On Dec 16, 1999, in the Corre Grande region of Venezuela, there was simultaneous debris discharge in 20 streams over a distance of 50 Kms. The damage was so profound that it destroyed 25,000 houses and damaged more than 65,000 houses. The total loss was estimated at $2billion U.S. dollars. In view of the largescale damage and loss inflicted by this natural calamity the Venezuelan government decided to collaborate with Chinese researchers in designing an appropriate debris hazard control mechanism. Such debris flow events following the sudden eruption of a dormant volcano is an event of common occurrence in many regions across the world. For example the May 27, 1984 debris flow totally destroyed the copper mining fields in the Yunnan province of China. Similarly, the debris flow along with the water from the melted ice (due to sudden volcanic eruption) completely inundated the town of Armero in Colombia killing more than 25,000 of its inhabitants. Volcanic debris flow hazard is more pronounced in areas with a steep topography and plenty of water and Cerro Grande happens to be one such geologically ideal location.
The author discusses various mechanical systems such as check dam, Trap slit dams with large windows, and drainage channels to be strategically placed to control debris flow. The researchers propose that using slit trip dams on strategic locations across the riverbed would help to control around 85% to 90% of the debri flow triggered by volcanic eruptions or due to rainstorms and landslides. The dam is made of concrete...
The design also includes 2 auxiliary dams placed at 40 and 70 m respectively from the main dam. Finally, a drainage channel carries the accumulated debris back into the sea. Thus by means of comprehensive mechanical systems such as slit trap dams, check dams and drainage channels it is possible to check the force of debris and to minimize the impact on the surrounding landscape. Debris flow can be either high frequency or low frequency. High frequency debris flow is usually initiated by sudden eruptions, earthquakes, etc. Even with continuous low frequency debris discharge, the ecosystem is considerably damaged and hence it is all the more necessary to install such preventive mechanisms. Therefore, it is clearly obvious that disaster management and prevention methods such as the ones described by the author are to be carefully studied and considered for implementation in volcanic prone regions in order to avoid or at least minimize human casualties and other damages.
Bibliography
Wang Shige, "Characteristics of Large Low-frequency Debris Flow Hazards and Mitigation Strategies," Journal of Mountain Science Vol 2 No 1 (2005): 50~58,
Available online at, http://www.imde.ac.cn/journal/Vol_04/p50-58.pdf
Ronald W. Perry, John David Godchaux, 'Volcano hazard management strategies',
Journal of Disaster Prevention and Management, Apr 2005 Volume: 14 Issue: 2-Page: 183-195
David…
