Physical model experiments were conducted to observe the migration of light non-aqueous phase liquids (LNAPL) in a double-porosity soil medium. The double-porosity characteristics of the soil were simulated through aggregation of kaolin which resulted in well-defined intra-aggregate and inter-aggregate pores. Digital images were collected to monitor LNAPL (modeled by toluene) migration. A special experimental setup was developed to enable the instantaneous capture of the LNAPL migration around the whole soil column using a single digital camera. An image processing module was applied to the captured images and the results plotted using a surface mapping programme. Events observed during the duration of the experiments were discussed. It was found that the LNAPL flowed much faster in the aggregated soil as compared to a single-porosity soil. The wettability of the fluid and the capillary pressure characteristics were demonstrated to be influential factors in immiscible fluids migration when the soil fabric showed highly contrasting porosity values.
Early flood warnings are important to allow sufficient time for evacuation.Although warning systems are now in place, key questions remain as to their effectiveness in sending information to the public, which may in part depend on the media used. This paper assesses the effectiveness of warnings disseminated to the public for the December 2014 Kelantan Flood, Malaysia. The flood was the worst in decades making it an appropriate case study with which to assess public awareness and perceptions associated with flood warnings and their dissemination. The effectiveness of warnings issued via different media was assessed by questionnaire.Results show that 56% of respondents received warnings prior to the flood, a majority of them through television and information shared among the public.While the preferred medium of warning is not dependent on age, assessment of peoples' response to warnings shows that with increasing age responsiveness to orders and readiness to evacuate decreases. To increase the number of people receiving the warnings, short message service (SMS) communications sent from the authorities to a wider audience may be considered, as information shared among the public is observed to be most effective in reaching the greatest number of people. K E Y W O R D S community response, disaster management, effective flood warning, flood disaster
This paper investigates the phenomenon of light non-aqueous phase liquid (LNAPL) migration in double porosity soil. Investigation on the migration of LNAPL in double porosity soil was performed on aggregated kaolin using the digital image analysis. The photographic technique was used to capture the migration of LNAPL in aggregated soil samples. The captured digital images were fed through an image processing code to convert them to the hue-saturation-intensity (HSI) format which were subsequently used to plot the 2D LNAPL migration behaviour. The results of Experiment 1 and 2 show that the LNAPL moved downward faster when the moisture content increased. Another observation was that the kaolin granules started to disintegrate at a water content of 35%. In conclusion, using image analysis technique has enabled the researchers to monitor and visualize the LNAPL migration in the double porosity soil columns based on HSI values. The contour plots of HSI intensity value has provide detailed and useful information for future research.
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