Complex sentence: This suggests that coastal flooding from storm surges will become more frequent with sea level rise (Dawson et al.2009) and a rise in sea level alone threatens increased levels of flooding and permanent inundation of low lying land (Nicholls 2002, Michael 2007).
Split into simpler sentences: This suggests that coastal flooding from storm surges will become more frequent with sea level rise (Dawson et al.2009). A rise in sea level alone threatens increased levels of flooding and permanent inundation of low lying land (Nicholls 2002, Michael 2007).