COMHAIRLE CONTAE ÁTHA CLIATH THEAS
SOUTH DUBLIN COUNTY COUNCIL
MEETING OF SOUTH DUBLIN COUNTY COUNCIL
Monday, December 14, 2009
MOTION NO. 15
MOTION: Councillor D. Looney
That, in light of recent major flood events and the likelihood of more frequent freak weather events due to climate change, the Manager provide a report on all lands currently zoned for residential or other purposes (a) alongside the Rivers Liffey, Dodder, Poddle, Camac and other rivers in the area of South Dublin County Council, and (b) in any other areas identified as subject to previous flood events, in terms of the risk of flooding,
REPORT:
A planning map of the County is attcahed which shows the main watercourses through South Dublin and for indicative purposes a 150m wide buffer has been highlighted which shows the relevant zoning as is currenlty proposed in the Draft Development Plan.
Liffey: The part of the Liffey in South Dublin does not present a significant risk to residential property, based on the maximum flows from Leixlip (116 cumec) during the regional flood event of 29/11/09. No flooding occurred and the tributaries, although high, did not cause significant flooding either. It should be noted that the flow in the Liffey is regulated by the ESB and levels were very closely monitored both upstream and downstream of Leixlip Dam during events on 29/11/09.
The Liffey Catchment Flood Risk Assessment and Management Study (CFRAMS) has commenced and the steering has met on two occasions to date. The Srteering group consist of officials from OPW, SDCC, FCC, DCC, KCC, WCC and ESB. The CFRAM Study will cover the Liffey catchment as opposed to the main channel and therefore will deal with the Griffeen, Poddle and Camac Rivers also.
The ESB has also carried out some flood risk analysis on the Liffey main channel.
It is worth noting that some significant works have been done on Griffeen, Poddle and Camac aleady.
Griffeen
Major works were carried out on the Griffeen Catchment after the major floods of 2000. The Griffeen from the Kildare Rail Line to the Liffey is predominately through parkland and some attenuation has been provided adjacent to the new Adamstown Road, whilst south of the rail line, a significant portion of the river flows through an improved channel system at Grangecastle. Whilst this is zoned industrial, the river has been afforded maximum protection and significant improvement works have been completed including provision of an upgraded culvert under the rail line itself.
Tobermaclugg
The Tobermaclugg Stream Improvement works associated with the Adamstown SDZ are near completion. These work will divert surfacewater from the Adamstown Scheme directly to the Liffey. Some localized flooding still occurs on Tubber lane and this is currently being addressed.
Poddle
Improvement works have been carried out on the Poddle with attenuation being provided at Tymon and there are plan to install a new hydrometric station downstream of Tymon Ponds to further monitor this stream. The stream has historically impacted on the residential areas of Whitehall Road and improvements have been carried out on the surfacewater system in this area. There are a number of screen on the Poddle and these are routinely maintained.
Camac
Major attenuation and flood alleviation works have been carried out on the Camac from the M7 to Clondalkin through Corkaigh Park and Clondalkin The River through Clondalkin village itself has not flooded since these works were completed however routine maintenance is required. Once the Camac crosses the M50 it enters major industrial lands and is culverted. This Culvert is problematic. Two tributaries of the Camac, namely the Robinhood Stream and Ballymount Stream flow generally through industrial land and have historically caused problems. This situation is monitored closely however improvements are required on these streams.
The zoning map shows the the Camac and other tributaries flowing through the industrial zoned land of Citywest – these streams appear well catered for at Citywest. Citywest Ltd have provided significant attenuation on their lands.
A number of water holding features on the Camac, associated with historical mills, such as the Brittas Ponds and the Clondalkin Mill Pond may need to be assessed.
Dodder
The Dodder CFRAM Study is nearing completion and flood mapping and modeling has been carried out. It is intended early in 2010 to have Public Information days where the reports and maps produced to date will be made available to the public.
The Dodder through the County is well catered for in terms of available lands and green belts. The River is somewhat controlled by way of Dublin City Council 2 reservoirs in the upper catchment. The Dodder has experienced significant rises in water levels in recent years however the actual river itself has not caused damage to property on those occasions. The urban area for the Dodder Main Channel is in Templeogue and this has been fully assess in the CFRAM reports.
The tributaries of the Dodder have also been assessed in the Dodder CFRAM Report.
The Tallaght Stream flows through the park area of Jobstown and the industrial area of Whitestown where routine maintenance is required on an ongoing basis. Sean Walsh Park provides a green belt for the stream before it enters the Dodder itself through some residential areas adjacent to the N81.
The Whitechurch Stream has a flood study completed under the Dodder CFRAM study as a result of serious flooding in 2007. The most significant risk was found to be at Whitechurch School and this has since been addressed.
The Owendoher is also covered under the Dodder CFRAM report and flood risk maps will be publicly available during the upcoming Public Information days.
Both the Whitechurch Stream and Owendoher flow through residential property north of the M50, however south of the M50 both streams are in relatively rural areas.
The Ballycullen Stream in now only visible beyond Woodtown having been substantially piped through Ballycullen and Firhouse. This surfacewater system requires monitoring and can at times beach the pipework.
The above is a brief summary of the main rivers and streams in South Dublin. In general, the rivers and stream have satisfactory space to flow or sufficient attenuation is in place to control flows. These river and streams all flow close to residential, commercial or industrial properties. Notwithstanding the amount of works that has been done over the last 10 years in South Dublin regarding flood alleviation, the implementation of river and stream buffers zones, attenuation of surfacewater in all significant development, and routine maintenance screens on the rivers and stream, flooding can still occur. The variables of downpour intensity, existing ground saturation, location of downpour, riparian maintenance in private property, and sizes of existing culverts and bridges all play are role in where a flood will occur. South Dublin, through (a)implementation of the CFRAM Plans with flood mapping of all the rivers and streams (b) implementation of the Dublin Regional Drainage Code of Practice with regard to buffer distances from rivers and streams and installation of attenuation and SuDS and (c) implementation of the County Development Plan will continue to make improvements on the flood management of the County.