Evaluating Variation in the SCS Runoff Curve Number 2 (CN2) Efficiency during Flash Flood and Land Use Change Situations using SWAT Model in Loei Basin

Abstract

The flash flood was common problem in immerse flood season. It destroyed shelters and agricultural plain area. The causes were heavy rain from river source to river mouth and changing of land used. The purposes of this study were 1.) To apply “SWAT” model to evaluate the effective of water flowing at Loei basin, Loei province. (Khong river of Northeastern river region, Thailand) 2.) To compare water quality of flash flood occurred in year 2002, 2011 and 2017 with year 2009 effected with land used. The results were as conditional water level in daily from “SWAT” modal compared with measurement station was at KH.58A in year 2009. The reliability was at R2 NES and PBIAS was at concessive level. The changing of soil used tendency compared with three periods of time that amplified to country side, sugar cane gardens and also rubber gardens. Especially in rubber gardens, price was increased instead of old agriculture. The water of land surface level was increased in rainy season at 30 percentage and related with CN2 increased. The minor river was water collected point and agricultural area was changed to city. This study could apply to make data decision, set land used administration, set water resource for people and for government agencies that could face with hydrology flash changed in immerse flood season.