The design of the scheme brought together several specialist engineering disciplines within Roughan & O’Donovan to ensure that the highest ecological and environmental standards were achieved.
John Paul Rooney

John Paul Rooney



Roughan & O’Donovan brought this flood defence scheme from feasibility and conceptual design, through planning and detailed design, to construction.  

We also undertook the role of PSDP for the scheme.


Roughan & O’Donovan was commissioned by Dún Laoghaire-Rathdown County Council (DLRCC) and Transport Infrastructure Ireland (TII) to examine the cause of severe flooding on the M11 motorway in 2013 and undertake an assessment of the wider catchment of the Crinken Stream.

We used the Infoworks RS modelling package to undertake a detailed hydrologic and hydraulic analysis of the catchment.

Flood defence measures incorporated into the design included:

  • 1.6km of flood relief culvert along Old Connaught Road
  • An upgrade of 2km of longitudinal motorway drainage
  • New culverts
  • Channel widening with flood bunds


The works took place in a highly urbanised environment with heavily trafficked roads and, as such, required significant traffic management measures.

Extensive consultation with affected landowners proved necessary as the flood alleviation measures involved works on private property.

Services provided:

  • Hydraulic assessment and modelling
  • Feasibility and conceptual design
  • Options study
  • Preliminary and detailed design
  • Statutory and legal services
  • Environmental assessment
  • Contract documents
  • Construction supervision
  • Project management
  • PSDP