Wan Nor Azmin Sulaiman

An artificial neural network model for flood simulation using GIS: Johor River Basin, Malaysia

Flooding is one of the most destructive natural hazards that cause damage to both life and property every year, and therefore the development of flood model to determine inundation area in watersheds is important for decision makers. In recent years, data mining approaches such as artificial neural network (ANN) techniques are being increasingly used for flood modeling. Previously, this ANN method was frequently used for hydrological and flood modeling by taking rainfall as input and runoff data as output, usually without taking into consideration of other flood causative factors. The specific objective of this study is to develop a flood model using various flood causative factors using ANN techniques and geographic information system (GIS) to modeling and simulate flood-prone areas in the southern part of Peninsular Malaysia. The ANN model for this study was developed in MATLAB using seven flood causative factors. Relevant thematic layers (including rainfall, slope, elevation, flow accumulation, soil, land use, and geology) are generated using GIS, remote sensing data, and field surveys. In the context of objective weight assignments, the ANN is used to directly produce water levels and then the flood map is constructed in GIS. To measure the performance of the model, four criteria performances, including a coefficient of determination (R2), the sum squared error, the mean square error, and the root mean square error are used. The verification results showed satisfactory agreement between the predicted and the real hydrological records. The results of this study could be used to help local and national government plan for the future and develop appropriate (to the local environmental conditions) new infrastructure to protect the lives and property of the people of Johor.

A knowledge-driven GIS modeling technique for groundwater potential mapping at the Upper Langat Basin, Malaysia

The aim of this paper is to use a knowledge-driven expert-based geographical information system (GIS) model coupling with remote-sensing-derived parameters for groundwater potential mapping in an area of the Upper Langat Basin, Malaysia. In this study, nine groundwater storage controlling parameters that affect groundwater occurrences are derived from remotely sensed imagery, available maps, and associated databases. Those parameters are: lithology, slope, lineament, land use, soil, rainfall, drainage density, elevation, and geomorphology. Then the parameter layers were integrated and modeled using a knowledge-driven GIS of weighted linear combination. The weightage and score for each parameter and their classes are based on the Malaysian groundwater expert opinion survey. The predicted groundwater potential map was classified into four distinct zones based on the classification scheme designed by Department of Minerals and Geoscience Malaysia (JMG). The results showed that about 17% of the study area falls under low-potential zone, with 66% on moderate-potential zone, 15% with high-potential zone, and only 0.45% falls under very-high-potential zone. The results obtained in this study were validated with the groundwater borehole wells data compiled by the JMG and showed 76% of prediction accuracy. In addition statistical analysis indicated that hard rock dominant of the study area is controlled by secondary porosity such as distance from lineament and density of lineament. There are high correlations between area percentage of predicted groundwater potential zones and groundwater well yield. Results obtained from this study can be useful for future planning of groundwater exploration, planning and development by related agencies in Malaysia which provide a rapid method and reduce cost as well as less time consuming. The results may be also transferable to other areas of similar hydrological characteristics.

Identification of the Hydrogeochemical Processes in Groundwater Using Classic Integrated Geochemical Methods and Geostatistical Techniques, in Amol-Babol Plain, Iran

Hydrogeochemical investigations had been carried out at the Amol-Babol Plain in the north of Iran. Geochemical processes and factors controlling the groundwater chemistry are identified based on the combination of classic geochemical methods with geographic information system (GIS) and geostatistical techniques. The results of the ionic ratios and Gibbs plots show that water rock interaction mechanisms, followed by cation exchange, and dissolution of carbonate and silicate minerals have influenced the groundwater chemistry in the study area. The hydrogeochemical characteristics of groundwater show a shift from low mineralized Ca-HCO3, Ca-Na-HCO3, and Ca-Cl water types to high mineralized Na-Cl water type. Three classes, namely, C1, C2, and C3, have been classified using cluster analysis. The spatial distribution maps of Na+/Cl−, Mg2+/Ca2+, and Cl−/HCO3 − ratios and electrical conductivity values indicate that the carbonate and weathering of silicate minerals played a significant role in the groundwater chemistry on the southern and western sides of the plain. However, salinization process had increased due to the influence of the evaporation-precipitation process towards the north-eastern side of the study area.

Extent and severity of groundwater contamination based on hydrochemistry mechanism of sandy tropical coastal aquifer.

