Managing construction risks with a large number of risks with small impact can increase the additional effort and cost of inefficient construction. Therefore the variables need to be eliminated. The aim of this study is ranking the risk variable based on its frequency of occurrence by integrating time, cost, and quality criteria simultaneously and selecting the top ten variables with the order of the most significant impact. The risk variable ranking based on triple project objective of cost, time, and quality simultaneously is a challenge for particular projects or regions contributing to the risk context. A number of 127 qualitative risk variables of 14 factors occurring in a project to be eliminated require a method/technique. A fuzzy TOPSIS method involving linguistics data is proposed to capture vague conditions. Results show that the top ten rankings of risk variables based on integrating the different weights of cost, time, and quality are successfully identified by concluding that the labour factor is the most dominant variable affecting project risk in context the rehabilitation and reconstruction posttsunami disaster, especially in Aceh-Indonesia. The variables are lack of labour, unskilled labour, undisciplined labour, and low productivity of labour. This condition can differ from different risk contexts. This research is different from other studies that only review cost, time, and quality separately. We stated that to integrate all three criteria of cost, time, and quality simultaneously is more logic to analyze risk variable ranking.
Sediments deposition derived from the erosion in upstream areas can lead to river siltation or canals downstream irrigation. According to the complexity of erosion problem at Keuliling reservoir, it is essential that topography, hydrology, soil type and land use to be analyzed comprehensively. Software used to analyze is AVSWAT 2000 (Arc View Soil and Water Assessment Tools-2000), one of the additional tool of ArcView program. The results obtained are the watershed delineation map, soil type map to produce soil erodibility factor (K) which indicates the resistance of soil particles toward exfoliation, land use map to produce crop management factor (C) and soil conservation and its management factors (P). Hydrology analysis includes soil type, land use and utility for the erosion rate analysis through Hydrologic Response Unit (HRU). The biggest HRU value of sub-basin is on area 5 and the lowest one is on area 10. All four HRU in sub-basin area 5 are potentially donating high value for HRU. In short, this area has the longest slope length so that it has a large LS factor. About 50% of the land was covered by bushes which gain higher C factor rather than forest. Moreover, it has contour crop conservation technique with 9-20 % declivity resulting in having dominant factor of P. Soil type is dominated by Meucampli Formation which has soil erodibility factor with high level of vulnerable toward the rainfall kinetic energy. All in all, the vast majority of HRU parameters in this sub-basin area obtain the highest HRU value. Hydrology analysis, soil type, and use-land are useful for land area analysis that is susceptible to erosion which was identified through Hydrologic Response Unit (HRU) using GIS. As the matter of fact, spatially studies constructed with GIS can facilitate the agency to determine critical areas which are needed to be aware or fully rehabilitated.
Abstract. One of the important factors in channel dimension is the Manning's coefficient (n).This coefficient is influenced not only by the channel roughness but also by the presence of plants in the channel. The aim of the study is to see the effect of the ratio between the height of the rigid plant and water depth on the Manning's coefficient (n) in open channel. The study was conducted in open channel with 15.5 m long, 0.5 m wide and 1.0 m high, in which at the center of the channel is planted with the rigid plants with a density of 42 plants/m 2 . The flow was run with a discharge of 0.013 m 3 /s at 6 ratios of H plants /H water , namely: 0; 0.2; 0.6; 0.8; 1,0 and 1,2, to obtain the velocity and water profiles. Then the value of n is analyzed using Manning's equation. The results showed that the mean velocity becomes decrease 17.81-34.01% as increase the ratio of H plants /H water . This results in increasing n value to become 1.22-1.52 times compared to the unplanted channel (n o =0.038). So, it can be concluded that the ratio between the rigid plant's height and water depth in the open channel can affect the value of Manning coefficient.
One of an important parameter to study water flow in channel is Manning’s coefficient (n). This coefficient is produced not only from material forming the channel, but also due to presence of vegetation in channel. The aim of research is to study the effect of vegetation density and height on Coefficient of Manning in open channel. The study was conducted in open channel with 15.5 m long, 0.5 m wide and 1.0 m high. At the center of 3 m long of channel is planted with Sweet flag (Acorus calamus). The impact of various densities and heights of sweet flag were examined using fixed discharge to measure velocity and slope energy. Coefficient of Manning was obtained using Manning’s equation. Statistical analysis of variance with significance level of 0.05 was adopted to evaluate the effect of variables. The result showed that increasing density and height of Sweet flag make decreasing velocity and increasing Coefficient of Manning to be 0,043-0,064, or 1.40-2.10 times compared to un-vegetated channel (no=0.031). Based on statistical analysis, it is found that Fcalc=15.646 and 16.928 for vegetation density and height respectively, which is larger than FStat=2,603. It can be concluded that density and height of vegetation significantly influence on Coefficient of Manning.
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