Forecasting the air Bengkulu flood using the GAMA-1 and Nakayasu synthetic unit hydrographs

This study aims to find the most accurate method for predicting flood discharge in a watershed that does not have an automatic water level recorder and an automatic rainfall recorder. This research was conducted in the Air Bengkulu watershed, Indonesia. The method used is Nakayasu Synthetic Unit Hydrograph and GAMA-1. The results showed that the forecasting of flood discharge in the Air Bengkulu Watershed for various time returns, namely 2, 5, 10, 25, 50, and 100 years could use the Nakayasu and GAMA-1 Synthetic Unit Hydrograph Method. However, the value of the forecasting results of the two methods gives different results, for example, the discharge value for the 100-year time return in the Air Bengkulu Watershed. Therefore, it is necessary to validate the model if the results are used in decision making.