Inundation
Overview
Inundation (침수, inundation/flooding) refers to the temporary or permanent submergence of land due to rainfall, storm surges, river flooding, rising groundwater, etc. Inundation causes particularly severe damage in urban areas, and its risk is increasing due to the rising frequency of heavy rainfall and sea-level rise driven by climate change. Inundation not only involves the simple submergence of land but also triggers secondary and tertiary damages such as traffic paralysis, power and communication outages, and the spread of waterborne diseases.
Main Content
Causes of Inundation
1. Meteorological Factors: The rainy season (장마), typhoons, and heavy rainfall (over 30mm per hour) are the main causes. The record of 141.5mm per hour in the Seoul-Gyeonggi area in 2022 is a typical example of localized heavy rainfall.
2. Topographical and Geological Factors: Low-lying areas, riversides, coastlines, and steep mountainous regions have high vulnerability to inundation. In particular, the increase in impervious surfaces (asphalt, concrete) due to urbanization prevents rainwater infiltration, sharply increasing surface runoff.
3. Infrastructure and Management Factors: Aging drainage systems, insufficient sewer capacity, inadequate river dredging, and drainage blockages caused by illegal structures exacerbate inundation.
4. Oceanic Factors: Sea-level rise, tsunamis, and storm surges during high tides cause coastal inundation.
Types of Inundation
- Pluvial Flooding (Urban Inundation): A phenomenon where rainfall exceeds drainage capacity, submerging roads and underground spaces. It is especially dangerous in semi-basement houses, subways, and underground shopping malls.
- Fluvial Flooding (River Overflow): A phenomenon where river water levels exceed levee heights or levees collapse, flooding surrounding areas.
- Coastal Inundation: Seawater overflow caused by typhoons or storm surges. Occurs in low-lying coastal cities (Busan, Incheon, etc.).
- Compound Inundation: The worst-case scenario where pluvial, fluvial, and coastal inundation occur simultaneously.
Cases of Inundation Damage
- 2022 Seoul-Gyeonggi Heavy Rainfall: Recorded 141.5mm per hour, resulting in 14 deaths; the loss of life due to flooding of semi-basement houses caused social shock.
- 2023 Chungcheong-North Jeolla Heavy Rainfall: Overflow of the Geumgang and Mangyeonggang rivers led to large-scale agricultural land inundation, with over 2,000 evacuees.
- 2024 Busan Coastal Inundation: Due to Typhoon Khanun, Haeundae and Gwangalli coastal roads were flooded, causing damage to shops and homes.
- International Cases: The 2021 Germany-Belarus floods (over 200 deaths), the 2023 Libya dam collapse (over 11,000 deaths), etc.
Inundation Preparedness and Response System
- Prevention: Maintenance of sewer pipes, expansion of rainwater pumping stations, installation of retention basins, reduction of impervious surfaces (permeable pavement, green spaces), reinforcement of river levees.
- Early Warning: Heavy rainfall advisories and warnings from the Korea Meteorological Administration, inundation forecasting and warning systems (based on river levels and rainfall), and disaster text message alerts.
- Response: Evacuation during inundation (to high ground or safe buildings), vehicle submersion escape techniques (unfasten seatbelt, break windows), shut off electricity and gas.
- Recovery: Disinfection of flooded areas (to prevent waterborne diseases), damage investigation and compensation, provision of disaster relief supplies.
Inundation and Climate Change
Climate change is a key factor exacerbating inundation risks. Global warming increases atmospheric water vapor, raising the intensity and frequency of heavy rainfall. Sea-level rise (annual average of 3.3mm) continuously increases coastal inundation risks. The IPCC Sixth Assessment Report projects a sea-level rise of 0.3 to 1.0 meters by the end of the 21st century, predicting a sharp increase in inundation vulnerability for low-lying coastal cities (Seoul, Busan, Incheon, New York, Shanghai, etc.).
Latest Trends
Key trends related to inundation as of 2024-2025 are as follows.
- Introduction of AI and IoT-based Inundation Prediction Systems: The Korea Environment Corporation and the Korea Meteorological Administration are piloting a system that predicts inundation risk areas one hour in advance using AI deep learning models. It combines IoT water level sensors and CCTV video analysis to monitor real-time inundation conditions.
- Expansion of Smart Drainage Systems: Seoul City plans to build 50 'smart rainwater pumping stations' by 2025, introducing remote control and automatic operation systems. Busan City is installing 'intelligent drainage gates' along the coast to block seawater inflow.
- Strengthened Measures for Semi-basement House Inundation: Following the 2022 disaster, the government mandated the installation of inundation alarms and flood barriers in semi-basement houses and is implementing a 'Comprehensive Safety Plan for Semi-basement Houses' that restricts new construction of such homes.
- Climate-Adaptive Urban Design: The 'Sponge City' concept is being introduced, expanding facilities for rainwater infiltration, retention, and reuse (green roofs, rain gardens, permeable pavement) within cities. From 2025, installation of inundation mitigation facilities will be mandatory for new residential land development.
- Strengthened International Cooperation: The UN Office for Disaster Risk Reduction (UNDRR) is pursuing a global initiative to build inundation risk assessment and early warning systems as a follow-up to the Sendai Framework. South Korea hosted the 'Asia-Pacific Inundation Risk Management Forum' in 2024.
Related Topics
- [[Flood]]
- [[Climate Change]]
- [[Urban Planning]]
- [[Disaster Management]]
- [[Sea Level Rise]]
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