Disadvantages of River Navigation 151 



AREA OF TRIBUTARIES. 



NAME. COUNTY. LENGTH. BASIN. United length. 



Miles. sq. miles. No. miles. 



Humber . York . . 37 1229 2 55 



Mersey . Lancaster. . 68 1707 6 188 



Nen . . Northampton . 99 1055 l ll 



Ouse . . York . . 59$ 4207 11 629 



Ouse . . Cambridge . 156^ 2894 8 212 



Severn . Gloucester . 178 4437 17 450 



Thames . . 2Oi 5162 15 463 



Trent . . Lincoln . . 167^ 3543 10 293 



Tyne . . Northumberland 35 1053 6 154 



Witham . Lincoln . . 89 1052 4 75 



Wye . . Hereford . . 148 1655 9 223 



In times of heavy storms or of continuous rainy weather, 

 rivers which drain up to 5000 square miles of country may 

 well experience floods involving a serious impediment to 

 navigation. 



The Severn, which brings down to the Bristol Channel so 

 much of the water that falls on Plinlimmon and other Welsh 

 hills, and is joined by various streams, draining, altogether, 

 as shown above, an area of 4437 square miles, is especially 

 liable to floods. In a paper read before the Institution of 

 Civil Engineers in 1860, Mr. E. L. Williams stated that 

 floods had been known to raise the height of the Severn 1 8 ft. 

 in five hours, and they had not infrequently caused it to 

 attain a height of 25 ft. above the level of low water. The 

 Thames and the Trent, also, are particularly liable to floods, 

 and so, down to recent years, when considerable sums were 

 spent on its improvement, was the Weaver. 



It has been asserted in various quarters that less water 

 runs in English rivers now than was probably the case cen- 

 turies ago, when the abundant forests caused a greater rain- 

 fall. This may be so, but, on the other hand, a number of 

 witnesses examined before the Select Committee of 1877 

 expressed the belief that the water flowing into the rivers 

 had increased of recent years, owing to the improved land 

 drainage, which drained off rapidly and sent down to the 

 sea much rain water that previously would have passed into 

 the air again by evaporation. 



In the matter of high tides, " Rees' Cyclopaedia " (1819) 

 says that the tide " often " rises at the mouth of the Wye 



