Survey Overview
The National Institute for Land and Infrastructure Management conducted a large-scale questionnaire survey in January 2025 to understand home buyers' awareness of flood risk. The survey targeted 1,142 people aged 20 to 60 who purchased detached houses after 2015 in five cities: Kawasaki, Shizuoka, Okayama, Kurashiki, and Hiroshima. These cities were selected from municipalities with cumulative totals of 1,000 or more buildings experiencing above-floor flooding and total/partial destruction in flood statistics from 2014 to 2022, and populations of 300,000 or more in the 2020 census.
Approximately 30% of respondents had experienced some form of flood disaster, with roughly half experiencing disasters before purchasing their current homes and half after purchase. The analysis compared 186 people who experienced "home flooding" or "flooding in nearby familiar locations" before purchasing their current homes as the "experienced disaster" group, and the remaining 956 people as the "no disaster experience" group.
Flood Risk Recognition Status
Hazard Map Confirmation Rates
- Experienced disaster group: 85.5%
- No disaster experience group: 71.4%
While hazard map recognition has progressed relatively well regardless of disaster experience, the experienced disaster group showed a statistically significantly higher confirmation rate.
Past Flood Information Confirmation Rates
- Experienced disaster group: 67.7%
- No disaster experience group: 42.1%
Confirmation rates for past flood information were about 20-30 points lower than hazard map confirmation rates for both groups.
Comprehensive Flood Risk Confirmation Rates
The percentage who confirmed flood risk through at least one method among hazard maps, past flood information, or other methods:
- Experienced disaster group: 90.3%
- No disaster experience group: 76.2%
Among the no disaster experience group, when the previous residence was in the same postal code area as the current one, the percentage who did not confirm flood risk was significantly higher at 32.3%, indicating a tendency for decreased awareness of flood risk when relocating nearby.
Implementation Status of Flood Countermeasures
Flood Countermeasure Implementation Rates
Percentage who implemented any flood countermeasures:
- Experienced disaster group: 82.3%
- No disaster experience group: 49.0%
A significant difference in flood countermeasure implementation rates was observed based on disaster experience.
Specific Flood Countermeasure Content
Implementation rates for each countermeasure among respondents who took flood measures:
Selected areas with apparently low risk of flood damage considering elevation and surrounding infrastructure
- Approximately 45-47% implemented across all groups
Built structures resistant to flood damage
- Home flood experience: 45.2%
- Nearby flood experience: 24.1%
- No disaster experience: 18.8%
Confirmed evacuation routes from home
- Nearby flood experience: 52.9%
- No disaster experience: 52.1%
- Home flood experience: 37.0%
Reconfirmed flood insurance coverage
- Nearby flood experience: 46.0%
- Home flood experience: 35.6%
- No disaster experience: 27.8%
Priority Items in Residential Location Selection
Top 5 Items Commonly Prioritized
Both groups prioritized the following items:
- Price
- Spatial comfort such as lot size, sunlight, and ventilation
- Security
- Convenience for commuting and schooling
- Convenience for daily shopping
Differences Due to Disaster Experience
The experienced disaster group showed significantly higher priority levels in 11 out of 17 items compared to the no disaster experience group. Particularly notable differences were in:
- Difficulty of fire spread from surroundings
- Pedestrian safety
- Ease of evacuation during disasters
- Children's playgrounds and childcare support services
- Medical, welfare, and cultural facilities
- Distance from parents, children, and relatives
- Welfare and care life support services
- Relationships with neighbors and community
Regarding "susceptibility to flood and tsunami damage," while about 70% of the experienced disaster group prioritized it, no significant difference was observed between groups.
Disaster Experience and Relocation Patterns
Relocation destinations of the home flood experience group:
- Same postal code area as current: 47.7%
- Within same city (different postal code): 37.5%
81.8% of home flood experiencers had disasters after 2015, and even when relocating due to disasters, there was a confirmed tendency to acquire housing within a range that did not significantly change the environment from before the disaster.
Impact of Important Matter Explanations
Survey results from 508 people who purchased homes after 2020:
- Recognized risks beforehand, no impact: 43.7%
- First recognized risks through important matter explanation: 15.4%
- Received explanation but did not pay attention: 10.6%
- Do not remember if explanation was given: 23.8%
- Did not receive explanation: 6.5%
Impact from Real Estate Business Perspective
A survey of 884 member companies of the All Japan Real Estate Association (conducted November 2024) revealed:
Impact of Adding Flood Risk Information to Important Matter Explanations
- Reported impact: 28.2% (249 companies)
- Types of impact:
- Impact on demand and prices: 43.8%
- Customer interest and concern: 20.5%
- Real estate industry interest and concern: 5.2%
Specific examples included "More people are excluding areas designated as flood-prone zones on hazard maps from consideration" and "Corporate contracts are no longer being approved."
Real Estate Market in Disaster Areas
Responses from 307 companies with experience handling properties in flood disaster areas:
- Feel transactions are stagnating: 61.2%
- Feel transactions are occurring at lower prices/rents than usual: 51.1%
Survey Significance and Future Challenges
This survey revealed that disaster experience significantly affects flood risk recognition, flood countermeasure implementation rates, and considerations in residential location selection. While about 76% confirm flood risk even without disaster experience, actual flood countermeasure implementation remains at about 50%, revealing a gap between risk recognition and countermeasure implementation.
Additionally, disaster experiencers showed a strong tendency to value not only physical disaster prevention elements but also soft aspects such as life support services and community, suggesting that disaster experience has multifaceted impacts on residential location selection. Future challenges include surveying flood risk recognition and countermeasures among continuous residents.