Modelling Debris Flow Runout: A Case Study on the Mesilau Watershed, Kundasang, Sabah

Abstract

Debris flows are among the fatal geological hazards in Malaysia, with 23 incidents recorded in the last two decades. To date, very few studies have been carried out to understand the debris flow processes, causes, and runouts nationwide. This study simulated the debris flow at the Mesilau watershed of Kundasang Sabah caused by the prolonged rainfall after the 2015 Ranau earthquake. Several interrelated processing platforms, such as ArcGIS, HEC-HMS, and HyperKANAKO, were used to extract the parameters, model the debris flow, and perform a sensitivity analysis to achieve the best-fit debris flow runout. The debris flow travelled at least 18.6 km to the Liwagu Dam. The best-fit runout suggested that the average velocity was 12.5 m/s and the lead time to arrive at the Mesilau village was 4.5 min. This high debris flow velocity was probably due to the high-water content from the watershed baseflow with a discharge rate of 563.8 m3/s. The flow depth and depositional thickness were both lower than 5.0 m. This study could provide crucial inputs for designing an early warning system, improving risk communication, and strengthening the local disaster risk reduction and resilience strategy in a tectonically active area in Malaysia.

Landslides triggered by the 2015 Mw 6.0 Sabah (Malaysia) earthquake: inventory and ESI-07 intensity assignment

“…The landslide deposits provided abundant sediments for subsequent remobilization as debris flows following heavy rainfall (highest rainfall intensity of 14.2 mm h −1 on 15 June 2015; Rosli et al, 2021a). Some detailed studies of debris flows were performed on limited areas through lidar techniques (Yusoff et al, 2016;Rosli et al, 2021a, b), but a comprehensive inventory of all the triggered landslides is still lacking and is the focus of this paper.…”

“…The identification of the precise event that triggered the landslides can be challenging, and subsequent remobilizations may occur as well. In the Sabah case, slope movements were firstly triggered by the seismic shaking; later on, prolonged rainfall reactivated the landslide deposits as debris flows (Rosli et al, 2021a). In this work, landslides were mapped on optical satellite images, whose availability depends on satellite revisit time and local weather conditions.…”

Assessment of immediate and five-year earthquake impacts on river systems in sabah, Malaysia using multi-temporal satellite imageries

“…This seismic event continued for approximately 30 s. It was detectable as far as 400 km from the epicentre, which, situated nearly 10 km deep, was the most significant earthquake in Malaysia since the Mw 6.2 Lahad Datu earthquake in 1976 (Adnan and Harith 2017;Tongkul 2016). According to Rosli et al (2021), the primary hazard of the earthquake involved direct geological failures, which was observed at the foot slope of Mount Kinabalu, the tallest mountain in the region and the centrepiece of Kinabalu Park (UNESCO World Heritage Site. Widespread rockfalls and numerous landslides were triggered by the mainshock and a series of aftershocks near Mount Kinabalu, forming a temporary landslide dam.…”

“…The secondary hazard identified as debris flow occurred along the river channels. Rosli et al (2021) reported two debris flows, i.e. the Mesilau watershed of Kundasang on the Southeast flank of Mount Kinabalu and the Kadamaian watershed of Kota Belud, located on the northwest flank of Kota Belud.…”

Effect of Debris Flow Event on the Affected Areas in Putih River, Indonesia

“…Several researchers have also developed models for debris flow similar to the SIMLAR, such as HyperKanako [18,19] Flo-2D [20], RAMMS [19,20] Flow-R [21], and DebrisFlow Predictor [22]. Takebayashi and Fujita developed a model for debris flow based on a two-dimensional continuum body model [23].…”