RIVER HOG 



course may be greatly improved 

 and shortened by dredging or ex- 

 cavating new channels across sharp 

 Lends. Low level bridges may be 

 raised or replaced by high level 

 bridges, or, where the approach 

 gradients do not permit of this, 

 may be replaced by movable 

 bridges of the swing, lifting, or 

 transporter type. A section of 

 undue width may be reduced and 

 the stream kept within desirable 

 bounds by the construction of con- 

 tinuous banks or detached dykes, 

 which may either be faced with 

 stone set in cement mortar, or be 

 retained by sheet piling or other 

 available means, or may consist of 

 solid masonry walls. 



Where the volume of flow is in- 

 sufficient, it may be possible in cer- 

 tain instances to increase it by di- 

 verting other sources of supply into 

 the stream, but cases are rare in 

 which a serious shortage could be 

 made good in this way. 



River engineering deals with the 

 variation of flow due to alternating 

 periods of drought and floods. 

 Natural river beds are only of suffi- 

 cient capacity to provide for nor- 

 mal discharge ; consequently during 

 floods rivers overflow their natural 

 boundaries and inundate low-lying 

 country. As a result of this and the 

 deposit of sediment brought down 

 from higher levels, some rivers 

 change their courses for consider- 

 able distances from time to time. 



To provide against these effects 

 the following methods may be 

 adopted : ( 1 ) Dams and reservoirs 

 may be constructed, if possible, in 

 the upper regions, by means of which 

 flood water may be stored against 

 the dry season, as in the case of the 

 Assuan dam on the Nile. Such 

 works are usually carried out more 

 particularly in connexion with 

 water supply, irrigation, and can- 

 als. (2) The construction of con- 

 tinuous banks or detached dykes 

 on low-lying sections where flood- 

 ing and erosion occur, may direct 

 the stream into a definite channel. 

 With this must be a system of cross 

 dykes for guiding the flood water 

 back again into the river, and so 

 preventing scour behind the walls. 

 Continuous banks are suitable 

 where ordinary flood water can be 

 entirely contained, but for large 

 rivers the cost is often prohibitive, 

 and detached lengths of dyke are 

 employed, more especially on 

 curved sections, where the centri- 

 fugal force of the current has the 

 worst effect. 



Variations of flow due to tidal 

 range and rapid fall may be cor- 

 rected by the division of a river 

 into sections known as reaches, this 

 being done by the construction of 

 weirs across the waterway at inter- 



6636 



vals determined by the fall. By 

 this means a gentle fall, unaffected 

 by tidal variations, is maintained 

 ^between the weirs, over the crest of 

 which the water discharges itself- 

 into the channel below. The two 

 commonest forms of, weir are solid 

 dams and dams with sluice gates, 

 which may be raised during floods 

 to hasten the discharge of flood 

 water. The weir on the Thames at 

 Richmond was constructed so that 

 at high tide the tidal water rises to 

 water level in the upper reach. At 

 each weir a lock is provided 

 through which boats may pass from 

 one reach to another. In addition 

 to a lock a ramp is occasionally 

 provided, up and down which small 

 craft can be hauled by hand. 



The diversion of a river consists 

 either of deflecting its course into 

 a channel which it previously occu- 

 pied and executing the necessary 

 works to prevent another change of 

 course, or, more frequently, of ex- 

 cavating a new channel. In such 

 cases the new channel is either ex- 

 cavated as far as possible in the 

 dry, the water being admitted on 

 its completion, or the work is per- 

 formed by dredging. See Assuan ; 

 Canal; Dam; Dredging; Irrigation ; 

 Lock; Weir; consult also Rivers 

 and Canals, L. F. Vernon Harcourt, 

 2nd ed. 1896; River and Canal 

 Engineering, E. S. Bellasis, 1913. 



River Hog (Potamochoerus). 

 Species of ungulate mammal 

 found in W. Africa. It has 



River Hog. Species of pig found in 

 herds in the forests of W. Africa 



bright red bristles, and is often 

 known as the red river hog. It 

 occurs in herds in swampy parts 

 of the forests, usually near rivers, 

 and feeds upon plants and roots, 

 often doing great damage in the 

 native plantations. 



Riverina. Dist. of Australia, in 

 New South Wales. It includes all 

 the counties situated between the 

 Lachlan and Murray rivers W. of 

 the meridian of Wagga-Wagga. 

 Entirely a lowland with an average 

 rainfall of 20 ins., and possibilities 

 of irrigation from the Murrum- 

 bidgee and the boundary rivers, 

 and comprising a small artesian 

 basin which yields subterranean 



RIVERS 



water through bores, the Riverina 

 is an excellent wheat-growing 

 area and very suitable for sheep 

 rearing. The Murray red gum is 

 (localised here. Most of the dist. is 

 nearer Melbourne than Sydney, 

 and the rlys. run S. to Melbourne 

 and E. to Goulburn and Sydney. 

 Deniliquin and Hay are the largest. 

 ^ towns of the district. 



River Plate. Combined estuary 

 of the Uruguay and Parana rivers 

 in S. America. It provides an en- 

 trance for merchant ships to the 

 ports serving the vast food-pro- 

 ducing areas of the pampas. See 

 La Plata, Rio de. 



Rivers, EARL. English title 

 held in turn by the families of 

 Woodville and Savage. In 1466 

 it was given to Sir Richard Wood- 

 ville, but it became extinct when 

 the 3rd earl died in 1491. In 1626 

 it was revived for Thomas Darcy, 

 from whom it passed to a grand- 

 son, John Savage, who became the 

 2nd earl in 1640. It remained in 

 the Savage family until the death 

 of the 5th earl, who was a priest, 

 in 1735. It is supposed that the 

 name was first taken from that of 

 a Devonshire family. 



Richard Savage (c. 1660-1712), 

 who became the 4th earl on the 

 death of his father, Thomas, the 

 3rd earl, in 1694, was notorious for 

 his gallantries and debaucheries. 

 He showed himself a soldier of 

 ability in the wars against France, 

 after which he became a general, 

 master-general of the ordnance, 

 and commander-in-chief. He was 

 also an M.P., and as a politician 

 was concerned with the accessions 

 of William of Orange and George I. 

 He is the earl who lived with the 

 countess of Macclesfield, and was 

 claimed as a father by Richard 

 Savagefa.u.). HediedAug. 18, 1712. 



Rivers, RICHARD WOODVILLE, 

 IST EARL (d. 1469). English states- 

 man. Of a Northamptonshire 

 family, he served in the French 

 wars, and made his fortune by 

 marrying Jacquetta of Luxem- 

 bourg, widow of the duke of Bed- 

 ford, regent of France, 1436. Tem- 

 porarily disgraced for his presump- 

 tion, he regained the king's favour, 

 and in 1448 was made a baron. A 

 staunch Lancastrian under 

 Henry VI, he changed sides under 

 Edward IV, and in 1466 became 

 treasurer and was created Earl 

 Rivers, bis daughter Elizabeth 

 having married the king two 

 'years previously. On the defeat 

 of Edward at Edgecot Rivers fell 

 into his enemies' hands and was 

 executed, August 12, 1469. See 

 Lancaster and York, 1399-1485, 

 Sir J. H. Ramsay, 1892; The 

 Paston Letters, ed. J. Gairdner, 

 new ed. 1914. 



