Comparison of the Nakayasu, gamma, and Snyder hydrograph model to determining flood water level for the early warning system in the Ciliwung river

Flood disasters can directly affect families living on riverbanks, which can cause physical damage and financial losses and also cause loss of human life. Floods can occur due to high rainfall intensity for a long time. In Indonesia, flooding frequently appears on the Ciliwung River, passing through a vital location as the nation’s capital. The global climate crisis indirectly affects changes in rainfall; from the analysis, the temperature rise of 1 °C causes an increase in 100 mm in the Ciliwung watershed, which further increases the risk of flooding, ng in the watershed year. The hydrograph unit is one way to estimate the flooding in a river due to rainfall. To analyze the hydrograph unit, it’s necessary to know the watershed characteristic, such as river length, number of river confluence, watershed area, and river basin. This parameter needs to be known to calculate the flood hydrograph. This study aims to determine the difference in flood travel time with various hydrograph methods, namely Gamma, Nakayasu, and Snyder, with a return period of 25 years, with each value are 268.72 m3/second, 256.25 m3/second, and 351.88 m3/second. Flood time travel is an analysis based on flood discharge are 4.55 hours, 4.67 hours, and 3.72 hours. The results can be used as a model to conduct an early warning system during floods in the Ciliwung River. From the results of the ANOVA test, it can be seen that the three methods are not significantly different.