With the intention to reduce the negative  effects of ongoing bed erosion, as well as to  improve several other river functions such as  protection against floods, provision of safe and  efficient navigation and ecology, a ‘pilot project  longitudinal training dams’ was initiated. The  training dams have recently been implemented  in the Waal between Tiel and Sind Andries. In  this project, river groynes have been  completely removed and replaced by dams  that lie parallel to the river bank. With help of  the longitudinal training dams, a two-channel  river system is created in which the river is  divided into a main and side channel. The  dams are placed in a continuous manner with  openings in between that are relatively small  compared to the dam length. At the beginning  and end of the dam an inlet and outlet region is  situated, as shown in Fig. 1.  The combination of inlet and openings  allows for water and sediment to be divided  between the main and the side channel. Both  inlet and openings are constructed with the  help of a porous rock-layer. The crest heights  can be altered by adding or removing stones.  This is expected to influence the amount of  water and sediment entering the side channel  and can therefore be used as a regulation tool.