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Investigation of the origin and magnitude of debris flows from the Payhua Creek basin, Matucana area, Huarochirí Province, Perú
Landslide Risk Management.London, 2005.
The small city of Matucana (population 5800), Province of Huarochirí, Perú is located on the flood plain of Rimac River in Andes Occidental, approximately 75 km east of Lima at an elevation of 2390 m (area of 11° 50.489’ S, 76° 22.857’ W). Adjacent ridges and mountain peaks rise to 5000 m. Matucana shares a 300m wide valley bottom with two transportation arteries: Carretera Central, the only highway in Perú connecting the Amazon basin to the Pacific Coast and Ferrocarril Central, the highest standard gauge railway in the world which services mines and communities in the Andes. The present course of Rimac River is controlled by a dike and fill for the highway and railroad. These structures confine it to the northern portion of its flood plain. Consequently, parts of Matucana are lower in elevation than the bed of Rimac River. Payhua Creek (PC), a steep, debris-flow-prone tributary to Rimac River, has built an extensive fan at the upstream end of the city. Debris flows from PC has dammed Rimac River and diverted it into Matucana. This type of disaster occurred 1959 and 1983 when heavy precipitation occurred in the normally arid Andes Occidental. The 1959 event was particularly notable as it destroyed 90% of Matucana with loss of life. Although these events were not well documented, investigation of the PC fan and documentation of 1983 deposits on the fan indicate that the 1983 debris flow had a volume in the 0.12 106 to 106m3 range. Investigation of surficial and bedrock geology including mapping of all landslides in PC basin was carried out in 2004. A landslide complex immediately west of Payhua village is the most significant source of debris flow sediment in the basin. Incision of an unfavourable succession of andesite flows overlying a pervasively fractured tuff is responsible for the concentration of landslides in the Payhua village area. The area affected by landsliding in this area has increased by a factor of five since 1951. The PC basin upstream from Payhua has been a relatively small source of debris flows during the past 600 to 800 years based upon archaeological evidence. Exposures of debris flow deposits in the PC fan indicate that debris flow events larger than those of 1959 and 1983 have occurred in the recent geologic past. Matucana has also grown significantly since 1983 and has further encroached on the Rimac River flood plain and the PC fan. As a result, if debris flows of the magnitude of those in 1959 and 1983 occur, direct burial of the upstream area of Matucana by debris flows is likely.
Taylor & Francis
Fídel, L.; Guzmán, A.; Zegarra, J.; Vílchez, M.; Colque, J. & Jackson, L.E., Jr. (2005). Investigation of the origin and magnitude of debris flows from the Payhua Creek basin, Matucana area, Huarochirí Province, Perú. In: Landslide Risk Management. London: Taylor & Francis, p. 467-473. DOI: 10.1201/9781439833711
Páginas 467-473. | Trabajo presentado en The International Conference on Landslide Risk Management, realizado en Vancouver, Canada, de 31 mayo a 3 junio, 2005.

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