Templemore History

The town of Templemore, Co. Tipperary, lies on the River Mall, which drains a catchment area of 22km2 that includes parts of the Kilduff and Devilsbit Mountains, before flowing into the River Suir two kilometres further downstream. The town has a long history of flooding, with a number of events having been reported over the last 150 years. The most significant of these occurred in December 1968 and, more recently, the November 2000 flood inundated approximately 40 properties.

The Office of Public Works (OPW) was requested to address the flooding problem and, in response to this, the OPW flood relief section’s design team undertook a pre-feasibility study that involved a preliminary investigation and an assessment as to whether a flood relief scheme for the town was likely to be technically achievable and economically viable. The study found that such a scheme was likely, and so a full feasibility study and outline design of alleviation options was then undertaken and those findings brought to Public Exhibition.

Following initial exhibition, an improved understanding of the flow regime (in particular, during both drought and flood conditions) drove some design changes. This study has shown that the properties upstream of Templemore belong to a separate flooding problem. These are now being treated as such under their own Minor Works Scheme where the Local Authority will be put in funds to implement their preferred remedial works.

The OPW Climate Change policy requires that a scheme is designed in a manner that, at a future date, defence levels or flow capacity could be enhanced at minimum cost and impact, should the expected change occur. In that eventuality, the cost of upgrading culverts is likely to be very significant. As such, it is both reasonable and practical to make allowances for Climate Change in culvert sizing at the time of scheme construction. The OPW national policy is to add 20% to the design flow estimate. This has been applied to the River Mall flood relief scheme where the 100-year design flow used includes for 20% allowance to produce a Climate Change flow estimate of 21.63 m3/s.

The design proposals to resolve the flooding issue that were exhibited in 2015 comprise the following:

• a 70m-long inlet channel starting in the Mall River just downstream of Abbey Cottage
• a new outflow from the lake to run under Blackcastle Road to the inlet channel
• a defence line north of the town with Debris and Gravel Traps and a small Drop Weir

River relocation by constructing a new 750m long channel (with a 7.5m base-width) that begins in Shortt’s field and finishes 230m downstream of Small’s Bridge.

The scheme was confirmed and construction began in June 2017 by OPW direct labour work force.

As the new river channel will operate all the time, its Environmental needs are different to those of a traditional diversion, and in order to aid fish passage, there are no long culverts, unlike the proposals exhibited in 2009. The bypass river channel design includes for a two stage channel where low summer flows are contained within a narrower sub channel called a thalweg. Many biodiversity and environmental enhancements were included within the footprint of the flood relief scheme extending to over 2km of channel length. These measures, all 160 have been GIS mapped to allow for future monitoring and maintenance of same. Arising from the success of these enhancements within their surrounding environment, the scheme was shortlisted for two national awards:

• Association of Consulting Engineers of Ireland Awards

-Sustainability National Environment

• Irish Concrete Society

-Environmental Initiative – Sandmartin Wall

It is currently anticipated that substantial completion for The River Mall (Templemore) Flood Relief Scheme will be achieved prior to the end of 2024. Ultimate completion will be subject to favourable weather conditions and third party agreements, which are being progressed by the OPW.