Profiles elevation vs. distance for the main river systems and their terraces. Grey: elevation in 10 km-large buffer (area within 10 km of the river) around the river trace (cf. Fig. 1). The topmost terraces are shown as color dots. The color code is a function of the unified sequence defined in the results part (cf. Fig. 5). The panels stand for: (A) the Ebro main stream, (B) the Segre and tributaries, (C) the Gállego valley and (D) the Aragón and Cidacos valleys. The x-axis is the distance to the Ebro mouth.