Master of Engineering in Environmental Water Resources Engineering and Managementhttp://dl.lib.uom.lk/handle/123/161222024-03-28T11:07:22Z2024-03-28T11:07:22ZAssessment o f the degree of public awareness on Tsunami Galle District , Sri LankaKumara, GGAhttp://dl.lib.uom.lk/handle/123/105182023-10-13T00:18:03Z2014-08-15T00:00:00ZAssessment o f the degree of public awareness on Tsunami Galle District , Sri Lanka
Kumara, GGA
Tsunami is one of the most devastated coastal hazard, which may perhaps yields serious damages to both human lives and properties in affected islands like Sri Lanka. As an island, Sri Lanka has also become a Tsunami prone risk zone as frequent earthquakes reported in Java Sumathra region. Knowledge and the awareness on such coastal hazards of the community is a vital facts, which results is minimizing its adverse effects. Developing awareness processess and effective communication systems will definitely assist in the designing of hazards maps and evacuation plans. 26th December 2004 Tsunami has hit the Sri Lankan coastal regions creating many lives losses and property damages as a result of lack of previous experience in similar typed hazard. and post second anniversary of 26th December 2004 Tsunami event. At the survey, 1200 sample was selected based on geographical representations of affected Grama Niladhari Divisions. School community and the general public are substantially encountered at the survey. A questionnaire was used to collect data from the sample and informal discussions were conducted to collect additional information. The survey was conducted by a team comprising of Engineers, Sociologist etc. The data collected was analyzed and results are presented in the report. Media effect, communication gaps, reliability of early warning systems, public responsiveness, suggested countermeasures are the critical outcomes of the study which needs to address at policy level.
2014-08-15T00:00:00ZUrban drainage network generation using geographical information systems - a case study of three catchments in Greater Colombo AreaAttygalla, Nhttp://dl.lib.uom.lk/handle/123/19722023-01-24T09:43:42Z0012-01-01T00:00:00ZUrban drainage network generation using geographical information systems - a case study of three catchments in Greater Colombo Area
Attygalla, N
Establishing proper drainage system has become a major challenge especially in the urban areas. Drainage systems consist of canal network and drainage structures such as culverts. Once the drainage system is established, it can be expanded to identify the discharge at the outlet of a watershed or in flood plains for a given precipitation. Therefore identification of drainage network is a primary requirement for drainage design. Drainage network identification through engineering survey is a time consuming and costly effort. Some of the engineering applications related to drainage network such as culvert design, flood plain analysis, do not need very high accuracy. The drainage network identification can be done using less time-consuming computer technology, if the generated accuracy is satisfactory for engineering applications. Therefore this research is concentrated on the aspects related streamline generation and accuracy assessment. The main objectives of this study are,
- Generation of streamline network
- Accuracy comparison of generated streamline
- Identifying the parameters affecting the accuracy
- Accuracy comparison of observed culvert location
The study is carried out in three watersheds in the Greater Colombo region. The Torrington watershed is selected as the primary watershed for the study and the watershed area is around 450 ha. The Attidiya and Katubedda watersheds areas are found as 190 ha and 250 ha respectively.
The study requires data in digital format. Digital data extraction is carried out in three processes. Part of digital data such as existing stream network is extracted from paper maps, through scanning and geo referencing. Also digital base map features of building, roads, contours and spot heights are extracted from the database of
National Water Supply & Drainage Board (NWSDB). Rest of the digital data such as culvert locations are extracted using Global Positioning System (GPS) technology.
Data processing and analysis component is carried out using the extracted digital source data. Streamlines are generated from DEM (Digital Elevation Model) by varying the resolution from 2m, 5m, 10m, 20m and 50m. While generating streamlines on GIS, it is necessary to provide a threshold value. This threshold value is selected in a way that the level of branching off of generated and extracted streamlines at the outlet of watershed are similar. Accuracy assessment is carried out with the newly established raster based accuracy assessment method. Other than that a reference box analysis is carried out to obtain a general impression of the possible streamline pattern comes under a particular Root Mean Square Error (RMSE) value range. Accuracy variation with the change of DEM resolution at particular location and the accuracy variation along the streamline with the watershed parameters such as stream order, stream slope, surface slope, building density and stream sinuosity are observed. It is found that stream order and surface slope has a relationship with streamline accuracy. In the same way culvert location accuracies are identified by varying the resolution.
Result and discussion sections focus on the key results of data processing and analysis. It is discussed that raster based accuracy assessment is more representative when compared with vector based methods. Once the accuracies are assessed, the average accuracy variation (RMSE) with respect to different watersheds is discussed. Also accuracy variation with the resolution and the accuracy variation along the streamline with the affecting factors of stream order and surface slope are discussed. The possible reasons for unexceptional variation of streamline from the expected patters are analyzed.
It is also discussed about establishing a representative per cell threshold value for urban watersheds. Once that is established it is possible to identify the threshold
value should be given for newly selected watersheds. Finally accuracy variations of culvert locations with respect to the resolution are also discussed in depth.
