Engineer : Journal of the Institution of Engineers, Sri Lanka
[0 followers] Follow
Open Access journal
ISSN (Print) 1800-1122
Published by Sri Lanka Journals Online [47 journals]
- From the Editor Vol. 44(3)
Abstract: No abstract available Published on 2016-05-05 00:00:00
- Identification of the Spatial Variability of Runoff Coefficients of Three
Wet Zone Watersheds of Sri Lanka
Abstract: Runoff estimation from rainfall records in the absence of stream gauge records is essential in Sri Lanka, because most of the watersheds are ungauged. Since runoff depends on the catchment characteristics in addition to the rainfall, this study focuses on streamflow determination as a function of land use, soil and slope from developed GIS model. This study developed a method to estimate runoff coefficient as a function of land use, soil and slope within the wet zone basins of Sri Lanka.Three Wet Zone basins, Kalu Ganga, Kelani Ganga and Attanagalu Oya were selected for the study. Regression analysis showed that the computed runoff agreed with the observed runoff with R2 values of 0.80, 0.78 and 0.83 for Kalu Ganga, Kelani Ganga and Attanagalu Oya basin respectively. Averaged runoff coefficients, for basins with the spatial variation were calculated as 0.52, 0.49 and 0.51 for Kelani Ganga, Kalu Ganga and Attanagalu Oya sub basin respectively. Study revealed that credible runoff coefficient will not be represented simply by the ratio between runoff and rainfall where runoff depends highly on catchment characteristics.
Published on 2016-05-05 00:00:00
- Preparation of the Stormwater Drainage Management Plan for Matara
Abstract: Matara Municipal Council area had been experiencing stormwater drainage problems causing inconvenience to public, interruption to work and damage to property. Though the Matara Municipal Council (MMC) had carried out a project in 2001 to develop its drainage canals, there were many cases of flooding within its boundary limits. In order to achieve a suitable plan for stormwater drainage management, the present work carried out an analysis of the associated stormwater drainage system. Systematic field data collection activities were done to identify the flood problem of the area, and to capture sufficient details of terrain and drainages. GPS surveys were conducted to identify the road and drainage alignments. A main feature of the study was the conduct of a road drainage survey which among many other details captured drainage directions along and across the roads. This survey helped to rationally identify the undulations in the terrain to generate the digital terrain model for the generation of stream network and delineation of watersheds. The 1:10,000 elevation data supported by the field work information showed the capability to generate a representative topography for stormwater drainage assessments. Analysis also used a simple Geographic Information System to prioritize critical flood affected areas and enabled identification of critical watersheds for engineering interventions. The present canal system was evaluated with that generated by the model and several sections were identified for early drainage designs these locations were verified in the field. Present work identified that in the MMC area 42% of roads coincide with the stream network indicating a loading of street stormwater drains with runoff generation as a result of terrain changes affected at individual compounds. 164 identified flood locations were analysed with drainage directions and surrounding elevations supported by detailed engineering inspections at specific locations to provide short term solutions. The study made recommendations with respect to development plan approval procedures, preparation of a suitable stormwater drainage database and the need of guidelines for developers to mitigate stormwater drainage problems as part of the long term solutions.
Published on 2016-05-05 00:00:00
- Impact on Existing Transport Systems by Generated Traffic due to New
Abstract: Impact of future traffic generated due to a development activity was forecasted on available information at the time, for a proposed building complex in Colombo taking it as a study sample. Through this study a complete pre-assessment of ‘in-coming’ and ‘out-going’ vehicles which generates due to the proposed development was conducted before hand, and observed how it would affect the surrounding road network in future. Then it was also observed that, whether the impact was within, or outside the tolerable limits.Once the proposed development was completed, and after few years of its operation, a validation was carried-out to assess the findings of the initial study which was conducted at the proposal stage of the development. The validation study results confirmed that the traffic generated due to the development was within tolerable limits of the surrounding road network as indicated in the initial study; hence the initial predictions were valid. Study also highlights the importance of development of local norms for traffic generating factors for different types of developments.
