The aim of this thesis has been to study and analyse in detail the process by which timber floating in tributaries was phased out. The region covered is that of the Ume and Vindel rivers and the period studied is 1945-70. The years I945-60 have been the most central to the analysis. The approach taken was to study timber floating itself rather than the new transport alternative (lorries) which developed during the post-war period. This brought the increasing costs of timber floating in tributaries into the forefront of the investigation, along with the efforts made to restrain these by means of investment in and partial closure of the floatway network. The consequences in terms of changed labour demand are also discussed. An important part of the analysis has been to examine the inherent weaknesses of timber floating in tributaries and the internal driving forces underlying its phasing-out. The term "internal driving forces" connotes those forces which affected timber floating as a means of transport by causing its costs to rise. In other words it has not been a matter of looking at the direct competition from lorry transport and the advantages of the new transport technique but rather of identifying the drawbacks of floating, when, where and how they arose, and how they helped to make it relatively dearer, thus motivating the changeover to lorry transport. The internal driving forces were forest structure and labour costs. When labour costs incurred in timber floating in tributaries were rising rapidly and the dimensions of the logs became smaller in size, floating became a dearer transport solution than before. As regards changes in forest structure, the dimensions of logs were diminishing throughout the floating epoch. This meant that the risk of sinking during floating increased. The effect of this was that the need to bark the timber was increasing all the time, which in turn entailed an indirect transport cost for floating. In addition to this, smaller log dimensions affected the labour time and cost of floating. The changed labour conditions along with the changed forest structure showed the importance of studying structural change in the Norrland forest region. For during the later 1940s and early 1950s a shortage of labour presented itself, and the cause was to be found in the new job opportunities which were emerging, some in the rural areas, for example in the construction of hydro-electric powerplants, and some in the larger populated localities, and these factors taken together made recruitment for jobs in forestry and timber floating more difficult. One of the chief characteristics of the way events were moving was that recruitment shifted away from having mainly targeted the agrarian lower class of smallholders, crofters and leaseholders so that it now focused increasingly on freehold farmers while at the same time the recruitment base, having previously consisted of younger workers, was now composed mainly of older people. Also in this study, various factors have been examined which could conceivably explain the changes in productivity of timber floating in tributaries. The results show, for example, that during the 1950s a partial phasing-out had very small direct effects on productivity in the area studied. Thus the combination of investment and changes in the quantity of timber is the factor which best explains the differences between different tributaries in the trend of productivity. A tributary´s greater capacity to float timber did not necessarily signify a bigger labour requirement since to a certain extent the watercourse itself “did the job”. As regards investment, clearance operations using caterpillar tractors were probably very important. It is true that the genuine dependence of log driving in tributaries on nature influenced conditions varied strongly from year to year, but since the link between investment costs and the trend of productivity is significant, it still seems reasonable to draw the conclusion that investment lent impetus to the rise in productivity during the 1950s. / digitalisering@umu