Roberto S. Clemente

Assessment of wetland ecosystem health in Lower Songkhram, Thailand

A study was conducted to assess the ecosystem health of Lower Songkhram wetland in Thailand, using a newly developed wetland ecosystem health index (WEHI) based on analysis of field survey and secondary data of the most dominant physical, environmental and socio-economic factors extracted by principal components analysis (PCA). The most influential physical, environmental and socio-economic factors identified were rainfall and awareness and participation of the local community, which had positive effects, whereas soil electrical conductivity (EC), biochemical oxygen demand (BOD) and urban development had negative effects. Based on the results, 9 of the 40 land units of the study area were in very good or good health, 11 in reasonable health, while 20 were found to be in poor or even very poor condition. These findings will be useful for decision-makers in planning and executing an effective and holistic strategy to prevent further wetland degradation.

Flood risk assessment in the region surrounding the Bangkok Suvarnabhumi Airport

Flood hazard, vulnerability, and risk assessments were conducted in the area surrounding the new Bangkok International Airport. A hydrodynamic model was used to simulate the flood flow through the study area. Results show different levels of flood hazard for risk zones for 25-, 50- and 100-year return periods of rainfall.

River basin water quality assessment and management: case study of Tha Chin River Basin, Thailand

The water quality improvement plan for the Tha Chin river basin in central Thailand has been studied by using integrated land-use and water quality modelling. There has been little research on water quality planning in this basin due to the complex and intensive data requirements and also due to modelling difficulties. This research attempts to apply the integrated land-use and water quality modelling to the Tha Chin river basin. Loading reduction scenarios were applied to find out the appropriate loading reduction target and hence the improved water quality in the main stream.

Evaluation of water use sustainability under future climate and irrigation management scenarios in Citarum River Basin, Indonesia

Sustainable water use in agriculture faces several challenges due to future climate change, increasing population, and higher living standards. Adapting to possible future changes in climate and sustaining the use of water are some of the challenges that face future agricultural water management. In this research, the sustainability of irrigation water use was assessed by performance criteria that consider the effects of climate change and adaption management on irrigation. The model, built using the Water Evaluation and Planning (WEAP) system, is calibrated using the stream flow and the requirement of water for irrigation. The model was used to examine two future climate projections (A2 and B2), for time periods until 2099, and for four scenarios: (1) an increase in the irrigated area, (2) an increase in crop intensity, (3) a change in the crop pattern, and (4) a combination of increased irrigation area and increased crop intensity. Results show water supply is projected to increase by about 85 and 60% (relative to the historical period) in A2 and B2 climate scenarios, respectively, by the end of the century. The requirement for irrigation water will decrease in the future, relative to the historical period. The sustainability index will also decrease in the future, relative to the historical period. Relative to the baseline scenario, increasing the irrigated area is more sustainable than increasing the crop intensity or combining increased crop intensity with increased area under irrigation. Increasing the irrigated area is more amenable to adaption to possible future climate changes.

Assessment of Different Irrigation Management Models in Vietnam

An assessment of three institutional models for irrigation management in Vietnam is presented. The first model is a joint management by a state agency and farmer organization; the second is a shared management by a quasi-state and farmer organization; and the third is management solely by a farmer organization. The first model is a conventional management system, whereas the latter two models have recently been introduced in a limited number of projects as a result of the government policy on reform in the irrigation sector. Three study sites are identified to represent three management models. Apart from the institutional framework and selected management functions, water distribution and agricultural productivity are evaluated and compared. Results indicate the better performance of management models with increased involvement of farmers in the decision-making process. It is recommended that the hydraulic boundaries should be taken into consideration in reforming management systems for irrigation projects.

EQUILIBRIUM OF CRENULATED BAYS IN THAILAND

The C coefficients in the now well-known parabolic bay shape equation (PBSE) are the most important parameters for verifying the bay beach stability or designing a headland bay beach in static equilibrium. These coefficients are revised specifically for bays in static and dynamic conditions in Thailand. Three techniques, namely Least Square (LS), Genetic Algorithms (GA), and Differential Evolution (DE) are used to determine the alternative coefficients. The newly derived C coefficients for static equilibrium bays (SEB) differ slightly from the original coefficients. Dynamic equilibrium bays (DEBs) with sediment within the embayment are analyzed to obtain a new set of C coefficients, which are a function not only of wave obliquity but also sediment supply ratio (SSR), which is a new parameter representing the ratio between the rate of sediment supplied from a river source to the bay and the longshore sediment transport rate. The resulting new C coefficients for DEBs vary uniformly and systematically, similar to those for the SEBs, and are expected to be applicable to DEBs elsewhere for coastal management.

Finding appropriate interpolation techniques for topographic surface generation for mudslide risk zonation

Mudslides and debris flows are now more common problems in tropical regions than landslides. This article addresses the issue of modelling mudslide-susceptible locations using an information value approach. Landsat 7 (ETM+) was employed to create a land-use map with limited field checks. Other parameters considered were lineament, road, soil, stream network and lithology. Topographic parameters such as slope and aspect play a dominant role in slope stability studies. Maps for slope and aspects were developed from a digital elevation model using statistical surface interpolation techniques. This article offers insight into the importance of the selection of suitable surface interpolation techniques. The three surface interpolation techniques evaluated in the study were: inverse distance weighted, Kriging and Spline. These were found to have varied accuracies of interpolation surfaces for all parameters, including elevation, slope and aspect. Surfaces offering the best accuracy were adopted for the information value approach for mudslide susceptibility zonation.