Landslides in Rio de Janeiro: The role played by variations in soil hydraulic conductivity

✍ Scribed by Bianca Carvalho Vieira; Nelson Ferreira Fernandes

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 671 KB
• Volume: 18
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/hyp.1363

✦ Synopsis

Abstract

Landslides are natural processes triggered by complex relationships between many conditioning factors. In Rio de Janeiro city, intense rainstorms combined with steep slopes, usually occupied by slums, create favourable conditions for landslide generation. In general, slope failures are related to high positive pore‐pressures inside soil mantles, which are associated with topographic hollows and hydraulic discontinuities inside the deep weathered profile.

This study aims to characterize the role played by spatial variations in saturated soil hydraulic conductivity K~sat~ on landsliding in the Papagaio Basin (2·5 km^2^), triggered by intense rainstorms (250 mm in less than 2 days) in February 1996. Field measurements, using the Guelph permeameter, were conducted along soil profiles (up to 5·0 m depth), around and inside landslide scars representing different geomorphological domains. Also, soil physical properties (grain size, total porosity, macroporosity, microporosity, etc.) were evaluated at the 87 sites where K~sat~ was measured.

Despite the many geological and pedological variations inside the basin, including changes in lithology, fracture density, vegetation type and succession stage, soil characteristics and weathering stage, and human activities, 94% of the K~sat~ values varied by only two orders of magnitude (1·0 × 10^−6^–9·0 × 10^−5^ m s^−1^). However, abrupt changes in K~sat~ were observed along some of the soil profiles studied, e.g. an increase of two orders of magnitude in only 0·30 m. These hydraulic discontinuities may contribute locally to the development of high pore pressures during intense rainstorms, leading to landsliding. The results also suggest that different K~sat~ variation patterns coexist inside the basin, which should be considered in mathematical models of landslide prediction. Copyright © 2004 John Wiley & Sons, Ltd.