The effect of riparian tree roots on the mass-stability of riverbanks

Plants interact with and modify the processes of riverbank erosion by altering bank hydrology, flow hydraulics and bank geotechnical properties. The physically based slope stability model GWEDGEM was used to assess how changes in bank geotechnical properties due to the roots of native Australian riparian trees affected the stability of bank sections surveyed along the Latrobe River. Modelling bank stability against mass failure with and without the reinforcing effects of River Red Gum (Eucalyptus camaldulensis) or Swamp Paperbark (Melaleuca ericifolia) indicates that root reinforcement of the bank substrate provides high levels of bank protection. The model indicates that the addition of root reinforcement to an otherwise unstable bank section can raise the factor of safety (Fs) from Fs = 1·0 up to about Fs = 1·6. The addition of roots to riverbanks improves stability even under worst-case hydrological conditions and is apparent over a range of bank geometries, varying with tree position. Trees growing close to potential failure plane locations, either low on the bank or on the floodplain, realize the greatest bank reinforcement. Copyright © 2000 John Wiley & Sons, Ltd.

[1]  H. Piégay,et al.  Bank erosion management based on geomorphological, ecological and economic criteria on the Galaure River, France , 1997 .

[2]  L. J. Waldron,et al.  The shear resistance of root-permeated homogeneous and stratified soil. , 1977 .

[3]  F. D. Shields,et al.  EFFECTS OF WOODY VEGETATION ON SANDY LEVEE INTEGRITY , 1992 .

[4]  S. K. Sarma.  A note on the stability analysis of slopes , 1987 .

[5]  N. R. Morgenstern,et al.  The Stability of a Slurry Trench in Cohesionless Soils , 1965 .

[6]  I. Rutherfurd,et al.  History and Effects of Channelisation on the Latrobe River, Victoria , 1995 .

[7]  Eric Spencer,et al.  THRUST LINE CRITERION IN EMBANKMENT STABILITY ANALYSIS , 1973 .

[8]  D. G. Fredlund,et al.  Slope stability analysis incorporating the effect of soil suction , 1987 .

[9]  C. Thorne,et al.  Stable Channels with Mobile Gravel Beds , 1986 .

[10]  A. W. Bishop,et al.  The Use of Pore-Pressure Coefficients in Practice , 1954 .

[11]  A. M. Osman,et al.  Riverbank Stability Analysis. II: Applications , 1988 .

[12]  D. Greenway,et al.  Vegetation and slope stability , 1987 .

[13]  E. Andrews.  Bed-material entrainment and hydraulic geometry of gravel-bed rivers in Colorado , 1984 .

[14]  L. Waldron,et al.  SOIL REINFORCEMENT BY ROOTS: CALCULATION OF INCREASED SOIL SHEAR RESISTANCE FROM ROOT PROPERTIES , 1981 .

[15]  C. O'loughlin.  The importance of root strength and deterioration rates upon edaphic stability in steepland forests , 1982 .

[16]  Dr. Wolfgang Böhm.  Methods of Studying Root Systems , 1979, Ecological Studies.

[17]  S. Darby,et al.  Development and Testing of Riverbank-Stability Analysis , 1996 .

[18]  E. J. Hickin,et al.  VEGETATION AND RIVER CHANNEL DYNAMICS , 1984 .

[19]  Aspects of alluvial river bank recession: some examples from the Niger delta , 1997 .

[20]  D. Fredlund,et al.  Comparison of slope stability methods of analysis , 1977 .

[21]  N. Morgenstern,et al.  The analysis of the stability of general slip surfaces , 1965 .

[22]  T. Wu,et al.  Strength of tree roots and landslides on Prince of Wales Island, Alaska , 1979 .

[23]  J. Michael Duncan,et al.  State-of-the-Art: Static Stability and Deformation Analysis , 1992 .

[24]  B. Abernethy,et al.  Where along a river's length will vegetation most effectively stabilise stream banks? , 1998 .

[25]  J. Pizzuto.  Bank erodibility of shallow sandbed streams , 1984 .

[26]  Norbert Moregenstern,et al.  Stability Charts for Earth Slopes During Rapid Drawdown , 1963 .