The investigations carried out in the estuary part of the Raba river focused on straight sand dunes shaping the river bottom. The following characteristics of the dunes were considered: height (H) measured at the highest rise of the crest, length (L) measured parallel to the flow, width (W) measured perpendicular to the length, and angle of the lee- -side and stoss-side slopes. Field studies included also the measurement of the depth of water (h) above the characteristic points of the bed forms. Using the data obtained, indexes characterising the shape (L : H, W : L) and the steepness (H : L) of dunes were calculated, and formulae describing the functional dependence of height and steepness, respectively, on length were developed. The geometrical parameters, i.e. length and height, of the forms were also related to the water depth.

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