Reference
What the colours mean
A colour is only useful if you know what it costs you. Here is each hazard level in metres, in furniture, and in decisions.
Low
0.1 – 0.5 metresShallow flooding
Water reaches your ankles or knees. Streets become impassable to motorcycles and small cars. Anything stored on the floor gets wet.
What to do. Move belongings off the floor. Avoid driving through it — half a metre of moving water can float a small car.
Medium
0.5 – 1.5 metresModerate flooding
Water reaches your waist or chest. A single-storey house takes water throughout. Electrical outlets are submerged. Wading becomes dangerous once it moves.
What to do. Evacuate early, before the water reaches this depth. Cut power at the breaker if it is safe to do so.
High
Over 1.5 metresDeep flooding
Water goes over an adult's head. Single-storey homes are fully submerged. This depth is life-threatening regardless of how well you swim, because of current and debris.
What to do. Do not wait. Evacuate as soon as a storm is forecast — not when the water arrives.
A “100-year flood” is not a once-a-century flood
It means a 1-in-100 chance in any given year. Two can land in consecutive years without the model being wrong — the same way rolling two sixes in a row doesn't break the dice. And the risk compounds:
Chance of at least one 100-year flood, assuming independent years.
- 5-year20%/yr
- The flood you can expect roughly every few years. The most useful one for everyday planning.
- 25-year4%/yr
- A serious storm. Bigger footprint, deeper water, more barangays affected.
- 100-year1%/yr
- The worst case in the model. Use it to know where you would go, not where you'd stay.