A hazard report can tell you your lot sits several metres above sea level and outside every mapped flood polygon. Then it rains hard for two hours and the street is knee deep.

Both things are true. Elevation describes the ground. Drainage describes what happens to water once it is on the ground, and drainage is built, maintained, and blocked by people. No national dataset knows the state of your street's canal.

This post is about checking the part the map cannot see.

Elevation and drainage are different questions

Elevation is how high your point sits. It is measured from terrain data and it is stable. It tells you whether rising water can reach you.

Drainage is whether water that lands on or near your lot has somewhere to go, and how fast. It depends on pipe sizes, canal depth, silt, garbage, the level of the road, whether the outlet is open, and whether the receiving channel is already full.

You can be high and badly drained. That is the classic urban case: water does not come up to you, it falls on you and cannot leave.

The elevation and slope brief explains what the terrain layer measures. Everything below is what it does not.

Six things to look at on site

1. Find the outlet. Walk the street and find where water is supposed to leave. A canal, an inlet grate, a culvert under the road, a creek at the end. If you cannot find it, that is your answer.
2. Look inside the canal. Is it holding standing water on a dry day? Standing water in a drain on a sunny afternoon means it is not draining. It is a container, not a channel.
3. Compare road level to lot level. If the road has been repaved several times, it may now sit higher than the properties beside it. A road that is higher than your gate is a dam.
4. Check the gradient. Water needs a fall. Pour a bottle of water on the road in front of the lot and watch which way it goes, and how quickly. It is a crude test and it works.
5. Look for silt lines and debris. A line of dried mud along a wall or fence at a consistent height is a record of where water sat.
6. Find out who maintains it. Barangay, city engineering office, subdivision association, or nobody. "Nobody" is a common and expensive answer.

Three questions for the neighbours

• After a heavy afternoon rain, how long before the street clears?
• Has the road been raised since you moved in?
• Who cleans the canal, and when did they last do it?

The third question gets the most useful answer, because people who live with a bad drain know its maintenance history in detail.

Signs a subdivision has a drainage problem

• Every house has a step up at the gate, and the newer houses have taller steps.
• Sandbags stored where they are easy to reach.
• Perimeter walls with weep holes that have been sealed shut.
• A pump in the guardhouse.
• Cars parked on a raised area during the rainy months.

None of these appear in a listing photo, and all of them are visible on a viewing if you are looking for them. The related check for gated developments is in a flood control project near you is not a guarantee.

How this changes what you do with a good report

A clean flood screening is genuinely good news. It means rising water is unlikely to reach you. Pair it with a drainage inspection and you have covered both halves of the problem:

• Map covers: will water rise to this point.
• Site visit covers: can water leave this point.

Buyers who only do the first end up surprised. Buyers who only do the second miss the river.

Checklist

1. Screen the coordinates for flood susceptibility, elevation, and waterway distance.
2. Walk the street and find the drainage outlet.
3. Look into the canal on a dry day and check for standing water and silt.
4. Compare road level to lot level and to the neighbours' gates.
5. Ask three neighbours how long the street takes to clear after heavy rain.
6. Find out who maintains the drainage and when it was last cleaned.
7. Visit in rain and watch it happen.

The honest limit

A hazard screening reports mapped susceptibility, elevation, slope, and distances from public national datasets. It has no visibility into a specific canal, culvert, or pumping arrangement, and it cannot know that the road was raised last year. Drainage is a local, physical, human-maintained system, and checking it is a job for your own eyes and the municipal engineering office.

CheckHazard does not replace a professional geotechnical or engineering survey.