Introduction
A least-cost pipeline path simulation was performed on the two selected reservoir sites to selected targeted demand areas in the Langkawi Island, Malaysia. The selected reservoir sites were Ulu Melaka and Limbong (Wan Yusof and Baban 2000). In the development planning, future water supply requirement in the Langkawi Island will be targeted to major towns of Kuah and Temoyong. In this study, the work concentrated on finding the least-cost path to a major town (Kuah) and a new tourist area (Temoyong)
Physical factors and landuse/cover types
The least-cost pipeline routes to the two targeted areas (Kuah town and Temoyong resort areas) in the Langkawi Island can be influenced by land use, terrain, geological and environmental factors (Jankowski, 1995). Changes to these factors may incur higher cost such as trenching in consolidated rock, clearing of trees and shrubs, crossing of rivers or railways may require the building of bridges or supports to cross or pass through agricultural land (Feldman et. al., 1996). Based on these facts, an analysis of the relationship between physical factors and land use/cover types for the whole of the Langkawi Island was performed (Table 1). Table 1 shows that land use/cover types under considerations were inland forest, rubber, mangrove, mixed horticulture, paddy and grassland. Information regarding their physical factors such as height, slope and geology and the percentage coverage for each factor were extracted from the digitised maps available for the Island. Using EXTRACT from the IDRISI function, a summary of data values for each class was extracted.
Table 1 also shows that about 88% of inland forest was within the highlands with altitudes between 20 and 400 m, slope of greater than 20o and over 90% are on rock material foundations. Pipeline construction on highlands with rock materials such as granite, mudstone and limestone is difficult and in some cases blasting may be required, which will increase the cost (Feldman et. al., 1996). On the contrary, construction on lower plains (between 0 and 30m) with gentle slopes of 0-2o, and the presence of alluvial material on paddy and grass will give easier access for the construction plants to manoeuvre and makes trenches. Mangrove areas are considered as an environmentally sensitive area (Feldman et. al., 1996), so the possibility of pipelines crossing in this area could arouse conflict with environmentalist groups and therefore it was not considered to be viable.
Table 1 The analysis of the physical factors against the land use/cover types
for the whole of the Langkawi Island.
| Land use/cover |
Height (m) |
% of range |
Slope (degrees) |
% of slope |
Geology |
% of geology |
| Inland forest |
20-400 |
88 |
0-40 |
81 |
Granite, mudstone and limestone |
97 |
| Rubber |
11-70 |
84 |
0-8 |
80 |
Granite and mudstone;Alluvium |
6722 |
| Mangrove |
0-20 |
80 |
0-2 |
83 |
Alluvium;Limestone |
5933 |
| Mixed horticulture |
1-30 |
80 |
0-5 |
91 |
Alluvium;Granite and mudstone |
5337 |
| Paddy |
1-30 |
85 |
0-2 |
88 |
Alluvium;Granite and mudstone |
5840 |
| Grass |
0-20 |
82 |
0-2 |
92 |
Alluvium;Granite |
6818 |
The results of this analysis were used as the basis for determining a friction surface factor for the least-cost pipeline routes. The level of difficulty in crossing each land use/cover types under the influence of their physical factors determines the friction surface cost-value. For example, high relief terrain increases the cost of pipeline engineering and construction, and an unconsolidated fine-grained soil material is preferred to a rock surface because it does not require blasting (Janskowski and Richard, 1994; Janskowski, 1995; Feldman et. al., 1996).