Identification of Hydrological Characteristics and Sediment Rates of Bird Feather-Type Watersheds with SWAT Model: Case Study of Bomo River of Banyuwangi

Banyuwangi Regency has many bird feather-type rivers due to topographic conditions which are the valleys of Mount Ijen and Mount Raung so that they shape an elongated radial watershed with extreme weather anomalies, high river flow velocity, and have great destructive power when floods occur. The purpose of the research was to identify the hydrological characteristics and sediment rates of bird feather-type watersheds in the Bomo River of Banyuwangi. SWAT modeling is needed to identify these hydrological characteristics and sediment rates, through a process of simulation and calibration with monthly discharge data and then determination of characteristics with the watershed shape factor and Nakayasu synthetic unit hydrograph analysis based on the α, Cs, and Ck coefficients. Hydrological characteristics of the Bomo watershed have an elongated radial shape, having a left-leaning flood hydrograph which indicates in the ascending part the peak discharge of the hydrograph was slow, but the decline downstream was rapid and lasted a long time with a value of α of 0.6, Cs of 1.53, Ck of 1.01–1.29, and have watershed shape factor (SF) of 0.71 with length factor (LF) of 0.071. SWAT modeling in the Bomo watershed resulted in a total annual average erosion rate of 10.83 t/ha and a sediment yield of 26.15 t/ha. The calibration results obtained an MAE value of 0.02; RMSE of 0.80, and a correlation of 0.66. Sediment load analysis is needed to determine sedimentation rates in bird feather-type watersheds that can risk flooding in downstream areas.