Sunday 17 December 2017

Dredging is not the sole solution for Enniscorthy's flooding problems

By Amy Lewis

An artist's impression of what the proposed new bridge in Enniscorthy would look like.
An artist's impression of what the proposed new bridge in Enniscorthy would look like.
Proposed new bridge as part of flood relief plan for Enniscorthy

Calls to dredge the River Slaney in Enniscorthy have grown louder and more persistent since flooding hit 147 properties and brought the town to a standstill last Decembe.

As they witnessed scenes that seemed all too similar to those in years gone by, more and more people began to ask questions and demand answers. The predominant question, which was posed to members of Enniscorthy Municipal District Council as well as to Minister for Public Expenditure Brendan Howlin, seemed simple: Why don't we just dredge the River Slaney?

Though it may appear to be a straightforward solution, Project Resident Engineer for the Enniscorthy Flood Defence Scheme Larry McHale insists it is much more complex than that. Due to the tidal nature of the River Slaney, he said that dredging alone would be ineffective and is not the answer to the town's flooding problem.

'Dredging is only partly effective in reducing flood levels in Enniscorthy because the River Slaney is tidal up to the Enniscorthy Bridge,' he explained. 'Additional dredging below tidal waters is not effective in reducing flood levels because the dredged area becomes filled with the rising tide and is not available to take the flood waters.'

A small amount of dredging is incorporated into the Enniscorthy Flood Defence Scheme, which is currently at the detailed design stage. For example, the river bed under the Railway Bridge and the Enniscorthy Bridge will be lowered by up to three feet. This will help to remove obstructions to the flow of the river and improve the movement of any flood water.

However, according to Mr McHale, only when combined with other measures will the dredging be effective.

'The Enniscorthy Flood Defence Scheme will use a number of engineering measures to protect the town from flooding. These include river widening, dredging, a flood diversion channel downstream of the town, extensive flood defence walls and a storm water pumping system,' he explained.

'Another necessary measure is the incorporation of valving arrangements on the existing drainage outfall pipes to prevent backflow of flood waters from the river and a build up of storm water at the back of the flood defence walls.'

'All of these measures work in combination to protect the town. Dredging alone will not protect the town from flooding,' he added.

The high costs and environmental impacts of dredging have been thrown around as possible reasons for the resistance to carry it out.

However, whether or not these factors are at play, Mr McHale reiterated the main reason: dredging alone will not work.

Mr McHale and members of Enniscorthy Municipal District are eager for the public to be made aware of what the Flood Defence Scheme involves and want them to understand the reasons why dredging the River Slaney isn't the quick fix for Enniscorthy.

A new website detailing the scheme is soon to be launched and at the recent Enniscorthy District Municipal Council meeting, Director of Services John Carley suggested including the subject of dredging in the Q and A section. A plan of the developed scheme is due to be put on public display by summer and Mr McHale said that this will be 'vital' for improving the public's understanding of what it entails.

Mr Carley has also recently said he will request for representatives of the OPW to return to the town to speak with the public on the subject of dredging. In the meantime, Mr McHale said that he is happy to speak with anyone who wants to know more about the dredging issue or the scheme in general.

Wexford People

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