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Assessment of the potential amount of floating debris in Lule river
2008 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This project deals with the possible amount of floating debris as a result of landslide activity along the Lule river. Some kinds of debris can be considered harmless while others may be harmful to the dam by clogging the spillways, depending on their size and density. In any case different forms of floating debris have different impacts, which is why both, amount and distribution of characteristics, are to be determined in this study. Using all the input data described in chapter 2 a basic impression about the slope stability situation in the working area was gained. Those locations, well known already at that point, gave a comparatively good estimation of the slope stability in these limited areas, but in order to get a slope stability assessment over the entire working area it was necessary to find correlations between slopes and apply characteristics known for some locations onto slopes with similar features in terms of geometry, material or vegetation. The field investigations performed during that stage offered opportunities to collect data not only for these tasks, but also about the vegetation characteristics of the working area. Four vegetation classes were defined during the field work. Already during that stage the number of dams that might become confronted with significant amounts of floating debris was narrowed down to only three, namely Vittjärv, Laxede and Porsi. With the help of the data collected during the fieldwork all potentially hazardous locations were classified in terms of extensions, geometrical characteristics and vegetation. Based on the findings during the field investigations the total potentially unstable surface area was calculated to a value of 326605 m². A value which was slightly corrected later on to 324585 m², after the SlopeW calculations indicated that not always the entire slope has to be considered unstable and that the land surface right behind the crest of a slope might have to be considered unstable terrain as well. Calculations using the SlopeW software were performed mainly in order to find conditions under which slopes can be considered stable or unstable considering water levels in a 10.000 year flood event. Out of the 28 locations identified during the fieldwork as much as 25 were considered potentially unstable. Finally the information concerning extent and vegetation class of these 25 locations was combined in order to compute values for the total amount of trees over the entire unstable surface area, which resembles the amount of floating debris. The total amount of trees, as it can be observed in appendix III, was highest for the Porsi dam (46699 logs) followed by Vittjärv (23257) and finally Laxede (14021). On the first impression the results might suggest that Porsi should require most attention in terms of precautions to spillway clogging. In fact, however, other factors like the water level variation or the size distribution of the floating debris have to be considered before measures can be taken. Nevertheless the results deliver a base for dam safety engineers to assess the threat to the dams along Lule river.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Dams, dam safety, floating debris, slope stability, vegetation characteristics, Lule river
Keyword [sv]
URN: urn:nbn:se:ltu:diva-43908ISRN: LTU-PB-EX--08/072--SELocal ID: 1ba18ece-9c7d-4630-a7ef-7fdecfd89657OAI: diva2:1017150
Subject / course
Student thesis, at least 30 credits
Educational program
Civil Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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