Local Scour Analysis of Kuala Samboja Bridge Piers Kutai Kartanegara East Kalimantan

Kuala Samboja Bridge which has been built in 1992 and is located on Jalan Poros Balikpapan-Handil II, Samboja District, Kutai Kartanegara Regency. Cause of the flow of ship traffic under this bridge, the riverbed around the piers has the potential scouring. This study was conducted to determine the depth of local scour that occurs on the piers of the Kuala Samboja Bridge using several empirical equations. This study begins with collecting data on daily rainfall, maps of the Samboja River watershed, and measurement of river cross-section, flow rate and sampling of riverbed material. The dominant discharge was designed using the Nakayasu Unit Hydrograph. Testing the soil samples in the laboratory to obtain d50, an then predicting the local scour depth using the empirical method. The local scour depth was calculated using HEC-18, Froehlich, Laursen & Toch, and Salim & Jone. The shape of the piers analyzed is a group of cylindrical piers with a distance between piers of 1.2 m with a diameter of 0.5 m. The dominant discharge used is 401.203 m3 /second. The results of the calculation of the scour depth are as follows: the Froehlich method is 0.739 m, the HEC-18 method is 0.895 m, the Laursen & Toch method is 0.933 m, and the Salim & Jone methods are 0.675 m for the envelope curve, 0.54 m for the best fit curve.