Journal of Marine-Earth Science and Technology

HYDRAULIC MODELING STUDY OF ALTERNATIVE FLOOD CONTROL STRATEGIES FOR THE REJOSO RIVER PASURUAN

2025-06-05T01:54:35+07:00

Rejoso River is administratively included in Pasuruan Regency where its watershed is located in 10 sub-districts (Puspo, Tosari, Gondang Wetan, Rejoso, Winongan, Pasrepan, Grati Districts of Pasuruan Regency and Lumbang, Sukapura, Probolinggo Regency). The area of the Rejoso River watershed is ± 361.2 km², bordered by hillsides and protected forests. In general, the cause of flooding in the Rejoso River watershed is caused by high intensity rainfall and changes in land use such as the Rejoso River, especially in the upstream area. The flat topography of the downstream area causes potential sedimentation which inhibits the flow (run off). The purpose of this study is to determine the condition of the existing system and capacity of the Rejoso River; to determine the influence of land use, and to provide alternative scenarios for the most effective flood control to reduce the flood water level or collect the flood that occurs. In this study, hydrological and hydraulic modeling was carried out. The method that used in the calculation of flood discharge is HEC-HMS, while for hydraulic analysis the HEC-RAS 1D is used with the results of water level at the river cross section. This analysis aims to determine the most effective flood control scenario for reducing flooding that occurs in the Rejoso River. The results of this study are alternative flood control scenarios for the Rejoso River by carrying out normalization, embankment’s structure and retention ponds which are the best scenarios for reducing high flood water levels. This can be shown by a decrease of average height of the flood water level from 1.207 meters to 0.435 meters. With these conditions, it can be concluded that this scenario is the best scenario for reducing the high flood overflow in the Rejoso River.

EVALUATION OF THE VIABILITY OF TARIFFS BASED ON TRANSPORTATION EXPENSES FOR CATAMARAN RIVER SERVICES ON THE PARANGLOE - LAKKANG ROUTE

2025-07-27T03:29:04+07:00

Establishing ship fares necessitates a thorough examination because it encompasses multiple cost factors, with fuel being the primary expense. For operators, it is crucial to determine fares that not only account for operational expenses but are also competitive and accessible for users of the service. This research investigates the viability of river transport fares using catamaran vessels on the Parangloe–Lakkang route, which can accommodate 12 passengers and 10 motorcycles, with a maximum of 8 vessels in operation. The aim of this research is to assess the minimum fare needed for the vessels to function sustainably by employing the Required Freight Rate (RFR) method, alongside evaluating passengers' ability and willingness to pay through the Ability to Pay (ATP) and Willingness to Pay (WTP) methodologies. The analysis reveals that the lowest minimum fare for passengers is Rp1.910/trip for vessel 3, while vessel 8 has the highest minimum fare at Rp2.442/trip. The ATP for passengers has been noted at Rp2.893/trip, whereas the WTP is recorded at Rp2.000/trip. These findings imply that the RFR fare falls between the WTP and ATP figures, indicating it is within a suitable range for fare policy. This result is significant as it provides a foundation for establishing sustainable fares and promotes enhancements in the quality of river transport services to ensure they are safer and more enjoyable for passengers.

SENSITIVITY ANALYSIS OF HYDROSTATIC PARAMETERS WITH RESPECT TO DISPLACEMENT CHANGES ON THE MINI BORNEO BARGE

2025-07-27T09:50:54+07:00

This study presents a systematic sensitivity analysis of key hydrostatic parameters, keel to buoyancy distance (KB), metacentric radius (BM), and metacentric height (GM), with respect to incremental changes in displacement for the Mini Borneo barge. Utilizing only the vessel’s official stability booklet data, natural cubic splines were fitted to the discrete hydrostatic tables to reconstruct continuous functions for each parameter over the displacement range of 256.6 t to 1641.0 t. First derivative functions were then derived analytically and cross-validated via centered finite difference, enabling high-resolution evaluation of ∂KB/∂Δ, ∂BM/∂Δ, and ∂GM/∂Δ at 0.01 t increments. Results indicate that KB sensitivity peaks at a moderate load of approximately 436.6 t (0.00045 m/t), whereas BM and GM sensitivities reach their maxima at full-load conditions near 1641.0 t (0.00086 m/t and 0.00092 m/t, respectively). Critical displacement intervals were identified around these peaks, highlighting narrow bands where small weight additions most profoundly affect stability. These findings inform the definition of safe-loading envelopes and ballast-management strategies, providing practical thresholds to maintain regulatory stability margins without the need for additional sea trials. The methodology is readily generalizable to other small craft equipped with hydrostatic booklets..

SEDIMENT TRANSPORT BEHAVIOUR IN A STRAIT UNDER THE INFLUENCE OF CURRENTS

2025-05-06T02:51:57+07:00

The Madura Strait, one of the most congested shipping lanes in Indonesia has been an important shipping route since the 13th century until recent days. The problem that exists in Madura strait is excessive sediment supply from river. This condition has disrupted several infrastructure facilities in the Madura Strait as happened at the Petrokimia Gresik port that is experiencing massive sedimentation. As one of the main supporting facilities in the factory, the existence and continuity of the port is important to always be maintained. This is related to the shallowing that often occurs in turning basin area. To estimate the shallowing process due to sedimentation in the pier pool, an analysis using a numerical model approach was applied. Based on the analysis, the current velocity in the turning basin area ranged from 0.10 to 0.20 m/s. In some conditions, the current velocity tends to approach 0 m/s which indicates a sedimentation zone was formed. Further, the analysis of bottom sediment movement shows the density of sediment material around the turning basin area ranged between 0.03 and 0.06 kg/m³. This condition leads seabed shallowing by 5.5 cm/month threatens navigability.