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SOUTH DUBLIN COUNTY COUNCIL

MEETING OF RATHFARNHAM/TEMPLEOGUE/FIRHOUSE/BOHERNABREENA AREA COMMITTEE

Tuesday, October 08, 2019

QUESTION NO. 8

QUESTION: Councillor Yvonne Collins

To ask the Chief Executive, in relation to the proposed Whitechurch stream flood alleviation scheme, what are the underlying causes of the flooding and could the alleviation be implemented by other measures such as dredging, so as to reduce the intrusion of the hard defences and preserve as many of the trees as possible 

 

REPLY:

Previous flood events in the Whitechurch catchment were recorded of mainly being the result of a combination of the following; blockages caused by trees and debris at vunerable locations such as bridges and culverts, run off contribution from the adjacent roads surface water network and insufficent capacity in the channel to contain flood waters. All of which are currently being addressed in the proposed scheme.

In relation to dredging, the Preliminary Options Report for the scheme proposed the option of dredging in certain areas of the channel but was not considered to be feasible, mainly due to the nearby presence of Japenese Knotweed where dredging could result in the unquantified spread of the knotweed, along with the possible sedementation issues that dredging may contribute downstream in turn affecting the important aquatic ecology of the River Dodder. Initally, another option that was considered to minimise the hard defences required was upstream storage but no suitable locations in the upper catchment could be found to accomodate this.

With an understanding on the impact that tree removal for the scheme will possibly have, full tree removal will be kept to a minimum and when removal numbers are established a tree replacement programme of planting two trees for every tree removed will be agreed in advance with SDCC Public Realm.