【Geography General/Exploration】 Investigating Disaster Prevention and Living Spheres: The Power of "Maps" to Protect Our Lives
Hello everyone! In this chapter, we will learn about "what kinds of disasters are likely to occur" in the places where we live and "how to investigate them." While geography might have the image of being a memorization-heavy subject, this field is actually packed with "practical wisdom for protecting lives," making it an incredibly important section.
You might find the technical terms a bit daunting at first, but don't worry! We will take it one step at a time, keeping the familiar streets of your own neighborhood in mind. We will also master key concepts that frequently appear on the Common Test under "reading charts and diagrams."
1. The Relationship Between Japan's Natural Disasters and Topography
Japan is a disaster-prone country, even by global standards. The reasons for this lie in Japan's "topography" and "location."
① Mechanisms of Earthquakes and Tsunamis
The Japanese archipelago is located where four plates (massive slabs of rock) push against each other. As the plates move, strain builds up, and when it suddenly snaps, an earthquake occurs. Especially when a large earthquake occurs offshore, the seawater is pushed upward, causing a tsunami.
Key Point: Tsunamis travel faster in deeper water; as they approach the coast, their speed decreases, but in exchange, their "height" increases.
② Meteorological Disasters (Floods and Sediment Disasters)
Japan is characterized by steep mountains and short rivers. Because of this, heavy rain can easily lead to sudden flooding.
・Alluvial Fan: An area where sediment accumulates at the exit of a valley. While drainage is good, there is a risk of debris flows.
・Delta (Deltaic plain): Low-lying areas near a river mouth. Because the elevation is low, they are prone to damage from floods and storm surges.
【Pro Tip】
Old place names sometimes hide clues about the land. Locations with kanji characters for "snake" (hebi/ja), "water" (mizu), or "marsh" (numa) might have been areas prone to flooding in the past. It’s fun to check out the place names around you!
★ Summary of this section:
Because Japan is located at the boundary of tectonic plates and has steep topography, the risks of earthquakes, tsunamis, and floods are always present.
2. Concepts of Disaster Prevention: "Self-help, Mutual help, Public help" and "Disaster Mitigation"
To confront disasters, it is crucial to understand the three forms of cooperation. This is a concept frequently asked on exams.
・Self-help: Protecting yourself by your own means (stockpiling, securing furniture, etc.).
・Mutual help: Helping one another with neighbors (evacuation drills, checking safety, etc.).
・Public help: Rescue and support from the government or local authorities (dispatching the Self-Defense Forces, setting up evacuation shelters, etc.).
Also, in recent years, the idea has shifted not only toward "eliminating disasters entirely (disaster prevention)" but also toward "minimizing damage (disaster mitigation)." Since it is difficult to suppress the forces of nature 100%, the key is how effectively we can reduce the damage.
【Common Mistake】
It is dangerous to assume that "because there is a large levee, it is absolutely safe." Always operate on the premise that disasters exceeding expectations can occur, and make it a habit to check "hazard maps."
3. Investigating Living Spheres and GIS (Geographic Information Systems)
To understand the region where we live (our living sphere), modern geography utilizes high-tech tools. That tool is GIS (Geographic Information System).
① What is GIS?
Simply put, it is a "system that layers various information on top of a map." For example, you can overlay information like "elevation data," "past flood-prone areas," and "locations of evacuation shelters" like transparent sheets on top of a base map.
This allows you to see at a glance, "where is it dangerous, and where should I escape to?"
② Utilizing Hazard Maps
Hazard maps (disaster prediction maps) are created using GIS technology. These display danger zones for floods, sediment disasters, and tsunamis using color coding.
Key Point: Tips for reading hazard maps
1. Check which colored area your home is in.
2. Check the "route" to the evacuation shelter to see if there are any dangerous spots (bridges or steep slopes).
3. Think about whether "vertical evacuation" (escaping to the upper floors of a building) is possible if the area floods.
★ Summary of this section:
GIS is a tool for layering and analyzing information. Hazard maps are the ultimate weapon for knowing "where the danger is!"
4. How to Conduct Fieldwork (Outdoor Surveys)
Going out and researching on foot, rather than just looking at textbooks or maps, is called fieldwork. The Common Test may include questions about the procedures and manners of conducting surveys.
Step 1: Preparation (Preliminary Survey)
Don't just head out blindly. First, look at maps, statistical data, and old aerial photographs to form a hypothesis about "what you want to verify."
Step 2: Implementation (On-site Survey)
・Observation: Confirm things that maps can't show, such as differences in elevation or remnants of old buildings, with your own eyes.
・Interviews: Ask local people about things like past disasters. *Note: Respecting privacy and obtaining permission is a strict rule!*
Step 3: Conclusion
Summarize the results of the survey in maps or reports and verify whether your initial hypothesis was correct.
【Memorization Tip: The Fieldwork Set of 3】
"Walk (observe), Listen (interview), Summarize (analyze)." Keep this flow in mind!
5. Interpreting Statistical Data and Local Issues
To understand the situation of a region, numbers (statistical data) are indispensable. The following are commonly used:
・Population Census (National Census): Conducted every 5 years, this is the most fundamental survey to determine the reality of Japan's population and households.
・Land Use Map: A map showing whether land is "residential," "agricultural," or "commercial."
Examples of regional issues:
・Marginal Village (Genkai Shuraku): A village where more than half the population is over 65, making it difficult to maintain the community.
・Aging Infrastructure: The problem of many old bridges and roads becoming increasingly likely to collapse during a disaster.
By combining this data with hazard maps, specific issues become apparent, such as "an area with a high elderly population has very distant evacuation shelters."
★ Summary of this section:
Combining data (statistics) with the field (fieldwork) reveals the true state of a region.
Closing: Preparing for the Common Test
In this field of "Disaster Prevention and Investigation of Living Spheres," you will rarely encounter difficult mathematical formulas. Instead, you will be tested on your "ability to derive the correct answer by combining multiple provided maps and materials."
"If I were the disaster prevention manager for this town, what would I do?" Reading the problem from this perspective makes it much easier to solve. Good luck!