Dagupan sits on the delta of the Pantal and connected rivers where they meet the Lingayen Gulf. It is low, flat, criss-crossed by tidal channels, and built on young sediment.

Every one of those words is a hazard input.

The ground is the headline

In the July 1990 Luzon earthquake, Dagupan suffered severe damage of a distinctive kind. Buildings did not pancake, they sank and tilted. That is liquefaction: loose, water-saturated sandy soil losing strength when shaken and briefly behaving like a liquid.

That is exactly the ground a river delta produces. See what liquefaction is, and why we label it an estimate, and the full account of that earthquake in July 1990.

Two things follow for a buyer here:

1. Read the liquefaction estimate on the screening, and treat it as a reason to invest in a soil investigation rather than as a verdict.
2. A geotechnical investigation is genuinely important, not a formality. On delta ground, what the foundation has to do is a real engineering question. The distinction is in hazard map vs geotechnical survey.

Flooding, from three directions

Dagupan has a well-earned reputation for flooding, and it comes from more than one source.

• River flooding from the Agno system and the local channels after heavy rain upstream.
• Rainfall flooding on flat ground with limited fall to the sea.
• Tidal influence, because the channels are tidal and a high tide reduces how fast anything drains.

Screen flood susceptibility, elevation, and the distance to the nearest mapped waterway together, and treat elevation as the critical number. On ground this flat, a few tens of centimetres is the entire margin. See the elevation and slope brief.

Also screen storm surge exposure, because the Lingayen Gulf is open water and the city is barely above it.

The provincial context is in buying in Pangasinan.

Subsidence, which is not on the report

Low delta cities with heavy groundwater use can subside, meaning the ground itself slowly drops. Where that happens, flooding gets worse over time even if rainfall does not change, and no hazard map records it because it is a process rather than a place.

Ask locally whether flooding has worsened over decades in ways that raising streets has not fixed, and ask the city engineering office directly. The general version is in why parts of Metro Manila are sinking.

Roads, fill, and the arms race

In flood-prone lowland cities, streets get raised, and then the houses beside them are below the road. Then those houses fill their yards, and their neighbours flood.

Check the level of the road against the lot, and against the neighbours on both sides. Ask when the road was last raised. This is the practical drainage question covered in your street is the problem.

Checklist before you commit

1. Screen the exact coordinates, not the barangay.
2. Read flood susceptibility, elevation, waterway distance, and storm surge together.
3. Note the liquefaction estimate and plan for a soil investigation.
4. Measure the lot level against the road and the neighbours.
5. Ask when the road was last raised and whether the lot has been filled.
6. Ask three neighbours for the highest water and the year, and how long it stayed.
7. Have any existing structure assessed by a licensed structural engineer, especially anything built before 1990.

The pre-1990 building question

Any structure that predates the 1990 earthquake in this city has either been through it or been repaired after it. Ask which, ask what was done, and pay a licensed structural engineer to look. On this ground, that is the highest-value item in the transaction.

The honest limit

A hazard screening reads public national datasets at a point and reports mapped susceptibility, elevation, and distances, plus a liquefaction estimate that is explicitly an estimate. It does not measure soil, track subsidence, or assess a building. Those need a licensed geotechnical engineer, the city engineering office, and a licensed structural engineer.

CheckHazard does not replace a professional geotechnical or engineering survey.