The effects of floods in the last decade have been studied in two tributaries of the Tajo River in the Tertiary basin of Madrid (central Spain). Although the streams flow parallel to each other, one, the Jarama River, has a meandering pattern with gravel bedload, and the other, the Guadarrama, is braided with sandy bedload. In spite of their planform differences, the main effects of flooding on ... [Show full abstract] both rivers have been channel incision, widening and straightening, with meander cut-offs. Both rivers show similar recent behaviour, mainly because of the loss of discharge and bedload. The decrease in the discharge is related to dam construction and water pumping for irrigation, whereas the bedload has been reduced as a result of gravel mining, either directly from the channel bed, or from areas on the floodplain connected to the channel. These effects have been identified in aerial photographs from 1956 onwards, although it is since the 1970s that these processes have become acute. The study of historical maps and older aerial photographs reveals that some of the effects may have started even before 1956. Furthermore, the sedimentary record of the floodplain shows intense aggradatioa since the beginning of last century, indicating that channel incision is not just a recent anthropogenic effect but a natural tendency of the rivers, which may be related to long-term adjustment to changing climate conditions. After a significant period of alluviation and aggradation, the rivers are now going through a new entrenchment stage, with the anthropogenic activity enhancing the natural trend.