Driving Force Exploration for Flash Flood Based on Mann–Kendall Test and Geographical Detector: A Case Study of Hainan Island, China

Flash floods are among the deadliest hazards in China and have led to substantial casualties and losses, especially on Hainan Island. Therefore, it is of great significance to explore the main driving force behind them. Nevertheless, research on the driving force of flash floods is limited here. This study explores the driving force of flash floods on Hainan Island from 14 factors involving three categories: natural, social, and rainfall factors. Two quantitative methods, like the Mann–Kendall test and the geographical detector method, are applied. The Mann–Kendall test is usually used for time series trend analysis and is introduced to divide the flash flood periods into D95 (years from 1980 to 1995) and D14 (years from 1996 to 2014) through the results of reported flash flood trend analysis. The geographical detector is applied to analyze the driving force of flash floods. There are several key findings from this study that help better understand the driving force about flash floods. Firstly, the results show that the main driving forces of flash floods are natural factors like Elevation and Soil in both periods, and they are on the rise. Secondly, the influence of short-term heavy rainfall on flash floods is becoming more and more serious. Thirdly, even though the driving forces from social factors to flash floods are small, the impact of population density on that is significantly increasing.