Published on 2016-05-05 00:00:00
- Comparison of Performance Assessment Indicators for Evaluation of
Irrigation Scheme Performances in Sri Lanka
Abstract: Managing resources in a major irrigation scheme needs more attention on system performance in order to get optimum production out of available resources. In Sri Lanka most major irrigation schemes are managed using conventional management strategies together with the traditional experiences of farmers and managers. In most instances a systematic approach for observation or resource use and management are not adhered to either by scheme managers or by farmers. It is often observed that this results in low productivity. As such there is a need to evaluate irrigation scheme performance using suitable performance indicators in order to identify shortcomings and to find out solutions for increasing the productivity of such schemes. Since there are many factors affecting productivity of an irrigation scheme, most relevant factors should be identified in order to ascertain the most relevant data, minimum time, money, and expert services are spent. It is commonly believed that the present way of data collection by the majority for scheme evaluations do not serve the purpose since they are not designed for Sri Lanka’s national needs. The present work is towards the development of a suitable performance assessment program for irrigation schemes in Sri Lanka considering water use efficiency, irrigation practices and land productivity. A critical comparison and review of available indicators were done considering the adequacy to monitor service delivery, productivity and agricultural economics and financing on irrigation system sustainability. One new indicator for water service delivery reflecting the effect of actual rainfall received was identified in this study along with two new indicators as Government Involvement and Beneficiary Involvement. This is proposed to monitor system sustenance which is a very important issue in the light of recent state policy of handing over of irrigation schemes to farmers. The present work after a systematic evaluation identified eleven suitable indicators for system performance measurement that would require minimum efforts on additional data collection and mobilising of fresh resources. Published on 2016-05-05 00:00:00
- Pull-out Behavior of Reinforcing tendons of Nehemiah Anchored Earth System
Abstract: The Nehemiah anchored earth wall system is a type of mechanically stabilized backfill structure where the mode of stress transfer from the backfill to the reinforcement is by passive resistance in addition to the friction. This paper presents the findings of pull out resistance of the reinforcing tendon together with the anchor block of the anchored earth wall system. Nine experimental tests were carried out to demonstrate the factor of safety of the pull out resistance of the anchored earth wall. In addition, a summarized historical background, design concepts, construction procedures and performance of the Nehemiah anchored earth wall system is provided. Published on 2016-05-05 00:00:00
- Economic Analysis of Water Infrastructure: Have We Got It Right'
Abstract: The paper describes shortcomings of the general economic analysis procedure adopted in water infrastructure development projects in Sri Lanka. As a case study an application of the ‘Educated Trade-off’ framework in the Ma Oya river basin is used to illustrate the shortcomings of general economic analysis procedure. This framework facilitates the systematic identification of resource uses and the possible range of environmental and social impacts by the water infrastructure project, through the involvement (consultation and participation) of key stakeholders. The study revealed two types of shortcomings that result in erroneous economic indicators: first, the lack of a competent process to establish the baseline situation leading to non-inclusion of some important social and environmental impacts, both positive and negative, by the project and, second, deviations from reasonable practices either due to negligence or on purposes that give decision makers optimistic data which could result in questionable decisions.
Published on 2016-05-05 00:00:00
- Application of WRF weather model to forecast precipitation in Nilwala
Abstract: The Weather Research and Forecasting (WRF) model is a numerical weather prediction and atmospheric simulation system designed for both research and operational applications. It was fine tuned to forecast precipitation over Nilwala river basin in Sri Lanka by investigating the impacts of its physics options on precipitation forecasting. In model fine tuning, impacts of microphyics schemes, cumulus schemes, land surface schemes, boundary layer schemes and long/shortwave schemes were investigated. Model predictions were compared with observed point rainfall data for three rainfall events to find reasonably good physics combinations. It was seen that the model combination, Ferrier microphysics scheme, Kain-Fritsch cumulus scheme, Rapid Update Curve land surface scheme, Yonsei boundary layer scheme, Rapid Radiative Transfer model longwave radiation scheme and Dudhia shortwave scheme yields good precipitation predictions over the basin when compared with the other physics combinations tested.
Published on 2016-05-04 00:00:00
- Future Impact on Maharagama Town Traffic Flow and Pedestrian Safety due to
Southern Expressway and Outer Circular Highway: Proposed Solutions
Abstract: Maharagama town becomes severely congested due to traffic & pedestrian activities during daytime. The absence of proper road shoulders makes the pedestrians enter the carriageway, which in turn creates a safety hazard and results in slowing down vehicular traffic. After the completion of the Southern Expressway and Outer Circular Highway, it is expected that additional traffic volume in Maharagama town area will result in traffic congestion and safety situation even worse. In order to find a solution for this situation, capacities of roads were evaluated by compiling data of vehicular flow, pedestrian movements and other supportive information of that area for present condition and for year 2030 (i.e. 20 years from now) with do nothing option.According to the obtained field data, and capacity calculations, all the roads in this area will badly fail to cater to the future traffic demand (i.e. for year 2030) unless some drastic improvements are conducted immediately. Also it was found that even at present, available pedestrian facilities were not satisfactory in this area, and the rate of accidents were high. Hence road widths, number of lanes, walkway shoulders, and pedestrian crossings were designed using the US highway capacity manual to evaluate the above conditions in the zone. Also geometric designs for islands were conducted based on AUSTROADS guides and templates. Objective of this study is to introduce suitable layout plan for Maharagama town area with required road improvements, road signs, and pedestrian facilities to enhance traffic flow and pedestrian safety for future operational conditions with the Southern Expressway and Outer Circular Highway in operation. Published on 2016-05-04 00:00:00
- Investigation of Two-Dimensional Interaction between Piles due to Pile
Abstract: Pile driving displaces adjacent piles out of their position. This effect is simulated numerically in this work by using the finite element analysis package PLAXIS. For simplicity, the analysis is done under plane strain conditions and linear elastic material behaviour, which in fact converts the pile into infinitely long walls. Pile driving is modeled by progressive expansion of a cavity. The smear zone is modeled around the pile using material of lower stiffness to take into account the compression of soil around the pile. A parametric study is carried out to investigate the predicted lateral displacement of the head of a pile due to driving of an adjacent pile, by varying the stiffness of the soil and spacing between piles.
Published on 2016-05-04 00:00:00