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Training is the technique of confining or realigning a river to a straight and more regular course than that which occurs in nature (Fig. 15.14). In order to ensure long term stability, the banks usually have to be protected or artificially armoured. A realignment usually presents a problem regarding the bed slope, since the requisite change in level now has to take place over a shorter river length. The river will to some extent readjust itself in response to the training scheme. By protecting the banks, the number of degrees of freedom has been reduced, so the adjustment process will mainly affect the slope and the depth. The shortening of the channel path often results in erosion upstream and deposition downstream, as the channel seeks to restore its natural slope. If the engineer wishes to maintain the steeper slope, it may be necessary to armour the bed artificially. Armouring often consists of the dumping of stones, though on the outer banks short groynes, plastic sheeting or sheet piling may be installed. The engineer may use regime or tractive force equations (depending on the nature of the riverbed sediments) to estimate the required geometrical characteristics for a given bankfull discharge. A number of examples of river training schemes are illustrated in Jansen et al. (1979).