Pemodelan Aliran dan Distribusi Lahar Gunung Slamet Di Lembah Guci
HIKMATUL NUR AFIFAH, Prof. Dr. Ir. Agung Harijoko, S.T., M.Eng., IPM.; Dr. Ir. Haryo Edi Wibowo, S.T., M.Sc.
2024 | Skripsi | TEKNIK GEOLOGI
Kawasan
Wisata Guci berada di Lembah Guci, sisi barat laut Gunung Slamet. Kawasan ini dikunjungi oleh ratusan ribu
wisatawan setiap tahunnya karena terkenal akan wisata pemandian air panas yang
bersumber dari hulu Sungai Gung. Oleh karena itu, banyak objek wisata dan hotel
yang dibangun di sekitar aliran Sungai Gung. Tingginya aktivitas manusia di
sekitar aliran Sungai Gung meningkatkan paparan risiko bahaya letusan gunungapi
salah satunya, yaitu bahaya lahar. Lahar dapat mengalir melewati sungai-sungai
di lembah gunungapi. Oleh karena itu, sebagai upaya mitigasi, perlu diketahui
mekanisme aliran lahar serta model sebaran area landaan lahar di daerah
penelitian.
Penelitian ini
menggunakan metode pengamatan lapangan, analisis granulometri terhadap matriks
endapan lahar, analisis variasi komponen endapan lahar, dan pemodelan area
landaan lahar dengan fitur Laharz pada perangkat lunak ArcMap menggunakan
skenario volume lahar 34.000 m3, 340.000 m3, 500.000 m3,
600.000 m3, 700.000 m3, 800.000 m3, 900.000 m3,
dan 1.000.000 m3. Endapan lahar di daerah penelitian
diklasifikasikan menjadi lahar tua dan lahar muda. Karakteristik endapan lahar
berdasarkan pengamatan lapangan, analisis variasi komponen endapan lahar, dan
analisis granulometri menunjukkan struktur masif, tidak ditemukan stratifikasi
atau imbrikasi; variasi komponen endapan lahar secara umum memiliki fragmen
heterogen dan matriksnya tersusun atas litik, skoria, mineral, material
lempung, dan tuf; kandungan bahan halus (lanau-lempung) < 5>
The
Guci Tourism Area is located in the Guci Valley, on the northwestern slope of
Mount Slamet. This area attracts hundreds of thousands of visitors annually,
renowned for its hot springs sourced from the headwaters of the Gung River.
Consequently, numerous tourist attractions and hotels have been developed along
the Gung River. However, the high level of human activity around the river
increases exposure to volcanic eruption hazards, particularly the risk of
lahars. Lahars can flow through rivers in volcanic valleys, making it crucial
to understand their characteristics, flow mechanisms, and the potential
inundation areas in the study region for effective mitigation.
This research uses field
observation methods, granulometric analysis of lahar deposit matrices, analysis
of lahar deposit component variations, and lahar inundation area modeling using
the Laharz feature in ArcMap software. The modeling was conducted with lahar
volume scenarios of 34,000 m³, 340,000 m³, 500,000 m³, 600,000 m³, 700,000 m³,
800,000 m³, 900,000 m³, and 1,000,000 m³. The lahar deposits in the study area
are classified as old lahar and young lahar. Based on field observations, lahar
deposit component variation analysis, and granulometric analysis, the lahar
deposits have a massive structure with no stratification or imbrication. The
lahar deposit components generally consist of heterogeneous fragments, with the
matrix composed of lithics, scoria, minerals, clay material, and tuff. Fine
material content (silt-clay) is less than 5% in the young lahar deposits. Based
on these characteristics, the lahar flow mechanism in the study area is
classified as non-cohesive debris flow, which has high density and is erosive,
resulting in significant destructive potential. The granulometric analysis of
the young lahar deposits shows a linear trend and a uniform grain size
classification. This suggests that there has been no transformation in the flow
mechanism of the young lahar within the 1.3 km transport distance. The lahar
inundation area model using the Laharz feature shows that lahar flows are
concentrated along the Gung River, which can impact the Guci tourist area,
agricultural land, and forest/shrub areas. The Gung River valley's deep
morphology limits the lahar's lateral spread compared to its horizontal
(longitudinal) spread. As the lahar volume increases, the inundation area
expands, raising the risk of material losses in affected areas.
Kata Kunci : Lahar, Lembah Guci, analisis granulometri, Laharz, mitigasi.