Hi Jane,
I worked on an AAP for a Local Authority in West Yorkshire a few years ago, which covered a city centre. The AAP had areas of Flood Zone 3. The evidence required to support making land use allocations was the same as any other Local Plan; undertake an SFRA level 1 and then level 2 if you want to meet the exceptions test of allocating land for development in Flood Zone 3. It may be that your Core Strategy / Local Plan has already undertaken an SFRA level 1 and level 2 assessment; therefore the evidence you need may already be available.
Undertaking a SFRA level 2 on a small area should not be too costly or time consuming.
If you want to give me a call, number is in my profile.
