A question that I’ve heard asked a few times this winter is why Gort town didn’t have any bad flooding this time around. With water levels already higher then their 2009 equivalents, in most areas of the Slieve Aughty catchment area  – how come there was none of the panic in Gort town like there was in 2009?  Crowe St. didn’t need the big pump that was purpose bought. So what’s the difference – not much really – Let’s first start with an overview of the river system around the Gort area.

The River system in Gort

If we take the river system in Gort and trace it’s path to Coole we get a picture like this.

 

The Gort river is sourced in the Slieve Aughty mountains as the Owendalulleegh river. This river flows through Derrybrien into Lough Cutra when then flows out as the Beagh river. This river ends very abruptly in an area called the Punchbowl, flows underground and rises again as the Cannahowna river. It then flows through Gort, under Gort bridge, past the old Mart (ALDI)  and out through Kinincha into Castletown.  At Castletown the river sinks underground in a swallow-holes (Polltoophil North/South).

The river rises again in Kiltartan (200 M behind Kiltartan Church)  in Polldeelin, and flows for 600 m before going underground again under Coole Ridge (and new M18 Motorway) . This rises in Coole and flows as Coole River into Coole Lake and then flows 8-11 km to the sea underground from there.

Ballylee River

Unfortunately Gort is not the only river to flow into Kiltartan and this is where trouble can start brewing.  The Ballylee river also flows underground into Kiltartan as shown below:

gort2

The Ballylee river starts off as the Boleyneendorish  river in the Slieve Aughty mountains and flows close to Cloone and then into Ballylee (past the Castle) where it flows underground at Pollaleen.  The Ballylee river rises  into Kiltartan at Polldeelin and Pollnacapall. Note There is also linkage to the river at Kilchreest along this path.

Heavy Winter Rains – Tension in Castletown

Heavy winter rains bring a lot of issues around the Kiltartan area as there are now many competing water flows from Gort (Via Castletown ) and Ballylee.  In 2009 the underground channel into Kiltartan was at full capacity but the big issue came  when Ballylee river could no longer sink fully underground and flowed overground into the Castletown are (through Deerpark) . This flow was competing against Gort river for the Castletown swallow hole which then couldn’t sink all the flow so levels rose, and rose and rose in Castletown until they found an outlet across the N18 and flowed overground into Kiltartan.

watefall
Overflow from Castletown, into Kiltartan

This rise in levels had an unfortunate impact on Gort and Castletown levels backed up into Kinincha and Gort at LIDL, Crowe St, etc. This can be seen in the picture below. The red-roofed building is LIDL

Gortflood2
Flooding in Gort backing up fro Kinincha/Castletown. LIDL is the red-roofed building

The forgotten culvert

After many days of water flowing over the N18 road,  a part of the Kiltartan slip road collapsed and unblocked a hidden culvert.  Once this happened water churned through the culvert and the levels of Castletown dropped rapidly.

gortflood
The existing culvert under the N18 road that had not been maintained

This culvert hadn’t been maintained for years and had been heavily blocked. After the winter of 2009, this culvert was replaced with a brand new one and (3Mx2M) and with the massive rainfall throughout December 2015, this culvert was tested.  Here is a picture of it running at high capacity.

gortfloodings
The new culvert working under the N18, keeping levels down in Castletown

This short clip also shows the flow:

 

There were probably other contributing factors (improved flow through town, clearing river) but enabling the Castletown level to flow under the N18 at Kiltartan, rather than forcing it to flow over, is the key factor for  Gort town not experiencing flood difficulties this winter. It’s sometimes the simple solutions that can solve the problem!

Another key but more subtle dynamic in the South Galway drainage systems is the level difference between swallow holes.  If the levels of Kiltartan rise significantly then the pressure through the swallow holes at Castletown and Ballylee will drop, resulting in  levels rising significantly there and threatening to flow overland.

Keeping it flowing

It’s great to keep the water flowing but we also need to conscious about what happens further down stream.  Kiltartan still remains a pinch point in the overall Slieve Aughty drainage and adding this flow to already saturated system has rendered some of the new culverts in Kiltartan incapable of for maintaining efficient  water flow.  Levels at Kiltartan rise and make the upstream swallow holes less efficient.  Downstream, efficient flows are also challenged by the new M18 motorway construction and inefficient culverts at Raheen which have caused severe problems this winter. These river systems need to make it into Coole as efficiently as possible and then from there into sea at Kinvara.

-David Murray

 

 

 

 

 

 

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12 thoughts on “Why hasn’t Gort town flooded?”

  1. The reason why GORT flooded in 1995 and did NOT flood later on in 2009 or 2014 or 2015 in WETTER conditions is because one of the underground channels was blocked by a silage bale or similar debris in 1995.

    Local farmers ALONG the overground sections of River from around Lough Cutra to around Ballinderreen should be encouraged to

    1. Cut dead branches off trees and remove from riversides in case they break and flow into swallowholes and trap debirs.
    2. Maintain minimum drain/riverine bed DEPTHS on or beside THEiR land.
    3. NOT store silage bales near the shaggin river any more. 🙂

    This of course means that not only are farmers not discouraged from maintaining drainage but that they are agents of the state (OPW) as long as they follow the clear instructions on bed minima,.There are no migrating fish in the river sections as they will not swim in the dark. The OPW themselves should survey the UNDERGROUND sections around once every 5 years and deall with blockages in the underground sections…if any…during the spring/summer when levels are low.

    Let the OPW deal with those utter morons in the NPWS to save putting years on people and get a LONG term maintenance PROTOCOL agreed from Ballinderreen to Kilchreest and south towards Tubber.

    Water has backed up as far as Kilchreest at this stage, never mind just Kilternan. Over 100 square miles is affected.

    If that happened in Dublin then Simon Harris would be told to live in a caravan in a field in the middle of the flood to get it sorted what with the election coming up. 😦

    Liked by 1 person

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