PPS 15 Planning and Flood Risk (Revised)·Page 30·6.3
Flood Risk Comparison and Planning Policy
Explains that coastal flood plains have lower annual probability but greater risk to life from rapid inundation, so planning policy for both river and coastal flood plains is broadly similar.
While there is a lower annual probability of flooding within coastal flood plains compared with river flood plains, the effect of rapid inundation by fast flowing sea water presents a greater risk to life, hence planning policy for development in both cases is broadly similar.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/PPS 15 - Planning and Flood Risk (Revised).pdf