# Integrated Sentinel-2 LULC, SCS-CN, and HEC-HMS analysis of hydrological response changes in the Ake Kobe Watershed, Indonesia 2019–2024
> Miradj A.

URL kanonis: https://discover.unhas.ac.id/publications/pub_scopus_105047831584
Jurnal / Konferensi: Frontiers in Built Environment
Tahun terbit: 2026
DOI: https://doi.org/10.3389/fbuil.2026.1876094
ISSN: 22973362
Kuartil SJR: Q1
Citations: 0

## Authors
- Miradj A.

## Abstract
This study quantifies the hydrological impacts of land use and land cover (LULC) change on the Ake Kobe Watershed (792.54 km 2 , Halmahera, North Maluku, Indonesia) between 2019 and 2024, coinciding with rapid industrial estate development in eastern Indonesia. Annual LULC maps were produced from Sentinel-2 imagery using a Random Forest classifier on Google Earth Engine, achieving an Overall Accuracy of 90.0% and a Kappa coefficient of 0.875, confirmed across 80/20, 70/30, and 60/40 training-testing splits. Reference samples were generated through systematic visual interpretation of Sentinel-2 composites cross-referenced with Google Earth high-resolution imagery and available regional land-use maps. Between 2019 and 2024, the watershed experienced substantial LULC transformation: forest cover declined by 4.85%, while industrial areas expanded by 638.8%, bare land by 127.9%, and built-up areas by 123.3%. GIS-based overlay of LULC and Hydrologic Soil Group maps produced composite Curve Numbers (CN) for nine sub-watersheds following USDA-NRCS TR-55 procedures; the area-weighted composite CN increased from 73.32 to 80.36 (+9.59%). SCS lag times were computed using the NRCS (2010) corrected formula Tlag = [L^0.8(S+1)^0.7]/[1900×Y^0.5] (L in feet, S in inches, Y in percent), yielding physically plausible lag values of 47.5–235.9 min. Design rainfall for a 25-year return period (166.92 mm, 24-h, SCS Type II) was determined via Gumbel frequency analysis, validated by Kolmogorov–Smirnov test. Under the 25-year design storm, scenario-based simulations—presented as uncalibrated comparative scenario estimates given the absence of an independent streamflow gauge—showed that 2024 LULC conditions produced a 49.13% increase in outlet peak discharge (from 3,176.49 to 4,737.15 m 3 /s), a 20.42% increase in direct runoff volume, and a 30-min acceleration in time-to-peak. These findings demonstrate that industrial expansion and deforestation have significantly increased flood hazard in the Ake Kobe Watershed. The integrated Sentinel-2, SCS-CN, and HEC-HMS framework provides a reproducible baseline approach for hydrological impact assessment in data-sparse, rapidly industrializing tropical watersheds, against which future studies employing machine learning-enhanced or uncertainty-aware modeling frameworks may be benchmarked.

## Keywords
- Land cover
- Watershed
- Environmental science
- Hydrology (agriculture)
- Gumbel distribution
- Land use
- Physical geography
- Streamflow
- Lag
- Satellite imagery
- Change detection
- Digital elevation model
- Cohen's kappa
- Remote sensing
- Visual inspection
- Forest cover
- Geology
- Geography
- Random forest
- Typhoon
- Water level
- Infiltration (HVAC)
- Driving factors
- Vegetation (pathology)

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Sumber: Discover Unhas — RIMS Universitas Hasanuddin.
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