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 for droughts and floods analysis were conducted only from the perspective of a single factor (precipitation), while ignoring the impact of the underlying surface on the formation of droughts and floods. Based on the daily precipitation data of 88 meteorological stations in Hainan Island from 1970 to 2019, 30 m resolution DEM data and land use dataset, etc., the precipitation Z index was used to evaluate the level of drought and flood in Hainan Island. The analysis results were revised by underlying surface data to evaluate the spatiotemporal characteristics of the drought and flood areas. The drought- and flood-prone areas in Hainan Island were divided. The results show that the overall drought areas show an obvious downward trend, while the flood areas present an increasing trend. The drought-prone areas throughout the year are more concentrated in the northeast of Hainan Island, while the flood-prone areas are mainly distributed in the eastern coastal areas. The drought- and flood-prone 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 drought- and flood-prone areas before revision are 7.97 and 2.91 times larger than that after revision, respectively. Finally, combining climate and underlying surface factors, suggestions for drought and flood prevention are put forward.