Small islands are susceptible to anthropogenic and natural activities, especially in respect of their freshwater supply. The freshwater supply in small islands may be threatened by the encroachment of seawater into freshwater aquifers, usually caused by over pumping. This study focused on the hydrochemistry of the Kapas Island aquifer, which controls the groundwater composition. Groundwater samples were taken from six constructed boreholes for the analysis and measurement of its in-situ and major ions. The experimental results show a positive and significant correlation between Na-Cl (r=0.907; p<0.01), which can be defined as the effect of salinization. The mechanisms involved in groundwater chemistry changes were ion exchange and mineralization. These processes can be demonstrated using Pipers diagram in which the water type has shifted into a Na-HCO(3) water type from a Ca-HCO(3) water type. Saturation indices have been calculated in order to determine the saturation condition related to dissolution or the precipitation state of the aquifer bedrock. About 76% of collected data (n=108) were found to be in the dissolution process of carbonate minerals. Moreover, the correlation between total CEC and Ca shows a positive and strong relationship (r=0.995; p<0.01). This indicates that the major mineral component in Kapas Island is Ca ion, which contributes to the groundwater chemical composition. The output of this research explains the chemical mechanism attributed to the groundwater condition of the Kapas Island aquifer.

Groundwater irrigation quality mapping using geostatistical techniques in Amol–Babol Plain, Iran

Groundwater is acknowledged to be a reliable source for agricultural activities in arid and semi-arid regions. An assessment of the suitability of groundwater for agricultural usage was carried out on the Amol–Babol Plain, Iran, where agriculture is the dominant economic activity. Groundwater samples were collected from 154 wells during the wet and dry seasons in 2009. The sodium percentage, sodium adsorption ratio, residual sodium carbonate, magnesium hazard, and Kelly’s ratios were used as indicators for the water quality. Geostatistical technique of ordinary kriging method was used to create spatial distribution maps. The thematic maps of salinity hazard, sodium adsorption ratio, and sodium percentage indicated an increasing trend of concentration from the western and southern areas to the east and north-east of the plain. The maps also show that the groundwater quality decreases gradually from the west and south sides to the north-eastern side. There is also no significant change in seasonal variation of water quality parameters.

GIS DRASTIC model for groundwater vulnerability estimation of Astaneh-Kouchesfahan Plain, Northern Iran.

In this study, the groundwater vulnerability to pollution was evaluated for Astaneh-Kouchesfahan Plain, Northern Iran using GIS DRASTIC model. Based upon available data, six thematic maps were generated and intrinsic vulnerability map was developed based upon calculations from various mapped layers and DRASTIC index. The results show that low, moderate, high and very high groundwater vulnerability risk zones cover around 12, 52, 28 and 8% of the area, respectively. Finally, in order to verify the model, the categorised DRASTIC map was compared with a categorized TDS map and the results shows that the areas including enhanced values of TDS correspond with those with higher DRASTIC ratings.

Open source geographical resources analysis support system (GRASS) for landslide hazard assessment

Purpose – The primary aim of this research is to investigate the application of open source geographic information system software, geographical resources analysis support system (GRASS) for landslide hazard assessment.Design/methodology/approach – Five parameters affecting landslide occurrence derived from topographical, geological and land use maps of Cameron highland were used for the assessment.Findings – The results showed that about 93 percent of the study area falls under zone II that is of low hazard, with less than 7 percent on zone III with moderate hazard and only less than 1 percent falls under zone IV, which is of high hazard.Research limitations/implications – The accuracy of the landslide hazard map needs to be assessed by cross‐correlation with landslide occurrence in the field.Practical implications – The map produced showed the potential application of GRASS as a tool for producing landslide hazard assessment map.Originality/value – The major outcome of this research is the possible use ...

