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Landslide forensics assessment was conducted in Cimanggung, Sumedang with the aim of identifying the causes and processes of landslides to guide the critical step of future disaster prevention. The methodology includes investigations on geology, lithology, hydrology, land cover, land-use changes, and rainfall triggering the landslide. Unmanned Aerial Vehicles were used to investigate detailed spatial geomorphology for determining landslide development. The forensic assessment of the landslide that occurred in Cimanggung, Sumedang, on January 9, 2021, revealed the role of environmental changes. The conversion of open land to residential areas affects the water balance. The surface burden to the site on the hilltop by houses and toe-side cutting at the bottom of the slope has occurred. Changes in land conditions and hydrology, along with lithology thickness and variations, are essential aspects of the landslide incident. During the high rainfall rate, there is more water runoff, and the flow could be concentrated in a paleo channel formed by thicker unconsolidated sediments. The combination of these aspects destabilized the slope causing it to slide. Water management, particularly drainage improvement, should be established to prevent excessive runoff and centralized infiltration. Detailed hazard zonation, site delineation, and rainwater storage could be developed to avoid future landslides.

Landslides have occurred in various places in Indonesia. Likewise with West Java, there were many regions that has experienced repeated landslides. Having many experience of occurrences of landslides, we should have had a good landslide risk reduction program. Indeed, the incidence of landslides depends on many variables. Due to that condition, it may that a region would have different variable with another region. So it is impossible to generalize the implementation of a mitigation technology for all areas prone to landslides. Research of the Cililin's landslide is to anticipate the next disasters that may happen in around the area of 2013 Cililin Landslide. Through observation lithological conditions, water condition, land cover and landscape, as well as consideration of wide dimension of the building footing, the distance of building to the slopes and so forth, it has been determined some efforts of disaster risk reduction in the area around the landslide against the occurrence of potential landslide in the future.Bencana tanah longsor telah terjadi di berbagai tempat di Indonesia. Demikian halnya dengan Jawa Barat, tidak sedikit daerahnya telah berulang kali mengalami longsor. Seharusnya dengan telah banyaknya kejadian longsor, kita mampu mengupayakan program penurunan risiko longsor secara baik. Memang kejadian longsor bergantung pada banyak variabel, dimana dari satu daerah dengan daerah yang lain akan sangat memungkinkan mempunyai variabel yang berbeda, sehingga tidak mungkin kita membuat generalisasi penerapan suatu teknologi mitigasinya untuk semua daerah rawan longsor. Penelitian longsor di Cililin dilakukan untuk mengantisipasi terjadinya bencana di sekitar daerah Longsor Cililin 2013 yang lalu. Melalui pengamatan kondisi litologi, keairan, tutupan lahan dan bentang alam yang ada, serta pertimbangan akan dimensi luas pijakan bangunan, jarak batas bangunan dengan lereng dan lain sebagainya, telah ditentukan beberapa upaya penurunan risiko bencana di daerah sekitar longsor terhadap potensi kejadian longsor dimasa mendatang.Keywords: Landslide, risk reduction, footing of building, Cililin