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Lahars at Merapi volcano, Central Java: an overview
Ist Teil von
Journal of volcanology and geothermal research, 2000-07, Vol.100 (1), p.423-456
Ort / Verlag
Elsevier B.V
Erscheinungsjahr
2000
Link zum Volltext
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
Merapi volcano, in Central Java, is one of the most active volcanoes in the world. At least 23 of the 61 reported eruptions since the mid-1500s have produced source deposits for lahars. The combined lahar deposits cover about 286
km
2 on the flanks and the surrounding piedmonts of the volcano. At Merapi, lahars are commonly rain-triggered by rainfalls having an average intensity of about 40
mm in 2
h. Most occur during the rainy season from November to April, and have average velocities of 5–7
m/s at 1000
m in elevation. A wide range of facies may be generated from a single flow, which may transform downvalley from debris flow to hyperconcentrated streamflow.
Because of the high frequency and magnitude of the lahar events, lahar-related hazards are high below about 450–600
m elevation in each of the 13 rivers which drain the volcano. Hazard-zone maps for lahar were produced by Pardyanto et al. (Volcanic hazard map, Merapi volcano, Central Java (1/100,000). Geol. Surv. of Indonesia, Bandung, II, 4, 1978) and the Japanese–Indonesian Cooperation Agency (Master plan for land conservation and volcanic debris control in the area of Mt Merapi, Jakarta, 1980), but these maps are of a very small scale to meet modern zoning requirements. More recently, a few large-scale maps (1/10,000- and 1/2000-scale) and risk assessments have been completed for a few critical river systems.