Temporal and Spatial Distribution Characteristics of Drought and Flood Considering the Influence of Underlying Surface in Hainan Island, Tropical Areas of China

Most studies of temporal and spatial distribution characteristics of droughts and floods analysis were conducted only from the perspective of a single factor (precipitation), while ignoring the impact of the characteristics of the underlying surface on the formation of droughts and floods. Using the daily precipitation data of 88 meteorological stations in Hainan province from 1970 to 2019, the 30m resolution DEM data, land use dataset, etc, the precipitation Z index is used to evaluate the drought and flood levels in Hainan province. The analysis results were revised by underlying surface data to evaluate the spatiotemporal characteristics of the drought and flood area in Hainan province. The drought-prone areas and flood prone areas in Hainan province were divided, and on this basis, the set pair analysis method was used to identify the regions with alternating drought and flood areas in Hainan. The results show that the overall arid area shows an obvious downward trend, while the flood area presents an increasing trend. The drought-prone areas throughout the year are more concentrated in the northeast of Hainan Province, while flood prone areas are mainly distributed in the eastern coastal areas. The regions where drought and flood occur alternately are small but concentrated. The drought and flood prone areas and alternate drought and flood areas before and after the revision by the underlying surface were compared. It can be seen that the overall trend is relatively similar and obvious before and after the revision. The result of drought areas before revision is 20.43 times larger than that after revision. The flood prone areas before revision are 8.50 times larger than that after revision. The alternating drought and flood areas before underlying surface revision in spring and summer are 17.50 times larger than that after revision. Similarly, it is 48.64 times in summer and autumn, and 17.62 times in autumn and winter. Finally, combining climate and underlying surface factors, suggestions are put forward for drought and flood prevention.