On December 30, 2014, a sudden flood occurred in Chiva, Valencia, Spain, with a 24-hour rainfall of 114.8 mm. The slow local disaster relief led to public outcry. An in-depth analysis of the causes of the extreme rainstorms in Spain this year and the corresponding solutions:
Climate factors:
1. Extreme weather system: The disaster was mainly caused by the “Dana” extreme weather system. When the cold air moves over the warm Mediterranean waters, the hot air rises rapidly to form dense rain clouds. These rain clouds can stay in the same area for several hours, bringing a lot of rainfall.
2. Climate change: Global warming has significantly increased the temperature of the Mediterranean sea water, intensified the evaporation of water vapor, made the water vapor transport and convergence more intense, and may increase the intensity of extreme precipitation. At the same time, the increase in temperature allows the atmosphere to accommodate more water vapor, resulting in frequent extreme weather events such as rainstorms. In addition, the extreme drought and extreme high temperature that Spain has experienced before have reduced the surface vegetation coverage, reduced the ability to absorb and store rainwater, and also exacerbated the rapid formation of floods.
3. Topographic factors: There are many mountains in Spain, and the existence of mountains affects the runoff direction and speed of rainfall. When a large amount of rainfall occurs in the mountains, the rainwater will quickly gather to form surface runoff, and converge along the hillside to the valleys and rivers. In some low-lying areas, such as coastal plains, floods are difficult to drain naturally and can easily accumulate to form floods. In addition, the soil in some parts of Spain is loose and soil erosion is serious. When encountering short-term heavy rains, the soil cannot effectively absorb and fix water, and the rainwater will quickly form torrents, further exacerbating the harm of floods3.
4. Human factors: The urbanization process is accelerating: A large amount of natural land has been developed for the construction of houses, roads and industrial facilities, etc. The proportion of impermeable ground in cities has increased significantly, making it impossible for rainfall to penetrate into the ground, but quickly forming surface runoff, which not only increases the risk of urban waterlogging, but also increases the drainage pressure of rivers3.
5. Lagging flood prevention awareness: Because most parts of Spain have been facing drought and semi-drought problems for a long time, governments at all levels have attached great importance to drought and desertification resistance, and flood prevention awareness is relatively lagging behind. In some river basins, the construction and maintenance of flood control facilities may not have received enough attention, resulting in the inability to effectively resist floods when facing extreme rainfall weather.
Solutions
1. Strengthen meteorological monitoring and early warning: Optimize the monitoring network: Increase the number and distribution density of meteorological monitoring stations, especially in areas susceptible to extreme rainstorms, such as coastal areas and mountainous areas, to obtain more accurate and comprehensive meteorological data.
2. Improve forecasting technology: Use advanced meteorological forecasting models and technologies, combined with satellites, radars and other observation methods to improve the forecast accuracy and timeliness of extreme rainstorms, and timely release accurate rainstorm warning information.
3. Establish an early warning linkage mechanism: Strengthen communication and cooperation between meteorological departments and governments, communities, media, etc., establish fast and effective warning information release and dissemination channels, and ensure that warning information can reach every resident in a timely manner.
4. Improve flood control infrastructure construction: Build and strengthen dams: Build high-standard dams and flood control walls in rivers, coastal areas and other places susceptible to floods, and conduct regular inspections and reinforcements to improve their flood control capabilities.
5. Optimize drainage systems: conduct a comprehensive assessment and transformation of urban and rural drainage systems, increase the diameter of drainage pipes, add rainwater pumping stations and other facilities, and improve the drainage capacity of drainage systems. At the same time, promote green infrastructure such as permeable pavement and rainwater gardens in cities to increase the natural infiltration and storage capacity of rainwater.
Build flood storage areas and reservoirs: Build flood storage areas and reservoirs in appropriate locations, store excess flood water during heavy rains through scientific scheduling and management, and reduce flood control pressure in downstream areas.
6. Optimize urban planning and land management: Rationally plan urban layout: In urban planning, avoid large-scale construction in low-lying areas that are susceptible to floods, and layout important functional areas and residential areas of the city in places with higher terrain and less susceptible to floods.
7. Increase urban green space and permeable area: Increase urban green space rate, build urban green spaces such as parks, squares, and wetlands, and promote the application of permeable materials such as permeable concrete and permeable bricks to increase the permeable area of the city and reduce surface runoff.
Protect and restore natural ecosystems: Strengthen the protection and restoration of natural ecosystems such as rivers, lakes, and forests, maintain their ecological functions, such as water conservation and flood regulation, and reduce the risk of floods.
8. Improve public awareness of flood prevention and emergency response capabilities: Carry out publicity and education activities: Through television, radio, the Internet and other media, as well as schools, communities and other channels, widely carry out publicity and education activities on flood prevention knowledge to improve the public’s awareness and awareness of extreme rainstorms and floods.
9. Organize emergency drills: The government and the community should regularly organize flood prevention emergency drills to familiarize the public with the response measures and escape methods when floods come, and improve the public’s emergency response capabilities and self-rescue and mutual rescue capabilities.
10. Reserve emergency supplies: Communities and families should reserve necessary flood prevention emergency supplies, such as food, drinking water, life jackets, flashlights, etc., to cope with possible flood disasters.
Strengthen regional cooperation and international assistance:
1.Domestic regional cooperation: Strengthen cooperation and exchanges between different regions in Spain in flood prevention and disaster reduction, share experience and technology, and be able to promptly deploy human, material and financial resources for support and rescue when disasters occur.
2.International cooperation and assistance: Actively cooperate with international organizations and other countries, introduce advanced flood prevention technology and management experience, strive for assistance from the international community in terms of funds, materials, etc., and jointly respond to the challenges of extreme rainstorms and floods brought about by climate change.
