454 



Dr. C. Callaivay — On River Curves. 



easily explained, since the affluent would not degrade, but deposit. 

 If this supposition is correct, the brook must then have entered on 

 the convex at B. Its current would thus meet the current of the 

 river almost directly, the two opposing forces would cause partial 

 equilibrium, and detritus would be thrown down. As this new land 

 grew, it would push the Severn further and further towards its 

 present position. At a late stage of the process, it would seem as 

 if the opposing currents created the tongue of land CA, so that the 

 brook is forced to fall into the river on the concave at A. 



Fig. 3. — Junction of Cound Brook mth River Severn, showing change of infall on 

 the convex to infall on the concave. 



It is evident that the effects produced at the confluence of a river 

 and its tributary depend on very varied conditions. The most 

 important of these are the angle between them, and their relative 

 magnitude and velocity. It is conceivable, for example, that an 

 affluent, even one of relatively large size, may fall into a river 

 without giving rise to marked curvature. If the main river is 

 flowing swiftly, and the affluent is sluggish, the latter will have too 

 little momentum to materially disturb the momentum of the former. 

 Part of the sediment carried by the tributary would be thrown 

 down at its junction with the river, and the portion which entered 

 the latter would be swept down for a considerable distance. 



On the other hand, if the conditions are favourable to deposit on 

 the opposite bank, an affluent will cause marked divergence of the 

 main stream. This is well seen at the confluence of the Severn 

 with the Tern, of the Wye with the Lug, of the Avon with the 

 Arrow below Stratford, and of the Trent with the Tame. Besides 

 the new deposits on the opposite bank, affluents may also create 

 islands in the main river, as in the Severn at its junction with the 

 Tern, and in the Teme at the infall of the Laughern Brook. Alney 

 Island, at Gloucester, probably originated in this way. It is about 

 two miles in length, with an arm of the Severn running down each 

 side of it. The western arm receives the river Leadon and a smaller 

 stream, while the Hatherly Brook and another affluent enter the 

 eastern branch. The currents of these tributaries coming in on 

 opposites may well have caused a certain amount of dead water, and 

 consequent deposit of sediment. A small island formed in this way 



