A ramp leading down into a basement is, hydraulically speaking, an inlet. When the street floods above the level of the ramp entrance, water goes down it, and it keeps going down until the basement is full or the street clears.

In Metro Manila and other lowland cities, this is the single most reliably expensive loss in an ordinary flood.

What is in a basement besides cars

This is the part people underestimate. Basements also commonly hold:

• The main electrical room and the transformer.
• The domestic water pumps and the cistern.
• The sump pumps, which are supposed to deal with exactly this.
• Fire pumps.
• The lift pits and machinery.
• Generators.

Flooding those does not just cost money, it takes the building out of service. A tower with a flooded electrical room has no lifts, no water pressure, and no lighting in common areas, for as long as the replacement takes.

That is why a ground-level or basement flood in a condominium is a whole-building event, even for a unit on the 30th floor. See ground floor condo units.

Screen the ground the building sits on

At the exact coordinates of the building:

• Mapped flood susceptibility and elevation, which describe the street outside. See the elevation and slope brief.
• Distance to the nearest mapped waterway, including culverted creeks under city streets.
• Storm surge exposure for anything near a bay.
• The liquefaction estimate, on reclaimed or alluvial ground, which is a foundation and basement wall question.

The questions for the building administration

1. Has water ever entered the basement? When, how deep, and what was damaged?
2. Where is the electrical room, and is it above the basement floor level?
3. Where are the domestic and fire pumps?
4. Is there a flood barrier at the ramp, and has it been deployed? How long does deploying it take, and who does it?
5. What is the sump pump capacity, and what powers it when mains power fails?
6. Is there a procedure to move vehicles out, at what trigger, and has it ever been executed?
7. Where do vehicles go when the basement is evacuated?
8. Who is liable for vehicle damage, and what does the building's insurance cover?

Question six is the one that separates buildings that lose cars from buildings that do not. A written procedure with a named trigger and a rehearsed execution works. Announcing it over the PA when water is already at the ramp does not.

Question eight is worth pinning down in writing. Motor insurance and building insurance treat this differently, and "acts of nature" cover on a vehicle policy is often optional.

For the owner of the slot

• Find out the level of your specific slot. Basements slope, and the far corner is not the same as the ramp.
• Know the trigger and the destination for evacuation, and be reachable.
• Check your own motor policy covers flood, in writing.
• If you travel, leave keys with someone who can move the car.

Checklist

1. Screen the exact coordinates of the building.
2. Ask the administration all eight questions and ask for the flood procedure in writing.
3. Find out where the electrical room and pumps are.
4. Find out the level of your specific parking slot.
5. Confirm your motor insurance covers flood.
6. Agree who moves your car if you are away.
7. Walk the street outside and look for water lines on nearby buildings.

The honest limit

A hazard screening reports mapped susceptibility, elevation, and distances at a point. It knows nothing about a specific basement, its pumps, its barriers, or its management. Those come from the building administration, the association documents, and a licensed engineer if you want the structure assessed.

CheckHazard does not replace a professional geotechnical or engineering survey.