Cotabato City sits on low ground near the mouth of the Rio Grande de Mindanao, at the end of a very large river basin. For a buyer there, flooding is the first conversation. Here is what to screen.
Cotabato City sits on low, flat ground near the mouth of the Rio Grande de Mindanao, one of the largest river systems in the country. Everything about the hazard picture there follows from that position.
A big basin collects rain from a very wide area and moves it through a narrow set of channels near the coast. Two consequences for a buyer:
For any address here the lines to read together are mapped flood exposure, the distance to the nearest mapped waterway, and elevation. In flat country those three are one story, not three, which is the point of how to read a flood hazard map and elevation and slope.
Parts of this basin are naturally marsh. Marsh tells you two things: water sits here, and the ground underneath is soft.
The first is a flood-duration question. The second is a foundation question, and it belongs to a geotechnical investigation rather than a hazard map. A screening tells you whether that investigation is clearly worth the money on this lot. The line between the two is drawn in hazard map vs. geotechnical survey.
Near the coast, seawater pushed inland by a storm is a separate hazard from river flooding, with its own map. Read the storm surge line together with elevation for any address near the shore. See the storm surge brief.
Mindanao has mapped active faults, and a screening reports the distance from your address to the nearest mapped one. On soft, saturated ground, shaking behaves differently than on firm ground, and liquefaction becomes a question worth raising with your engineer. Our reports label liquefaction as an estimate, and the reason is explained in what is liquefaction.
Buyers ask how deep. In a large, flat basin the more useful question is how long.
Depth damages what the water touches. Duration damages everything else: the walls stay wet, mould takes hold, the road stays cut, the business stays closed, and the repair bill grows for every day the water refuses to leave. A shallow flood that sits for a week can cost more than a deeper one that drains in a day.
Mapped hazard data describes exposure, not duration, so this is a question for people rather than layers. Ask neighbours, ask the barangay, and ask them in a way that gets a real answer:
That last question is the one that separates a drainage problem you might fix from a basin-scale reality you cannot.
Ask where the drainage in the area discharges, whether any flood control or road raising is planned nearby, and how the existing structures are maintained. Ask the planning office whether the parcel sits in an area their land use plan already identifies as constrained.
These offices hold records that no national dataset does, and the full explanation of what to ask for is in what your barangay and city hall can tell you.
On flat ground near a river mouth, the position of the structure within the parcel is a real decision rather than a matter of taste. A pad raised half a meter, set on the higher part of the lot, with the utilities and electrical panel above the historical high-water mark, is a different building from the same design placed at grade in the lowest corner. Decide that before the plans are drawn, with an engineer, and while it is still free to change.
A hazard screening reads public national datasets at your coordinates and reports what the mapped layers say. In a large basin it cannot tell you what is happening upstream today, how channels or embankments are being managed, or what the soil is like at depth. Use it to understand the standing exposure of a lot, then rely on local knowledge and a licensed professional for the rest.
CheckHazard does not replace a professional geotechnical or engineering survey.