Factors Controlling the Suspended Sediment Yield During Rainfall Events of Dry and Wet Weather Conditions in A Tropical Urban Catchment

The catchments of the Klang and Ampang Rivers are two sub-catchments that drain into the main Klang River, Selangor, Malaysia. Due to the development and siltation processes, the current capacity of the Klang River in the city centre is insufficient for accommodating the excess flood flow during major events, and, therefore overflows the riverbanks causing flash floods to occur in the Kuala Lumpur city centre. This study investigates the relationship between the rainfall, discharge and suspended sediment transport and its variations during the dry and wet periods in tropical sub-catchments; identifies the different hysteresis types of single flood events in the suspended sediment concentration/discharge relationships in the dry and wet periods, and determines the relationship between the types of single event hysteresis loops and the hydrological and sediment responses. Principal component analysis was performed to examine factors that have a major influence on the suspended sediment yields during both the dry and wet periods. The clockwise and counter-clockwise hysteresis loops occurring mostly during the dry period, can be described as events with moderate total rainfall, rainfall intensity (less than 10 mmh−1), average discharge and suspended sediment load. Counter-clockwise events occurring during the wet period are associated with low total rainfall, rainfall intensity, average discharge and suspended sediment load. The clockwise and counter-clockwise events that occurred in the wet period are related to events with a relatively high and low moisture condition, respectively. The figure-eight and complex hysteresis loop events occur predominantly during the wet period. The complex loop events occurred mostly during the wet period generates the highest suspended sediment load. The complex loop events occur mostly during the wet period generated the highest suspended sediment load.

A Preliminary Appraisal of the Effect of Pumping on Seawater Intrusion and Upconing in a Small Tropical Island Using 2D Resistivity Technique

The existing knowledge regarding seawater intrusion and particularly upconing, in which both problems are linked to pumping, entirely relies on theoretical assumptions. Therefore, in this paper, an attempt is made to capture the effects of pumping on seawater intrusion and upconing using 2D resistivity measurement. For this work, two positions, one perpendicular and the other parallel to the sea, were chosen as profile line for resistivity measurement in the coastal area near the pumping wells of Kapas Island, Malaysia. Subsequently, water was pumped out of two pumping wells simultaneously for about five straight hours. Then, immediately after the pumping stopped, resistivity measurements were taken along the two stationed profile lines. This was followed by additional measurements after four and eight hours. The results showed an upconing with low resistivity of about 1–10 Ωm just beneath the pumping well along the first profile line that was taken just after the pumping stopped. The resistivity image also shows an intrusion of saline water (water enriched with diluted salt) from the sea coming towards the pumping well with resistivity values ranging between 10 and 25 Ωm. The subsequent measurements show the recovery of freshwater in the aquifer and how the saline water is gradually diluted or pushed out of the aquifer. Similarly the line parallel to the sea (L2) reveals almost the same result as the first line. However, in the second and third measurements, there were some significant variations which were contrary to the expectation that the freshwater may completely flush out the saline water from the aquifer. These two time series lines show that as the areas with the lowest resistivity (1 Ωm) shrink with time, the low resistivity (10 Ωm) tends to take over almost the entire area implying that the freshwater-saltwater equilibrium zone has already been altered. These results have clearly enhanced our current understanding and add more scientific weight to the theoretical assumptions on the effects of pumping on seawater intrusion and upconing.

Quantification of Runoff as Influenced by Morphometric Characteristics in a Rural Complex Catchment

This study addresses the critical scientific question of assessing the relationship between morphometric features and the hydrological factors that increase the risk of flooding in Kelantan River basin, Malaysia. Two hypotheses were developed to achieve this aim, namely: the alternate hypothesis (runoff, is influenced by morphometric characteristics in the study watershed) and the null hypothesis (runoff is not influenced by morphometric characteristics). First, the watershed was delineated into four major catchments, namely: Galas, Pergau, Lebir, and Nenggiri. Next, quantitative morphometric characters such as linear aspects, areal aspects, and relief aspects were determined on each of these catchments. Furthermore, HEC–HMS and flood response analyses were employed to simulate the hydrological response of the catchments. From the results of morphometric analysis, profound spatial changes were observed between runoff features of Kelantan River and the morphometric characteristics. The length of overflow that was related to drainage density and constant channel maintenance was found to be 0.12 in Pergau, 0.04 in both Nenggiri and Lebir, and 0.03 in Galas. Drainage density as influenced by geology and vegetation density was found to be low in all the catchments (0.07–0.24). Results of hydrological response indicated that Lebir, Nenggiri, Galas, and Pergau recorded a flood response factor of 0.75, 0.63, 0.40, and 0.05, respectively. Therefore, Lebir and Nenggiri are more likely to be flooded during a rainstorm. There was no clear indication with regard to the catchment that emerged as the most prevailing in all the morphological features. Hence, the alternate hypothesis was affirmed. This study can be replicated in other catchments with different hydrologic setup.