Analysis of Maximum Rainfall Trends in the Long Xuyen Quadrangle Area over Three Past Decades

Abstract

This study assesses heavy rainfall indices (HRIs) for the Long Xuyen Quadrangle (LXQ) of Vietnam based on daily rainfall data applying the Mann-Kendall test and Sen’s slope estimate, in order to detect the change trends in the period 1985-2015. The analyzed results show that approximately of 80 percent of study area was recorded a slight downward trend the number of heavy rainfall days above 20 mm. A significant downward tendency was also occurred at Ha Tien while Rach Gia station not record upward/downward trend and, a slight upward trend was observed at Chau Doc station. A tendency similar as the number of heavy rainfall days above 20 mm was also recorded for the number of very heavy rainfall days above 50 mm, a slightly upward trend was observed at five out of nine stations while a slightly downward trend was occurred at the three out of nine remaining stations and an absence of a clear trend at Xuan To station. A high concentration of the number of maximum rainfall days above 100 mm was recorded at Ha Tien station with approximately of 77 days/31 years (corresponding to 2.48 days/year), meaning that Ha Tien region is facing a higher risk of maximum rainfall event, leading to the inundation of planting crops.