OCSC were appointed to conduct a Flood Impact Assessment for a new residential development located on zoned lands in north County Dublin. The site is situated adjacent to the River Sluice and is within the natural floodplain of the River Sluice. The study was carried out in order to satisfy the requirements of the 2009 Guidelines on The Planning System and Flood Risk Management.
The study included a hydrological assessment of the River Sluice catchment to determine design flows. Various methods were employed to determine the design flood flows including; analysis of historical hydrometric data, flow determination using the Institute of Hydrology (IH) method IH124, flow determination in accordance with the Flood Studies Report (FSR) and the Flood Studies Supplementary Reports (FSSR).
For the purposes of hydraulic design, a one-dimensional (1D) computational model of the River Sluice and its floodplain was constructed using the HEC-RAS river modelling package developed by the US Army Corps of Engineers. HEC-RAS is an industry standard for 1D hydraulic models.
To facilitate the development, ground raising was required to raise the Finished Floor Levels above the predicted design flood water level. The study also identified mitigation measure to compensate for the resulting loss of floodplain.
In consultation with planning consultants, OCSC prepared a report to address the requirements of the Justification Tests as set out in the 2009 Guidelines. The project received planning permission from Fingal County Council.