Code River is one of the rivers in Yogyakarta. Based on the news in the online media Viva News in 2010 there has been a flood in the river Code after the eruption of Mount Merapi to carry sediment material from the eruption of Mount Merapi . The existence of settlements along the river, causing increased flooding potential harm and harm to the community around the banks of the River Code. To analyze the flood on the river Code can be done with the help of HEC RAS software and necessary geometrical data stream, the data stream hydraulics and river flood discharge data. Geometric data stream, derived from topographic measurements of the river. The data in the form of hydraulic roughness coefficient manning river reviewed. As for the flood discharge data based on method of Synthetic Unit Hydrograph Gama I at the return period of 20 and 100 years. From the simulation results using data return period flood discharge at 20 years and 100 years did not occur flood on river. This is not in accordance with the floods in 2010 that caused the difference cross section, where sediments of lava in 2010 is still high, while at the research has occurred in the riverbed degradation. While simulations using extreme rainfall of 280 mm, which occurs for 6 hours resulted in flood on the location of P88, P90, and P96. Location flooding is Tegalpanggung Village Danurejan District of Yogyakarta city is a residential area located on the banks of the River lowland Code. Based on the actual conditions at the location in the area once the floods and the government has done elevation embankment, but the results of monitoring by using the extreme flood discharges in the area still need the addition of high embankment in anticipation of flooding.