Yosephina Puspa Setyoasri
Institut Teknologi Bandung

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Simulation of Design Flood Discharge under Projected Land Cover Scenarios Using ANN–MOLUSCE and HEC-HMS in the Cijangkelok Watershed Vika Febriyani; Yadi Suryadi; Tri Wahyudin Ahmad; Arief Yudho Wicaksono; Yosephina Puspa Setyoasri
Jurnal Teknik Pertanian Lampung (Journal of Agricultural Engineering) Vol. 15 No. 1 (2026): February 2026
Publisher : The University of Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jtepl.v15i1.419-430

Abstract

River flooding during rainy season is partly resulted from land cover changes. This study analyzes the impact of land cover changes on flood hydrographs using Curve Number (CN), Impervious (I), and Initial Abstraction (Ia). Land cover data (2009 and 2022) were obtained from the Ministry of Environment and Forestry, while the 2035 scenario was modeled with QGIS MOLUSCE (ANN). CN and I values were then applied in HEC-HMS simulations with SCS and Snyder Unit Hydrograph methods. Results show major land conversion by 2035 is particularly from dryland to rice fields, built-up areas, and forest plantations. The 2035 land cover prediction had minimum overall error of 0.0332 and Kappa coefficient of 0.765, indicating good model reliability. Composite CN increased from 67.9 (2009) to 68.0 (2022) and 68.4 (2035); I values from 5.6 to 5.7 and 6.4; while Ia decreased from 24.0 to 23.9 and 23.5 (2035). Flood discharges with the SCS method rise from 617.2 m³/s (2009) to 623.8 m³/s (2022) and 641.3 m³/s (2035), while the Snyder method produced 621.3, 621.6, and 630.5 m³/s. Statistical comparison between simulated and frequency-based design flood discharge results in PBIAS values of 0.1–0.2 (very good) and NSE of 1.0 (very good). The discharge increases of 1.1–2.8% indicate that land cover changes contribute to higher flood potential, but still in moderate level as most conversion is to rice fields, which function as temporary water storage and delay direct runoff.
Assessment of Flood Discharge Using the HSS SCS–CN Method and Implications for Adaptive Sabo Dam Design in the Saluki River Yosephina Puspa Setyoasri; Dantje Kardana Natakusumah; Vika Febriyani; Deddy Irwansyah
Jurnal Teknik Pertanian Lampung (Journal of Agricultural Engineering) Vol. 15 No. 2 (2026): April 2026
Publisher : The University of Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jtepl.v15i2.676-688

Abstract

In 2018, the Saluki River was morphologically altered due to 7.4 magnitude earthquake. The changes necessitated an evaluation of post-earthquake hydrological conditions prior to Sabo Dam planning. This study aims to estimate the design flood discharge and assess its implications for the preliminary design of a Sabo Dam in Saluki River. Design flood discharge was estimated using the Soil Conservation Service – Curve Number Synthetic Unit Hydrograph (SCS-CN) method. The model results were calibrated using bankfull discharge measured directly. A sensitivity analysis of the CN parameter was performed with ±10% variation to evaluate the effect of post-earthquake changes on peak flood discharge. The design flood discharge was 102.3 m³/s for the 2-year return period (Q2), 143.9 m³/s (Q5), 173.7 m³/s (Q10), 212.8 m³/s (Q25), 244.8 m³/s (Q50), and 272.8 m³/s (Q100). The SCS-CN simulation results deviate only 0.15% from the observed bankfull discharge, indicating that the selected hydrological parameters is in agreement with the characteristics of local rainfall-runoff process and catchment areas in the region. The sensitivity test revealed that a 10% increase in the CN value resulted in a 40% increase in the Q2 peak discharge, while a 10% decrease led to 30% reduction. The Q100 discharge of 272.8 m³/s was adopted as the capacity of Sabo Dam design. In conclusion, SCS–CN method remains applicable for watershed conditions analysis in areas which its morphological changes affected by earthquakes. However, the reliability of the model is constrained by limited field observations and potential uncertainties in CN parameter estimation.