Abstract:
Runoff and Rainfall are important factors in everyday life such as in agricultural cultivation and in the industries. Therefore, runoff and rainfall records in the past using statistical methods to forecast the future is essential for planning, dividing and imposing a policy to prevent flash floods in the eastern coast gulf river basin. As a result, the objective of this study is to analyze the effects of runoff and rainfall on flash floods, and to forecast rainfall in two years. The data used in this research is monthly runoff and rainfall taken from the Royal Irrigation Department and the Department of Meteorology. The researcher divided the data into two sets, namely analysis of hydrogeology from 2004-2013 and analysis of statistical data from 2000-2015. The results were concluded as follows. The effect of runoff on flash floods manifests itself most in Chonburi, whereas flash floods in Rayong, Chanthaburi and Trat were less affected by the effect of runoff in decreasing order. The forecast of factors that affect rainfall was conducted using multiple regressions to find a correlation between the independent variables and the dependent variables. The analysis of 144 months in the past to show wind speeds is the the factor that most affects rainfall, whereas dry bulb temperature and relative humidity are second-most and third-most affecting factors, respectively. Furthermore, time series analysis in this research is based on multiple regression with qualitative data of independent variables, whereby 1 year is divided into 12 seasons (1 season=1 month) to create variables of 11 factors. It is a binray variable, which is either 0 or 1. After that, The equation created by this method has a coefficient of determination of 0.811084. The data was used to forecast rainfall in January 2000-December 2015 (192 months). The forecased values of monthly rainfall between 2016 and 2017 decrease from the past.