Electronic Theses and Dissertation

Tangkahan, Kecamatan Batang Serangan, Kabupaten Langkat, Provinsi Sumatra Utara, merupakan daerah ekowisata yang terletak di jalur Pegunungan Bukit Barisan. Wilayah ini memiliki potensi longsor yang tinggi akibat kondisi geomorfologi dan geologi yang kompleks, curah hujan yang relatif tinggi, serta keberadaan lereng yang curam. Penelitian ini bertujuan untuk mengetahui kondisi geologi yang meliputi litologi penyususn, struktur geologi, dan karakteristik geomorfologi, kualitas massa batuan, tingkat kestabilan lereng serta tipe longsoran di daerah penelitian. Metode yang digunakan meliputi pemetaan geologi dan geomorfologi, analisis kinematika lereng, serta klasifikasi Rock Mass Rating (RMR) dan Slope Mass Rating (SMR). Hasil pemetaan geologi menunjukkan bahwa satuan batuan di daerah penelitian, yang diurutkan dari tua ke muda, terdiri atas satuan batu serpih Baong, batu lempung Baong, dan endapan aluvial. Namun, berdasarkan data sekunder Cameron et al. (1982),menyebutkan bahwa Formasi Bruksah juga tersusun atas satuan batu pasir dan konglomerat. Secara geomorfologi, wilayah penelitian tersusun atas tiga satuan bentang alam utama, yaitu struktural, denudasional, dan fluvial. Bentang alam struktural dicirikan oleh perbukitan tinggi, bentang alam denudasional oleh perbukitan rendah hingga dataran denudasional, sedangkan bentang alam fluvial oleh tubuh sungai dan dataran banjir dengan pola aliran dendritik. Klasifikasi RMR menghasilkan nilai berkisar antara 45 hingga 61 yang menunjukkan kualitas massa batuan sedang, sedangkan analisis SMR menghasilkan nilai berkisar antara 56 hingga 76 yang mengindikasikan kondisi lereng tergolong baik, dengan potensi longsoran guling (toppling failure). Upaya mitigasi yang direkomendasikan meliputi pembuatan parit drainase pada kaki lereng, pemasangan jala kawat, pagar pengaman, serta baut batuan (rock bolt) untuk meningkatkan kestabilan lereng dan keselamatan kawasan.

Tangkahan, Batang Serangan District, Langkat Regency, North Sumatra Province, is an ecotourism area located along the Bukit Barisan Mountain Range. This area has a high landslide potential due to complex geomorphological and geological conditions, relatively high rainfall, and the presence of steep slopes. This study aims to determine the geological conditions of the study area, including lithological composition, geological structures, and geomorphological characteristics, as well as rock mass quality, slope stability levels, and types of landslides. The methods employed include geological and geomorphological mapping, slope kinematic analysis, and rock mass classification using the Rock Mass Rating (RMR) and Slope Mass Rating (SMR) systems. The results of geological mapping indicate that the rock units in the study area, arranged from oldest to youngest, consist of the Baong Shale Unit, the Baong Claystone Unit, and alluvial deposits. However, based on secondary data from Cameron et al. (1982), the Bruksah Formation is also reported to be composed of sandstone and conglomerate units. Geomorphologically, the study area is composed of three main landform units, namely structural, denudational, and fluvial landforms. Structural landforms are characterized by high hills, denudational landforms by low hills to denudational plains, while fluvial landforms are characterized by river channels and floodplains with a dendritic drainage pattern. The RMR classification yields values ranging from 45 to 61, indicating fair rock mass quality, while the SMR analysis produces values ranging from 56 to 76, suggesting generally stable slope conditions with a potential for toppling failure. Recommended mitigation measures include the construction of drainage ditches at the slope toe, installation of wire mesh, safety fences, and rock bolts to enhance slope stability and ensure the safety of the area.