It was found that raster based accuracy assessment methodology is more realistic. Average Root Mean Square Error value (RMSE) of streamline is increased with the surface flatness of the watershed. Also in general RMSE value of generated streamline is reduced when cell size become finer. The per cell threshold value is determined as 0.016. It can be utilized to generate streamline network having same stream order of actual streamline at the outlet. It is shown that accuracy of generated streamline improves with the increment of stream order and surface slope. The deviation of observed culvert
0012-01-01T00:00:00ZEvaluation of operational performance in Rajangana major irrigation scheDe Alwis, SMDLKhttp://dl.lib.uom.lk/handle/123/7082022-10-12T03:26:22ZEvaluation of operational performance in Rajangana major irrigation sche
De Alwis, SMDLK
Managing the resources in a major irrigation scheme needs more attention on system performance to get the optimum production out of the available resources. In Sri Lanka, most of the major irrigation schemes are managed with conventional management strategies along with the traditional experiences gained by both farmers and officers. Some instances, systematic observation of resource use and management are not adhered by the scheme managers as well as by the farmers. This situation has effected to low productivity of the schemes. Providing adequate effort for integration of inter-related activities and combining the physical, biological and human factors on productivity is not so easy task in the irrigated agriculture sector. Therefore assessing the issues and constraints and evaluating the scheme performance in a systematic way enhance the managers to take prompt action when required while delivering the services in operational procedures./
In view of developing a suitable performance assessment programmed for a major irrigation scheme a study was done on performance assessment under water use efficiency, irrigation practices and land productivity in the LB Tract 01 area of Rajangana Irrigation Scheme. This study included turnout area basis assessment with the collection of data and information through literature review and field surveys along with the statistics collected from related institutions and departments. Study was carried out to evaluate the performances of Irrigation system through performance indicators by using systematic observations, documentation and interpretation methods. Several assumptions were made during the analysis with regards to data that were out of reach or inaccessible. Data and information used were from year 1990 Yale season to Year 2002 Yale season.
The Rajangana Major Irrigation Scheme is one of the Major Irrigation Schemes in dry zone of Sri Lanka and it is considered as a water abundant scheme following the restoration of Kalawewa under the system "H" of Mahaweli Development Program. Rajangana reservoir provides irrigation water to 5520 ha of lands under gravity irrigation system and 1602 ha of lands under the lift irrigation system. At present there are about 6275 ha of lands under gravity irrigation system and area under the lift irrigation system has reduced to 1050 ha mostly due to other constraints of lift irrigation system such as irrigable land being utilized for homestead purposes and abandoning of some lands as a result of inadequate operation and maintenance of pump houses. This scheme has been divided in to 25 tracts to provide irrigation facilities. Out of these 7 tracts belong to the LB irrigation system and 18 tracts belong to the RB irrigation system. It appears that the productivity of the scheme does not show a good performance in utilization of
water & land when compared with yield and income of the farmers and as a result the living standard of the settlers too does not indicate as satisfactory./
This study examined the cultivation patterns of past seasons, irrigation water use by the farmers, production cost, farmer incomes, cost of operation and cost of maintenance of the system. In this study the command area under the Tract 01 of LB system was selected as a pilot area because similar variations were observed in other tracts during preliminary surveys. Outputs of the study are expected to be generalized to whole scheme./
Performance of the irrigation system depends on a large number of variables. In this study 11 performance indicators assessed the system performance in four main areas via, service delivery, agriculture production, agriculture economics & financing an system sustenance. Spatial and temporal variation of water deliveries were found ire terms of adequacy and irrigation duty. Water use efficiency measured in terms old grain mass per unit volume of water reflects that the water use efficiency of the study area is far below the established benchmark value of 0.372Kg/m3. Stud)M revealed that the irrigation system of the study area is subjected to deterioration due to inadequate attention on operation and maintenance. The efficiency of getting potential yield in the area is 68% with medium level productivity performance.
Recommendations of this study would be useful to managers who deal with major irrigation system management in planning the cultivation seasons by optimizing the productivity of land and water.
A Thesis submitted to the Department of Civil Engineering for the Degree of Master of Eng. in Environmental Water Resources Eng. and Management
The Estimation of probable maximum precipitation for Sri LankaFernando, WCDKhttp://dl.lib.uom.lk/handle/123/6952023-10-13T01:53:24ZThe Estimation of probable maximum precipitation for Sri Lanka
Fernando, WCDK
On 24 and 25lh of December 1957 heavy rain fell in the North Central Province; 206.5mm and 219.7mm of rainfall were recorded at Anuradhapura meteorological station and were nearly twice that recorded during the previous high floods. Some of the major tanks such as Kalawewa, Nachchaduwa and Huruluwewa in Anuradhapura breached, resulting in catastrophic damage to infrastructure. The storm of 392.5 mm on 8,h June 1996 over Ratnapura resulted in a disastrous flood which caused enormous damage and rendered many people homeless.
The design of a hydraulic structure often requires an estimate of the design flood which has considerable uncertainty about its magnitude. However it should be determined in relation to the project feature for which it is required. When 100% virtual security against failure is required, then the design criteria should be based on the Probable Maximum Flood, which in turn requires the estimation of Probable Maximum Precipitation (PMP).
The research compares the results of 24-hour PMP obtained by two methods. One is based on storm maximization or a hydro-meteorological method and the other uses the statistical method developed by Hirschfield. In this study, the last 105 years (1896-2000) of daily rainfall data from the meteorological stations at Anuradhapura and Ratnapura have been analyzed.
The 24-hour point PMP for Anuradhapura showed that the results were in the range of 600-625mm based on the statistical method while storm maximization yields a PMP of 425mm with the adjustments of moisture and wind maximization. On the other hand the statistical result for Ratnapura was in the order of 990 to 1120mm and the PMP calculated by storm maximization was 1025mm. If storm maximization was based on true rainfall, PMP values were increased up to 623mm and 1058mm for Anuradhapura and Ratnapura respectively.
Finally suggestions have been made to improve the effectiveness of the different approaches, in estimating PMP.
MEng. in Environmental Water Resources Engineering and Management