Landslide Hazard Mitigation for Sustainability Settlement in Maninjau Lake, West Sumatera

Abstract

The landslides around the Maninjau Caldera rim, particularly in the south, have posed a significant threat to lives over the years. Settlements nestled between Maninjau Lake, and the caldera wall are highly vulnerable to these hazards, and relocation is not feasible due to the scarcity of suitable land. The aim of study is to identify the safest area based on historical landslide data which is crucial for mitigation works in developing the Ngarai Sianok-Maninjau Geopark. This paper provides the affected delineation from the recent landslide compared to older events by identifying colluvial sediment and its morphological characteristics. The most recent major landslide occurred on July 13, 2023, in the Tanjung Raya District following heavy rainfall. The western and southern sections of the caldera rim, characterized by the steepest slopes, are most prone to landslides. Approximately 43 landslides with debris flow mechanisms along the inner caldera rim cover 3 villages (Nagari), namely Koto Malintang, Tanjung Sani, and Sungai Batang. Landslide debris in the southeast consists mainly of muddy sand, contrasting with the gravel and boulder sediment found elsewhere. All landslides originate in intermittent streams, creating sediment fans up to 50 meters wide downstream. Given this fan-shaped pattern, dispersed residential development is advisable over clustered housing, especially in Jorong (hamlet) Pantas, Nagari (village) Tanjung Sani. The high susceptibility of all drainage channels to landslides makes the main road vulnerable to disruption. Water transportation is strongly recommended as an alternative to prevent residents from becoming isolated if the main road is blocked.