/pdf/current-research-issues-related-to-post-wildfire-runoff-and-337eq10qjd.pdf

Current research issues related to post-wildfire runoff and erosion processes

Hydrologic and hydraulic effects of riparian root networks on streambank stability: is mechanical root-reinforcement the whole story?

This study compared lag time characteristics of low impact residential development with traditional residential development. Also compared were runoff volume, peak discharge, hydrograph kurtosis, runoff coefficient, and runoff threshold. Low impact development (LID) had a significantly greater centroid lag-to-peak, centroid lag, lag-to-peak, and peak lag-to-peak times than traditional development. Traditional development had a significantly greater depth of discharge and runoff coefficient than LID. The peak discharge in runoff from the traditional development was 1,100% greater than from the LID. The runoff threshold of the LID (6.0 mm) was 100% greater than the traditional development (3.0 mm). The hydrograph shape for the LID watershed had a negative value of kurtosis indicating a leptokurtic distribution, while traditional development had a positive value of kurtosis indicating a platykurtic distribution. The lag times of the LID were significantly greater than the traditional watershed for small (<25.4 mm) but not large (≥25.4 mm) storms; short duration (<4 h) but not long duration (≥4 h) storms; and low antecedent moisture condition (AMC; <25.4 mm) storms but not high AMC (≥25.4 mm) storms. This study indicates that LID resulted in lowered peak discharge depth, runoff coefficient, and discharge volume and increased lag times and runoff threshold compared with traditional residential development.

Comparison of Stormwater Lag Times for Low Impact and Traditional Residential Development

Rainfall-induced landslides are a common problem in residual soil slopes of the tropics. It is widely known that rainfall-induced slope failures are mainly caused by infiltration of rainwater; howe...

Response of a residual soil slope to rainfall

Rainfall is one of the most significant triggering factors for slope failures in many regions around the world. Numerous research studies have been conducted to investigate infiltration of rainwater into a slope, and the effect of water infiltration on slope stability. In this paper, a review of existing research on infiltration analysis and slope stability analysis under rainfall infiltration is presented. Studies on infiltration analysis with conceptual models, analytical analysis and numerical modelling are first reviewed. The typical pore water pressure profiles in the slope are then discussed. Subsequently, recent developments in analyses of slope instabilities under rainfall conditions using the limit equilibrium method and coupled hydro-mechanical modelling are summarised, and major findings on critical hydrological factors related to rainfall-induced landslides are summarised and discussed. Finally, several research topics are suggested for further study.

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Stability analysis of rainfall-induced slope failure: a review

Characteristics of residual soils in Singapore as formed by weathering

Effectiveness of horizontal drains for slope stability

Monitoring hydrologic responses of slopes is critical for advancing hillslope hydrologic studies. Storm- and time-based continuous hydrologic responses from three instrumented hillslopes in Singapore were monitored for a period of 420 days to observe the impact of rainfall on the pore-water pressure changes and runoff generation. Analyses of the hydrologic data indicate that only about 37% of the annual rainfall events are capable of producing runoff, and a threshold rainfall of about 10 mm is required to produce runoff. The seasonal distribution of pore-water pressures showed that the slopes experience high matric suctions during dry periods that are compa- rable to matric suctions observed in other tropical climates, and positive pore-water pressures during wet periods, that are higher than in other geographic locations. A high correlation between the increase in pore-water pressure and the daily rainfall may provide a convenient estimate of the increase in pore-water pressure due to the daily rainfall. The variability of hillslope hydrologic responses from storm to storm is distinctive when compared with previous results at other geographic locations.

Hydrologic Behavior of Residual Soil Slopes in Singapore

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 pore-water 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. Copyright © 2002 John Wiley & Sons, Ltd.

R. B. Rezaur

Papers

Response of a residual soil slope to rainfall

Characteristics of residual soils in Singapore as formed by weathering

Effectiveness of horizontal drains for slope stability

Hydrologic Behavior of Residual Soil Slopes in Singapore

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