Flooding

What are the properties of lands susceptible to flooding? Maybe specifically a small island? How might I map this kind of area? I appreciate any kind of info that's related to this subject.

For starters, they are close to sea-level, near a body of water, and they are usually have very dense ground that water can't be absorbed through. If it's a small island, then they primarily deal with storms. Also, any basin-like area near mountains or cliffs makes it like a really big swimming pool. If there are villages there, then they usually have signs saying "Do not build anything beyond this point" because floods could wash it away. Buildings are on posts, and if they're REALLY used to it they have canoes or something nearby so they can float. Beaches might be bare because the sand was used to reinforce walls, any marinas have jetties or rock walls to reduce waves, and people try to build something squat and sturdy with multiple exits.

Also lets say the water breachs stop working and it rains really hard
there you go
a flood

Lit thanks! I'll incorporate that