N7 Naas Road Interchange
Client: Kildare County Council
Project Value: €6 Million
Services Provided: Environmental Impact Assessment of Surface Water Run-off from the proposed Road
Construct Hydraulic Model to determine Flood Alleviation proposals
Environmental Assessment of Flood Alleviation proposals and Cost Estimates.
Key Features:
KCC proposed to make improvements to the N7 National Primary Route (Naas Road). The section of roadway, straddles several
river systems. These rivers drain northwestwards under the N7 and combine, before reaching the River Liffey near Straffan.
J. B. Barry & Partners were commissioned by KCC to assess the impact of surface water drainage from the proposed road scheme
on the downstream reaches. This was investigated both in terms of increased flow and water quality. A baseline water quality
assessment of the rivers was carried out by J. B. Barry & Partners in conjunction with Bord na Mona. Mitigation measures and remedial works were
identified. During the EIS study it became apparent that there was a significant flooding problem in the downstream reaches.
This was mainly due to the magnitude of flow generated in the rural catchment compared to the actual capacity of the river
channels and structures. A low cost remedial measures report was prepared to identify immediate flood relief proposals.
A hydraulic model (MIKE11) of the catchment was constructed and flood alleviation proposals were determined and costed.
Options include flood storage ponds, larger culverts, flood embankments and cleaning out of the river channel and structures.
The model was calibrated against information and photos supplied by local residents and aerial photography of the November
2000 flood event as well as data from 7 water level recorders installed during the flood study.
Partial funding for the construction of the scheme was obtained in May 2002 and new culverts with some embankments were
installed during the Summer of 2002. Cost of interim works approx. €0.6m.