<P dir=ltr style="mso-outline-level: 3" align=left><FONT face="Times New Roman"><SPAN style="FONT-SIZE: 18pt">A geomorphological assessment of landslide origin at </SPAN><?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:sm

18 March 2004 | 04:35 Code : 3671 Geoscience events
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<P dir=ltr align=left><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: FA">on the south coast of </SPAN><?xml:namespace pref

Bukavu, on the south coast of <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Lake Kivu in the Democratic Republic of the Congo, suffers from slow but never ending landsliding. This leads to the continuous degradation and destruction of houses, buildings and of the roads, waterworks and sewerage infrastructure in several districts of the town.Research of mass-wasting processes is hampered by the limited geotechnical and hydrogeological information concerning the deeply weathered Tertiary and Quaternary lavas. There is also a disagreement about the exact location of active faults, believed to play a role in the mass wasting. Additionally, there is little information about the exact location and the rate of soil movements and whether ground instability is caused by tectonics and seismics or by increase in hydrostatic pressure.Based on aerial photographic interpretation, landslides cover more than 15% of the town of Bukavu.Thirty-one landslides occur outside the Bukavu "microrift" and do not contact active faults. Rather, they occur in actively incising river basins, ostensibly caused by neotectonic activity.Four from the six landslides within the "micrograben" are bigger and wider than the others, apparently governed by pre-existing tectonically induced landforms. They are adjacent to or crossed by active faults. They also fall far below the envelope of topographic thresholds for landslides established for North America and verified in Rwanda.Therefore, this threshold, a combination of slope at the head of the slide and surface drained to it, seems a promising tool to discriminate hydrologically from tectonically seismically induced landslides. Recent soil movements in Bukavu generally correspond to landslide distribution portrayed on the geomorphologic map. Most Bukavu soil movements occur on previous slides. Therefore, from an engineering–geologic standpoint, old landslides should be avoided, or, if economically feasible, be mitigated.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

tags: QAZVIN


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