Spatial and temporal variability of pore-water pressures in residual soil slopes in a tropical climate

Abstract

It is critical to understand and quantify the temporal and spatial variability in hillslope hydrological data in order

to advance hillslope hydrological studies, evaluate distributed parameter hydrological models, analyse variability in

hydrological response of slopes and design efficient field data sampling networks. The spatial and temporal variability

of field-measured pore-water pressures in three residual soil slopes in Singapore was investigated using geostatistical

methods. Parameters of the semivariograms, namely the range, sill and nugget effect, revealed interesting insights into

the spatial structure of the temporal situation of pore-water pressures in the slopes. While informative, mean estimates

have been shown to be inadequate for modelling purposes, indicator semivariograms together with mean prediction by

kriging provide a better form of model input. Results also indicate that significant temporal and spatial variability in porewater

pressures exists in the slope profile and thereby induces variability in hydrological response of the slope. Spatial

and temporal variability in pore-water pressure decreases with increasing soil depth. The variability decreases during wet

conditions as the slope approaches near saturation and the variability increases with high matric suction development

following rainfall periods. Variability in pore-water pressures is greatest at shallow depths and near the slope crest and

is strongly influenced by the combined action of microclimate, vegetation and soil properties.