In collaboration with SINTEF Energy Research this thesis was a part of a project to increase Atlantic salmon production in the river Nausta. The main goal of this thesis was to collect, systematize, analyse and prepare field data. Two hydraulic models, the two dimensional model River2D and the three dimensional hydraulic model SSIIM, were established for a 400 m reach just upstream of Naustdalsfossen in the lower part of the Nausta River. The models were calibrated with the use of verifying data of three different discharges. Furthermore the model was adapted for a low flow condition and a one-year-flood. Analysis and adjustments of various habitat improvements were carried out with the hydraulic model. Combinations of different adjustments such as adding larger rocks, velocity concentrators, rock thresholds, deeper pools in addition to other enhancements were tested on the reach of interest. The results were evaluated by SINTEF Energy research in co-operation with NINA (Norwegian Institute for Nature Research). Furthermore the results were analysed with the use of biological preferences from the literature and from expert opinions in order to find the most optimal habitat improvements.