## 4 Discussion
### Hot Areas of Flood Disaster Research  
The Spearman correlation coefficient between the occurrence frequency and research frequency for flood disasters was only 0.679 at a 5% confidence level, indicating a positive correlation between the two but a weak one. High-frequency flood disasters and high-frequency research are concentrated in North America, Asia, and Oceania, while South America and Africa are low-frequency research areas. In terms of flood disaster occurrence frequency, the top 10 H-H type countries are China, India, Indonesia, the United States, the Philippines, Brazil, Pakistan, Bangladesh, Vietnam, and Iran. The top 10 H-L countries are Afghanistan, Colombia, Sri Lanka, Peru, Argentina, Haiti, Kenya, Ethiopia, Algeria, and Bolivia. The L-H type countries are Germany, Belgium, Austria, Poland, the Czech Republic, Portugal, Egypt, Jamaica, Switzerland, and the Netherlands. The top L-L types are Ghana, Mali, Cuba, Rwanda, Saudi Arabia, Burkina Faso, Nicaragua, Senegal, Zambia, and Benin.  
There is an obvious geographical imbalance in flood disaster research. In global terms, high-frequency research is concentrated in East Asia, Oceania, Western Europe, North America, and Brazil. The regions with low frequency research are distributed in Latin America and the Caribbean, Africa, Eastern Europe, West Asia, Central Asia, and Southeast Asia. Although research in these areas is relatively \"weak,\" most of them are greatly affected by disasters. For example, on 12 January 2010, a strong earthquake of magnitude 7.3 occurred in Haiti in Latin America and the Caribbean region, which caused at least 223,000 deaths and affected nearly 1.5 million people [29,30]. On 14 July 2021, another 7.2 magnitude earthquake occurred in Haiti, which killed at least 2207 people and affected nearly 600,000 [31]. In Asia, the Orissa cyclone that occurred in eastern India in 1999 killed approximately 10,000 people in the coastal area of the Bay of Bengal [32], and Tropical Cyclone Amphan, which landed off the coast of West Bengal, India, on 20 May 2020, caused 102 deaths in India and Bangladesh and affected more than 13 million people [33]. In East Africa, the short and long rainy seasons in Kenya over the past two years were shorter than those in previous years. The consequent drought has caused severe water and food shortages, affecting approximately 2.1 million people [34].  
In intercontinental terms, Figure 4 shows that the disaster occurrence and research in North America and Oceania are of the H-H type. South America is characterized by polarization. Brazil has attracted high-frequency disaster studies, but only a few studies have been conducted in other countries in the region. Asia is a mixture of four types withdiverse distributions. Europe displays a gradient change in research frequency from high to low, from western Europe to middle and eastern Europe. Africa displays low frequency occurrence and low frequency research, but there are also internal differences among East Africa, Central Africa, and West Africa, which are distributed along a strip. Based on the above analysis, it is suggested to focus on regions with high-frequency disasters but low-frequency studies, such as Latin America and the Caribbean, Africa, Eastern Europe, and West Asia. These regions should increase investment in disaster prevention and reduction and pay more attention to policies.