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Landslide erosion risk to New Zealand pastoral steeplands productivity
Author(s) -
Luckman P. G.,
Gibson R. D.,
Derose R. C.
Publication year - 1999
Publication title -
land degradation and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.403
H-Index - 81
eISSN - 1099-145X
pISSN - 1085-3278
DOI - 10.1002/(sici)1099-145x(199901/02)10:1<49::aid-ldr320>3.0.co;2-j
Subject(s) - landslide , productivity , environmental science , erosion , terrain , natural hazard , storm , hydrology (agriculture) , physical geography , geography , geology , geomorphology , meteorology , geotechnical engineering , economics , macroeconomics , cartography
Pastoral land use in New Zealand's North Island hill terrain has led to high rates of rainstorm‐induced landslide erosion higher than existed under the indigenous forest regime, with consequent soil productivity declines in the long term. To assist extrapolation of research results to other areas, and to shed light on long‐term erosion risks, a simple model was developed that simulates the evolution of hillslope soil productivity, taking into account the effect of slope, rainstorm magnitude–frequency relations and soil recovery rates. Risks are evaluated by Monte Carlo simulation, and reflect parameter uncertainty as well as the natural randomness associated with climatic events. A sensitivity analysis showed that landslide risk was most affected by the rainfall threshold for landsliding, the mean of the extreme value distribution for annual maximum storm rainfall, and the maximum degree of recovery of pasture productivity following landsliding. Simulations suggest productivity stabilizes at a reduced level well before all steep terrain is affected by landsliding, and that subsequent expected landslide‐induced productivity declines are too slow to provide sufficient economic motivation for measures to prevent landslide damage. A refined model showed that long‐term average rates of productivity decline are sensitive to changes in recovery rates resulting from progressive removal of the soil resource. Charts summarizing simulation results can be used to estimate long‐term productivity declines. Copyright © 1999 John Wiley & Sons, Ltd.