Flood Warning by An Antecedent Precipitation Index for Chanod Basin

Abstract

Chanod Basin is located in Dong Luang District, Mukdahan province and That Phanom District, Nakhon Phanom province. There is Chanod Creek as the mainstream which has a relatively high slope at upstream and a lower slope before flowing into the Mekong river, Wan Yai District, Mukdahan. The nature of the flooding in Chanod basin is therefore characterized by the flash flooding in the upstream area, occurred in a short period of time. Baan Dan Sawan area, Um Mao Subdistrict, That Phanom District, Nakhon Phanom and nearby areas are one of the important economic villages located in Chanod Basin, which has been frequently affected by floods. From the floods in the past was found that the damage in that area was high due to the inability to warn and evacuate in time. The objective of this study was to find a way to prevent flooding from entering into Baan Dan Sawan by using the Antecedent Precipitation Index (API), which is an index used to measure the amount of soil moisture accumulated, a result of the Rainfall accumulation. The higher the Rainfall Index (API), the higher the chance of flooding. In this study, the daily accumulated rain was calculated and converted into the precipitation index. The daily rainfall data used in this study was based one rain gauge station, named 240220 during the years 1998 to 2018, to calculate for the flood warning by using Baan Kon Sawan Kh.91 station as a forecasting station. It was found that when the amount of rainfall in Chanod Basin above Baan Khon Sawan station, Kh.91, rained more than 150 mm. for 3 consecutive days and the Rainfall Index (API) was equal to 150 mm. will cause flooding in the area of Baan Dan Sawan, Um Mao Subdistrict, That Phanom District, Nakhon Phanom. The results of this study can be used to warn of flooding in the area of Baan Dan Sawan.