2D Hydrodynamic Analysis Using HEC-RAS in the way Sulan Watershed

During the period 1991 to 1995, floods in Indonesia caused trillions of rupiah in losses with 4,246 deaths, 6,635 injuries, around 7 million people suffering and 324,559 houses damaged (BNPB, 2013). In Lampung Province, there are 3 (three) River Basin Units (SWS), those are: Mesuji-Tulang Bawang SWS, Seputih-Sekampung SWS and Semangka SWS. Of these three SWS Way Sulan is a tributary of the Way Sekampung, a river length of 46,24 km and a watershed area of ​​238,58 km 2 . This research uses HEC-RAS, Global Mapper, ArcGIS applications. The research method used is a flood inundation simulation using HEC-RAS with an unsteady flow type and displaying the simulation results on a race mapper. After going through several stages, the flood inundation area was obtained Q 2 = 248.74 km 2 , Q 5 = 257.59 km 2 , Q 10 = 263.07 km 2 , Q 20 = 267.49 km 2 , Q 25 = 268.32 km 2 , Q 50 = 271.92 km 2 , Q 100 = 274.14 km 2 , so that we get the equation of the relationship curve between maximum discharge and inundation area: y = 220.86 + 0.0331x with R2 = 0.998 and the equation of the relationship curve between maximum discharge and inundation height : y = 4,2043 + 0,1057x with R2 = 0,9337