WATER OVERFLOW OF THE RIVER ANALYSIS BASED ON THE COMPUTER PROGRAM SIMULATIONS (CPS)

The purpose of this study is to the analysis of water overflow during wet seasons in Indonesia especially in Palembang district which frequently involved in annual monsoon floods and the question of whether the wells can be used during floods as well as an alternative source when there are no floods. Rainfall intensity is calculated by the first time to calculating the time of concentration and the calculation of the time of concentration using the Kirpich formula. Rainfall intensity has a relationship between the length of rain that lasts and the frequency of rain which is usually called the IDF (Intensity Duration Frequency) curve. From this curve, it can be seen the amount of rainfall intensity with a return period of 2, 5, and 10 years. The result of the research design discharges used for each return period is Q2 of 58.176 m3 /sec, Q5 of 68.990 m3 /sec, and Q10 of 76.150 m3 /sec. Based on the simulation results using the HEC-RAS 4.1.0 program there was overflowing of the river at stations 800, 900, 1000, 1100, 1200, 1300 and 1450 with a return period of 2 years and the station of 100, 200, 300, 400, 500, 600 and 700 there was no overflow or still safe. In the return period of 5 and 10 years there was overflow at stations 100, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, and 1450. While at stations 200 and 300 there was no overflow