When buying a house or a condo, most people prioritize the location—proximity to the skytrain, workplace, price per square meter, or room design. However, there is one factor that many overlook, despite its direct impact on residential safety and long-term property value: "flood risk."
Especially in the Bangkok metropolitan area, where the terrain is relatively flat, drainage systems have limitations, and weather conditions are becoming more volatile every year, checking for flood risk before deciding to purchase is not an overreaction but "homework" that should be done alongside reviewing the sales contract.
This article will walk you through 3 practical ways to check flood risk yourself, without needing an expert.
1. Check Flood Hazard Maps
Currently, there are online tools that provide area-specific flood risk information, most of which are accessible to the public for free.
Recommended sources to check:
GISTDA Geo-Informatics and Space Technology Development Agency: Provides data on repetitive flood-prone areas from satellite imagery over many years, helping you visualize how frequently a location has flooded.
Department of Disaster Prevention and Mitigation (DDPM): Often provides data on hazard-prone areas and provincial disaster alerts.
Longdo Map Flood Data Layer: Some versions overlay historical flood data onto the map, allowing for clear location identification.
Comprehensive City Plan (Bangkok or relevant province): Specifies low-lying zones or floodways, which carry legal weight.
Basic usage:
Search for the property name or coordinates (street, alley, district) in these systems and see what risk zone the area falls into. Some systems use color codes, such as green (low risk), yellow (medium risk), and red (high risk).
Precaution: These maps are based on historical data and models; they do not guarantee that flooding will not occur in the future, especially if new construction in nearby areas redirects water flow.
2. Investigate Local Flood History
Map data may not be detailed enough. Investigating the actual flood history of the area is another step to confirm the risk more accurately.
Sources and search methods:
Search archived news: Search for the street, alley, or village/project name along with the word "flood" for past years. Local news and social media often have images and reports from actual sites.
Ask local district/municipality offices: Local authorities usually have records of recurring flood spots in their jurisdiction, and some mark the highest flood levels on utility poles or public buildings.
Ask neighbors or locals: This is the most direct and current method. Ask people who have lived in the alley for a long time if they have ever experienced flooding, how often it happens, how high the water gets, and how long it takes to recede.
Ask the juristic person/project manager: For condos or housing estates, the juristic person usually keeps logs of past flood events, including the countermeasures the project has used.
Essential questions to ask:
How many times has it flooded in the past 5-10 years?
What was the cause of the flooding (heavy rain, high tide, overflowing river, drainage failure)?
How long did it take for the water to recede?
How high did the water reach (street level only, or inside the house)?
3. Measure Elevation Relative to the Road Yourself
Even if the overall area has a medium risk, individual houses or condo units may have different elevations, which directly affects the chance of actual flooding.
Things to observe during a site visit:
Floor level vs. road level: A good house should be raised at least 30-50 centimeters above road level to significantly reduce risk. Observe this with the naked eye or use a spirit level.
Alley road level vs. main road: Some alleys are lower than the main road, making it easy for water from the main road to flow into the alley during heavy rain.
Project location relative to surroundings: If the project is situated in a basin or lower than the surrounding area, water from nearby will pool there first.
Water stains: Look at fences, utility poles, or neighboring walls for horizontal water marks, which indicate past flood levels.
Alley drainage system: Check if there are drains or nearby canals. See if the pipes are clean or clogged with trash.
For condos, check additionally:
The location of electrical and pump rooms; if they are in the basement or on the ground floor, they are the first to be affected by flooding.
The floor level of the G-floor or Lobby relative to the road in front of the project.
Whether the parking lot is underground and if there are flood prevention systems.
Summary: Pre-purchase Checklist
Before signing the sales agreement, use this short checklist to review:
Check the flood hazard map from government agencies or mapping apps with flood data layers.
Search for past news and consult local authorities about flood history.
Ask neighbors or long-time residents in the area.
Visit the site and observe the floor level compared to the road.
For condos, check the location of electrical rooms and parking lots.
Checking for flood risk might take a little extra time before making a purchase, but compared to the potential damage to your property and the long-term repair costs, it is definitely worth it.
