Alias Mohd Sood

SWAT-based hydrological modelling of tropical land-use scenarios

Abstract The Hulu Langat basin, a strategic watershed in Malaysia, has in recent decades been exposed to extensive changes in land-use and consequently hydrological conditions. In this work, the impact of Land Use and Cover Change (LUCC) on hydrological conditions (water discharge and sediment load) of the basin were investigated using the Soil and Water Assessment Tool (SWAT). Four land-use scenarios were defined for land-use change impact analysis, i.e. past, present (baseline), future and water conservation planning. The land-use maps, dated 1984, 1990, 1997 and 2002, were defined as the past scenarios for LUCC impact analysis. The present scenario was defined based on the 2006 land-use map. The 2020 land-use map was simulated using a cellular automata-Markov model and defined as the future scenario. Water conservation scenarios were produced based on guidelines published by Malaysia’s Department of Town and Country Planning and Department of Environment. Model calibration and uncertainty analysis was performed using the Sequential Uncertainty Fitting (SUFI-2) algorithm. The model robustness for water discharge simulation for the period 1997–2008 was good. However, due to uncertainties, mainly resulting from intense urban development in the basin, its robustness for sediment load simulation was only acceptable for the calibration period 1997–2004. The optimized model was run using different land-use maps over the periods 1997–2008 and 1997–2004 for water discharge and sediment load estimation, respectively. In comparison to the baseline scenario, SWAT simulation using the past and conservative scenarios showed significant reduction in monthly direct runoff and monthly sediment load, while SWAT simulation based on the future scenario showed significant increase in monthly direct runoff, monthly sediment load and groundwater recharge. Editor D. Koutsoyiannis; Associate editor C. Perrin

Trend analysis of water discharge and sediment load during the past three decades of development in the Langat basin, Malaysia

Abstract In this study, the trends of water discharge and sediment load from three hydrometric stations over the past 25 years of development in the state of Selangor, Peninsular Malaysia, were analysed using the Mann-Kendall and Pettitt tests. Landscape metrics for establishing the relationship between land-use changes and trends of hydrological time series were calculated. The hydrological trends were also studied in terms of rainfall variations and manmade features. The results indicate upward trends in water discharge in the Hulu Langat sub-basin and in sediment load in the Semenyih sub-basin. These increasing trends were mainly caused by rapid changes in land use. Upward trends of hydrological series in the Hulu Langat sub-basin matched its rainfall pattern. In the Lui sub-basin, however, trends of hydrological series, and variations in rainfall and land use were not statistically significant. Editor Z.W. Kundzewicz; Associate editor K. Hamed Citation Memarian, H., Balasundram, S.K., Talib, J.B., Sood, A.M., and Abbaspour, K.C., 2012. Trend analysis of water discharge and sediment load during the past three decades of development in the Langat basin, Malaysia. Hydrological Sciences Journal, 57 (6), 1207–1222.

A GIS-based model to analyze the spatial and temporal development of oil palm land use in Kuala Langat district, Malaysia

In Malaysia, areas under oil palm plantations have increased dramatically since the early twentieth century and have resulted in multiple conversions of land change. This paper presents a spatial and temporal model for simulation of oil palm expansion in the Kuala Langat district, Malaysia. The model is an integration of cellular automata (CA), multi-criteria evaluation (MCE), and Markov chain (MC) analysis while MCE provides transition rules of CA iterations and MC analysis assigns a transition probability to each single pixel at the time steps. Evaluation criteria consist of constraints and nine suitability factors indicating environmental and socio-economic issues of oil palm development. In the first simulation, changes of six land-cover classes were projected to the year 2008 based on transitions between 1997 and 2002. Two measures of quantity disagreement and allocation disagreement were adopted to validate model outcome. The simulation of land-cover change of the year 2020 was done based on the transition observed between 1997 and 2002 regarding the satisfactory agreement of the projection and the reference data at the first simulation. The results, based on five landscape metrics, indicated continuous spatial patterns of oil palm plantations but more fragmented spatial patterns of other land classes by the year 2020.

Lessons and challenges in land change modeling derived from synthesis of cross-case comparisons

This chapter presents the lessons and challenges in land change modeling that emerged from years of reflection and numerous panel discussions at scientific conferences concerning a collaborative cross-case comparison in which the authors have participated. We summarize the lessons as nine challenges grouped under three themes: mapping, modeling, and learning. The mapping challenges are: to prepare data appropriately, to select relevant resolutions, and to differentiate types of land change. The modeling challenges are: to separate calibration from validation, to predict small amounts of change, and to interpret the influence of quantity error. The learning challenges are: to use appropriate map comparison measurements, to learn about land change processes, and to collaborate openly. To quantify the pattern validation of predictions of change, we recommend that modelers report as a percentage of the spatial extent the following measurements: misses, hits, wrong hits and false alarms. The chapter explains why the lessons and challenges are essential for the future research agenda concerning land change modeling.

Assessing success of forest selective management system using geospatial technology

Since 1960s, forestry activities in Malaysia have been pushed towards steeper and erosive hilly areas which comprised of less big trees and less seedlings requiring a more precautious management practice in achieving forest sustainability. Hence in 1978, the Selective Management System (SMS) concept was adopted, planned for 25 years harvest cycle ensuring the next harvest with per hectare minimal 32 trees of above 30-45 cm diameter, producing minimal output of 40-50m3/ha, enriched with more Dipterocarp species. SMS conducted activities of pre and post felling inventories, flexible tree cutting limits and post felling treatment. However, after more than 30 years the success of SMS has not been fully determined though many visual observations inferred reduced merchantable stand and higher damaged of the residual forest. Consequently, this project intent to assess the success of SMS using geospatial technology. In this project, five forest parameters as SMS success indicators were measured; (a) forest density – estimated from Sentinel satellite image (10 x 10m) and GLAMA-GAP apps (b) tree number – enumerated at site plots (c) tree volume – determined by site plots measurement (d) tree composition – determined at site plots and (e) harvesting cycle duration – determined by historical data observation. Based on site measurement, it was found that all the plots have more than 32 trees/ha of above 30-45 cm diameter, comprising tree volume more than 40m3/ha and Dipterocarp species were 75% more than non-Dipterocarp. Meanwhile, NDVI from Sentinel 2 satellite image revealed that the density of the logged forest were more than 80% and subsequently confirmed 100% accurate by GLAMA-GAP apps. Results acquired concluded that in these project areas, SMS proved to be successful by complying all the requirement of SMS residual forest characteristic.