Evaluation and Modification of a Sediment Excluder for Cohesive Sediment in Irrigation Areas in Indonesia: Field Evidence, Numerical Modeling, and Physical Model Validation

Herryan Kendra Kaharudin; Agustinus Purna Irawan; Wati A. Pranoto

doi:10.51988/jtsc.v7i4.748

Authors

Herryan Kendra Kaharudin Doctoral Program in Civil Engineering, Faculty of Engineering, Universitas Tarumanagara
Agustinus Purna Irawan Doctoral Program in Civil Engineering, Faculty of Engineering, Universitas Tarumanagara
Wati A. Pranoto Doctoral Program in Civil Engineering, Faculty of Engineering, Universitas Tarumanagara

DOI:

https://doi.org/10.51988/jtsc.v7i4.748

Keywords:

cohesive sediment, sediment excluder, Silt Settler, irrigation design criteria, FLOW-3D

Abstract

KP-02 and KP-04 provide sand traps and sediment excluders primarily intended for non-cohesive sediment, whereas many irrigation systems carry predominantly silt and clay. This study evaluates existing structures and develops a modified Silt Settler concept for cohesive sediment using field evidence, numerical modeling, and physical model validation. Samples downstream of the Warujayeng sediment excluder contained 74.6–75.0% silt and 21.0–21.8% clay. At Tami Weir, cohesive fractions in bed sediment reached 77–100%, with TSS concentrations of 130–270 mg/L. HEC-RAS 2D modeling showed that sediment concentration in the existing sand trap decreased from 380–427 mg/L to approximately 150 mg/L, but fine sediment continued to enter the main canal. Two four-channel Silt Settler alternatives were simulated using FLOW-3D Hydro and evaluated against Krone deposition and Partheniades erosion thresholds. At a settling discharge of 5.0 m³/s, the deposition-opportunity index was 0.48% for Alternative 2A and 0.02% for Alternative 2B. The inlet baffle in Alternative 2A increased the projected index to 56.4–58.0%. Validation using a 1:5 physical model produced MAPE values of 6.43% for water level and 12.50% for velocity. The results support Alternative 2A with an inlet baffle and measurable cohesive-sediment criteria for updating KP-04

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