Rainfall threshold for triggering debris flow on Merapi volcano area, Yogyakarta, Indonesia

• Main Authors: Kusumawardani, Rini, Kurniadhi, Rizki, Mukhlisin, Muhammad, Legono, Djoko
• Format: Conference Proceeding
• Language: English
• Subjects: Debris flow; Grain size distribution; Gravel; Hazards; Measuring instruments; Parameters; Rainfall; Sedimentation; Soil investigations; Soil properties; Surface water; Volcanoes; Water depth; Water flow
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4976891

Eruption of Merapi volcano on 2010 produced around 130 million cubic meters of deposit material consisting of ash, sand, gravel, and stone. Potential hazards of Merapi eruption caused a massive damages and destructions for both of during and after eruption. Phenomenon of deposit material sedimentation in upstream area of volcano causes debris flow occurrences induced by heavy rainfall. Ranfall intensity and its duration are important parameters which trigger the occurrence of debris flow. Another important parameters that effect of debris flow initiation are slope angle, surface water flow level, sediment concentration, density of soil, soil shear angle, grain size distribution of sediment deposit. This paper investigated the influence of rainfall triggering the debris occurrences located in Putih River, Magelang. The soil properties were collected from the river, while the rainfall data was obtained from three rain gauge stations (i.e., Station Maron, Mranggen and Ngepos). The results revealed the intensity maximum rainfall which was more than 40 mm/hour triggered the debris flow in Putih River Merapi. While, the critical basic slope (θ) and water depth (ho) were variables that greatly affect Takahashi Equation to predict the incidence of debris flow.