Complex sentence: The Office of Public Works (OPW) completed and installed a Flood Forecasting System which was used to forecast flooding in January 2008 and January 2009, the flooding of January 2009 being a 1 in 5 year event.
Split into simpler sentences: The Office of Public Works (OPW) completed and installed an Flood Forecasting System which has been used for the flood event of January 2008 and January 2009. The flooding of January 2009 being a 1 in 5 year event.