Robert Grace and Tríona Doherty
The draft Shannon Flood Risk Management Plan was published last Friday (July 15 ) and has recommended expenditure totaling a little more €5.9 million on flood defences for Athlone.
The report investigated two viable options in terms of flood defences. The first option considered the construction of 2.03km in flood defence walls, 1.48km of new embankment, and 16m of floodgates.
The installation of a flood-forecasting unit to send warning messages when the water level reaches a specified trigger point, and targeting public awareness also form part of this option.
The report said option one would reduce the risk of flooding to 246 of 279 properties within the area identified as being at risk in a 1 in 100-year flood event, leaving 33 properties without defence. The report considers the flooding of 2015/2016 to be a 1 in 100-year event.
The second and now preferred option involves the construction of flood defences, the raising of road levels, storing flood waters, and a flood forecasting and warning system in line with that detailed in option one.
This second option incorporates the construction of 1.038km of new flood defence walls, 10 in total; one to stretch along The Strand to Wolfe Tone Terrace and others along the docks and behind Sean’s Bar. The longest of them all would be positioned around the Canal Walk housing estate located on the Clonown Road.
In addition eight embankments totaling 2.29km are proposed, including one running to the rear of Deerpark. This option also includes the construction of six floodgates totaling 16 metres and a storage area for water in Garrycastle designed to deal with potential flooding of the River Al.
It is believed that this option would reduce the risk to 251 of 279 properties, meaning 28 homes would not benefit. The plan says that the owners of these properties might want to consider “individual property protection” measures to safeguard their homes. The relocation of homes has been deemed unviable by the study.
A number of dredging options for the Shannon were also examined, but were rejected due to environmental concerns.
Four separate options involving dredging were found to be “technically viable” as they would have significant impact on water levels. These include the possibility of dredging the river channel between Lough Allen and Parteen Weir, resulting in a reduction in the level of the channel bed by 0.5m.
However, the report dismisses all of these options as “environmentally unviable”, as the majority of the River Shannon south of Roosky is designated as either Special Protection Areas (SPAs ) or Special Areas of Conservation (SACs ). These designations are mostly based on habitats or species which depend on the supply of freshwater for their survival - the report gives the example of alluvial woodlands in river floodplains, and ducks wintering on freshwater lakes.
These habitats and species could potentially be threatened by any measures that change the existing flooding regime, or introduce significant amounts of silt into freshwater environments.
The report in full is available for viewing on the website of the Office of Public Works at www.www.opw.ie/FloodPlans, and is currently open to public consultation.